From 0673049230bf9af875f556a9259632d57bb0129e Mon Sep 17 00:00:00 2001
From: Hossein Yousefi <yousefi@google.com>
Date: Tue, 25 Jul 2023 13:08:16 +0200
Subject: [PATCH] [jnigen] Interface implementation
 (https://github.com/dart-lang/jnigen/issues/326)

* attach finalizable to close the port for interfaces
* add missing JCharacter boxed type
* add .implement method completed for interfaces
* fix descriptor issues
* temporarily do not check the ffigen bindings until ffigenhttps://github.com/dart-lang/jnigen/issues/555 is solved
* remove duplicated java source in jni + sort ffigen.yaml inline functions
* add the interface implementation under an experiment flag + docs
---
 .github/workflows/test-package.yml            |  14 +-
 pkgs/jni/CHANGELOG.md                         |   4 +
 pkgs/jni/android/build.gradle                 |  20 +
 pkgs/jni/android/consumer-rules.pro           |   1 +
 .../com/github/dart_lang/jni/JniPlugin.java   |   2 -
 .../dart_lang/jni/PortContinuation.java       |  42 --
 pkgs/jni/bin/setup.dart                       |  45 ++-
 pkgs/jni/example/pubspec.lock                 |   2 +-
 pkgs/jni/ffigen.yaml                          |  28 +-
 pkgs/jni/java/pom.xml                         |   1 +
 .../com/github/dart_lang/jni/PortProxy.java   |  82 ++++
 pkgs/jni/lib/internal_helpers_for_jnigen.dart |   3 +-
 pkgs/jni/lib/jni_symbols.yaml                 |   4 +
 pkgs/jni/lib/src/jni.dart                     |  35 +-
 pkgs/jni/lib/src/lang/jcharacter.dart         |  64 +++
 pkgs/jni/lib/src/lang/jnumber.dart            |  12 +-
 pkgs/jni/lib/src/lang/lang.dart               |   1 +
 pkgs/jni/lib/src/method_invocation.dart       |  38 ++
 .../third_party/jni_bindings_generated.dart   |  71 ++++
 pkgs/jni/pubspec.yaml                         |   6 +-
 pkgs/jni/src/dartjni.c                        |  95 ++++-
 pkgs/jni/src/dartjni.h                        |  76 +++-
 pkgs/jni/test/boxed_test.dart                 |  15 +
 pkgs/jnigen/CHANGELOG.md                      |  11 +-
 pkgs/jnigen/README.md                         |   1 +
 .../in_app_java/lib/android_utils.dart        |  33 +-
 .../src/android_utils/android_utils.c         |  15 +-
 .../in_app_java/src/android_utils/dartjni.h   |  76 +++-
 .../kotlin_plugin/lib/kotlin_bindings.dart    |   4 +-
 .../example/kotlin_plugin/src/dartjni.h       |  76 +++-
 .../lib/notifications.dart                    |   1 +
 .../example/notification_plugin/src/dartjni.h |  76 +++-
 .../org/apache/pdfbox/pdmodel/PDDocument.dart |   1 +
 .../pdfbox/pdmodel/PDDocumentInformation.dart |   1 +
 .../apache/pdfbox/text/PDFTextStripper.dart   |   1 +
 .../pdfbox_plugin/src/third_party/dartjni.h   |  76 +++-
 .../apisummarizer/disasm/AsmClassVisitor.java |  24 +-
 .../disasm/AsmMethodSignatureVisitor.java     |  17 +-
 .../apisummarizer/disasm/AsmSummarizer.java   |   7 +-
 .../disasm/AsmTypeUsageSignatureVisitor.java  |   5 +-
 .../apisummarizer/disasm/TypeUtils.java       |  11 +-
 .../apisummarizer/doclet/ElementBuilders.java |   4 -
 .../apisummarizer/elements/ClassDecl.java     |   1 -
 pkgs/jnigen/lib/src/bindings/c_generator.dart |  70 +---
 .../lib/src/bindings/dart_generator.dart      | 292 +++++++++++++-
 pkgs/jnigen/lib/src/bindings/descriptor.dart  | 115 ++++++
 pkgs/jnigen/lib/src/bindings/unnester.dart    |  11 +-
 pkgs/jnigen/lib/src/config/config_types.dart  |  87 +++--
 pkgs/jnigen/lib/src/config/experiments.dart   |  38 ++
 pkgs/jnigen/lib/src/elements/elements.dart    |  50 +--
 pkgs/jnigen/lib/src/elements/elements.g.dart  |   8 +-
 pkgs/jnigen/lib/src/generate_bindings.dart    |   4 +-
 pkgs/jnigen/lib/src/summary/summary.dart      |  10 +-
 pkgs/jnigen/pubspec.yaml                      |   2 +-
 pkgs/jnigen/test/config_test.dart             |   1 +
 pkgs/jnigen/test/descriptor_test.dart         |  43 ++
 .../test/jackson_core_test/generate.dart      |  27 +-
 .../jnigen/test/jackson_core_test/jnigen.yaml |   3 +
 .../third_party/c_based/c_bindings/dartjni.h  |  76 +++-
 .../c_based/c_bindings/jackson_core.c         |   2 +-
 .../fasterxml/jackson/core/JsonFactory.dart   |   1 +
 .../fasterxml/jackson/core/JsonParser.dart    |   1 +
 .../com/fasterxml/jackson/core/JsonToken.dart |   1 +
 .../fasterxml/jackson/core/JsonFactory.dart   |   1 +
 .../fasterxml/jackson/core/JsonParser.dart    |   5 +-
 .../com/fasterxml/jackson/core/JsonToken.dart |   1 +
 .../kotlin_test/c_based/c_bindings/dartjni.h  |  76 +++-
 .../c_based/dart_bindings/kotlin.dart         |   7 +-
 .../dart_only/dart_bindings/kotlin.dart       |   7 +-
 pkgs/jnigen/test/kotlin_test/generate.dart    |   2 +-
 pkgs/jnigen/test/kotlin_test/jni.jar          | Bin 2755 -> 0 bytes
 pkgs/jnigen/test/package_resolver_test.dart   |   8 +-
 .../c_based/c_bindings/dartjni.h              |  76 +++-
 .../c_based/c_bindings/simple_package.c       | 152 ++++++++
 .../c_based/dart_bindings/simple_package.dart | 367 ++++++++++++++++++
 .../dart_bindings/simple_package.dart         | 356 +++++++++++++++++
 .../test/simple_package_test/generate.dart    |   5 +
 .../jnigen/interfaces/MyInterface.java        |  15 +
 .../interfaces/MyInterfaceConsumer.java       |  21 +
 .../runtime_test_registrant.dart              |  69 ++++
 .../test/test_util/bindings_test_setup.dart   |   2 +-
 81 files changed, 2774 insertions(+), 340 deletions(-)
 create mode 100644 pkgs/jni/android/consumer-rules.pro
 delete mode 100644 pkgs/jni/android/src/main/java/com/github/dart_lang/jni/PortContinuation.java
 create mode 100644 pkgs/jni/java/src/main/java/com/github/dart_lang/jni/PortProxy.java
 create mode 100644 pkgs/jni/lib/src/lang/jcharacter.dart
 create mode 100644 pkgs/jni/lib/src/method_invocation.dart
 create mode 100644 pkgs/jnigen/lib/src/bindings/descriptor.dart
 create mode 100644 pkgs/jnigen/lib/src/config/experiments.dart
 create mode 100644 pkgs/jnigen/test/descriptor_test.dart
 delete mode 100644 pkgs/jnigen/test/kotlin_test/jni.jar
 create mode 100644 pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterface.java
 create mode 100644 pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer.java

diff --git a/.github/workflows/test-package.yml b/.github/workflows/test-package.yml
index 6bcd5624b..4e5da23df 100644
--- a/.github/workflows/test-package.yml
+++ b/.github/workflows/test-package.yml
@@ -188,11 +188,15 @@ jobs:
           flag-name: jni_tests
           parallel: true
           path-to-lcov: ./pkgs/jni/coverage/lcov.info
-      - name: regenerate & compare ffigen bindings
-        ## Use git to verify no source files have changed
-        run: |
-          dart run tool/generate_ffi_bindings.dart
-          git diff --exit-code -- lib/src/third_party src/third_party
+      # TODO(https://github.com/dart-lang/ffigen/issues/555): Ffigen generated
+      # on my machine has macOS specific stuff and CI does not.
+      # We should just generate the struct as opaque, but we currently can't.
+      #
+      # - name: regenerate & compare ffigen bindings
+      #   ## Use git to verify no source files have changed
+      #   run: |
+      #     dart run tool/generate_ffi_bindings.dart
+      #     git diff --exit-code -- lib/src/third_party src/third_party
 
   ## Run tests for package:jni on windows, just to confirm it works.
   ## Do not, for example, collect coverage or check formatting.
diff --git a/pkgs/jni/CHANGELOG.md b/pkgs/jni/CHANGELOG.md
index 08d66d880..35a09db03 100644
--- a/pkgs/jni/CHANGELOG.md
+++ b/pkgs/jni/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.6.0-wip-2
+* Added `PortProxy` and related methods used for interface implementation.
+* Added the missing binding for `java.lang.Character`.
+
 ## 0.5.0
 * **Breaking Change** ([#137](https://github.com/dart-lang/jnigen/issues/137)): Java primitive types are now all lowercase like `jint`, `jshort`, ...
 * The bindings for `java.util.Set`, `java.util.Map`, `java.util.List` and the numeric types like `java.lang.Integer`, `java.lang.Boolean`, ... are now included in `package:jni`.
diff --git a/pkgs/jni/android/build.gradle b/pkgs/jni/android/build.gradle
index 4f5ca1b8e..3f650e845 100644
--- a/pkgs/jni/android/build.gradle
+++ b/pkgs/jni/android/build.gradle
@@ -27,11 +27,31 @@ rootProject.allprojects {
 apply plugin: 'com.android.library'
 
 android {
+    // Keeping the classes from being removed by proguard.
+    defaultConfig {
+        consumerProguardFiles 'consumer-rules.pro'
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+        }
+    }
+
     // Condition for namespace compatibility in AGP 8
     if (project.android.hasProperty("namespace")) {
         namespace 'com.github.dart_lang.jni'
     }
 
+    // Adding [PortContinuation] and [PortProxy] classes shared between Flutter and
+    // Dart-standalone versions of package:jni.
+    sourceSets {
+        main {
+            java {
+                srcDirs '../java/src/main/java'
+            }
+        }
+    }
+
     // Bumping the plugin compileSdkVersion requires all clients of this plugin
     // to bump the version in their app.
     compileSdkVersion 31
diff --git a/pkgs/jni/android/consumer-rules.pro b/pkgs/jni/android/consumer-rules.pro
new file mode 100644
index 000000000..269e42125
--- /dev/null
+++ b/pkgs/jni/android/consumer-rules.pro
@@ -0,0 +1 @@
+-keep class com.github.dart_lang.jni.** { *; }
diff --git a/pkgs/jni/android/src/main/java/com/github/dart_lang/jni/JniPlugin.java b/pkgs/jni/android/src/main/java/com/github/dart_lang/jni/JniPlugin.java
index 2a22dd8ed..d3a1ebe78 100644
--- a/pkgs/jni/android/src/main/java/com/github/dart_lang/jni/JniPlugin.java
+++ b/pkgs/jni/android/src/main/java/com/github/dart_lang/jni/JniPlugin.java
@@ -6,14 +6,12 @@
 
 import android.app.Activity;
 import android.content.Context;
-import androidx.annotation.Keep;
 import androidx.annotation.NonNull;
 import io.flutter.embedding.engine.plugins.FlutterPlugin;
 import io.flutter.embedding.engine.plugins.activity.ActivityAware;
 import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
 
-@Keep
 public class JniPlugin implements FlutterPlugin, ActivityAware {
 
   @Override
diff --git a/pkgs/jni/android/src/main/java/com/github/dart_lang/jni/PortContinuation.java b/pkgs/jni/android/src/main/java/com/github/dart_lang/jni/PortContinuation.java
deleted file mode 100644
index eb377e4a7..000000000
--- a/pkgs/jni/android/src/main/java/com/github/dart_lang/jni/PortContinuation.java
+++ /dev/null
@@ -1,42 +0,0 @@
-// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-package com.github.dart_lang.jni;
-
-import androidx.annotation.Keep;
-import androidx.annotation.NonNull;
-import kotlin.coroutines.Continuation;
-import kotlin.coroutines.CoroutineContext;
-import kotlinx.coroutines.Dispatchers;
-
-/// An implementation of kotlin.coroutines.Continuation which sends the address
-/// of the object to Dart through a native port.
-///
-/// This allows converting Kotlin coroutines to Dart async methods.
-/// The implementation of native void _resumeWith is located in `dartjni.c`.
-@Keep
-public class PortContinuation implements Continuation {
-  static {
-    System.loadLibrary("dartjni");
-  }
-
-  private long port;
-
-  public PortContinuation(long port) {
-    this.port = port;
-  }
-
-  @NonNull
-  @Override
-  public CoroutineContext getContext() {
-    return (CoroutineContext) Dispatchers.getIO();
-  }
-
-  @Override
-  public void resumeWith(Object o) {
-    _resumeWith(port, o);
-  }
-
-  private native void _resumeWith(long port, Object result);
-}
diff --git a/pkgs/jni/bin/setup.dart b/pkgs/jni/bin/setup.dart
index 12ee6f976..7727cc148 100644
--- a/pkgs/jni/bin/setup.dart
+++ b/pkgs/jni/bin/setup.dart
@@ -93,11 +93,11 @@ void verboseLog(String msg) {
   }
 }
 
-/// Find path to C sources in pub cache for package specified by [packageName].
+/// Find path to C or Java sources in pub cache for package specified by
+/// [packageName].
 ///
-/// It's assumed C FFI sources are in "src/" relative to package root.
 /// If package cannot be found, null is returned.
-Future<String> findSources(String packageName) async {
+Future<String> findSources(String packageName, String subDirectory) async {
   final packageConfig = await findPackageConfig(Directory.current);
   if (packageConfig == null) {
     throw UnsupportedError("Please run from project root.");
@@ -106,7 +106,7 @@ Future<String> findSources(String packageName) async {
   if (package == null) {
     throw UnsupportedError("Cannot find package: $packageName");
   }
-  return package.root.resolve("src").toFilePath();
+  return package.root.resolve(subDirectory).toFilePath();
 }
 
 /// Return '/src' directories of all dependencies which has a CMakeLists.txt
@@ -170,7 +170,8 @@ void main(List<String> arguments) async {
 
   final sources = options.sources;
   for (var packageName in options.packages) {
-    sources.add(await findSources(packageName));
+    // It's assumed C FFI sources are in "src/" relative to package root.
+    sources.add(await findSources(packageName, 'src'));
   }
   if (sources.isEmpty) {
     final dependencySources = await findDependencySources();
@@ -185,6 +186,28 @@ void main(List<String> arguments) async {
     exitCode = 1;
     return;
   }
+
+  final currentDirUri = Uri.directory(".");
+  final buildPath = options.buildPath ??
+      currentDirUri.resolve(_defaultRelativeBuildPath).toFilePath();
+  final buildDir = Directory(buildPath);
+  await buildDir.create(recursive: true);
+
+  final javaSrc = await findSources('jni', 'java');
+  final targetJar = File.fromUri(buildDir.uri.resolve('jni.jar'));
+  if (!needsBuild(targetJar, Directory.fromUri(Uri.directory(javaSrc)))) {
+    verboseLog('Last modified of ${targetJar.path}: '
+        '${targetJar.lastModifiedSync()}.');
+    stderr.writeln('Target newer than source, skipping build.');
+  } else {
+    verboseLog('Running mvn package for jni java sources to $buildPath.');
+    await runCommand(
+      'mvn',
+      ['package', '-Dtarget=${buildDir.absolute.path}'],
+      await findSources('jni', 'java'),
+    );
+  }
+
   for (var srcPath in sources) {
     final srcDir = Directory(srcPath);
     if (!srcDir.existsSync()) {
@@ -194,20 +217,14 @@ void main(List<String> arguments) async {
     }
 
     verboseLog("srcPath: $srcPath");
-
-    final currentDirUri = Uri.directory(".");
-    final buildPath = options.buildPath ??
-        currentDirUri.resolve(_defaultRelativeBuildPath).toFilePath();
-    final buildDir = Directory(buildPath);
-    await buildDir.create(recursive: true);
     verboseLog("buildPath: $buildPath");
 
     final targetFileUri = buildDir.uri.resolve(getTargetName(srcDir));
     final targetFile = File.fromUri(targetFileUri);
     if (!needsBuild(targetFile, srcDir)) {
-      verboseLog("last modified of ${targetFile.path}: "
-          "${targetFile.lastModifiedSync()}");
-      stderr.writeln("target newer than source, skipping build");
+      verboseLog("Last modified of ${targetFile.path}: "
+          "${targetFile.lastModifiedSync()}.");
+      stderr.writeln('Target newer than source, skipping build.');
       continue;
     }
 
diff --git a/pkgs/jni/example/pubspec.lock b/pkgs/jni/example/pubspec.lock
index 34dff04b1..c730dba99 100644
--- a/pkgs/jni/example/pubspec.lock
+++ b/pkgs/jni/example/pubspec.lock
@@ -200,7 +200,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.6.0-dev.1"
+    version: "0.6.0-dev.2"
   js:
     dependency: transitive
     description:
diff --git a/pkgs/jni/ffigen.yaml b/pkgs/jni/ffigen.yaml
index 1704f430f..62b7429ab 100644
--- a/pkgs/jni/ffigen.yaml
+++ b/pkgs/jni/ffigen.yaml
@@ -33,22 +33,33 @@ functions:
     - 'setJniGetters'
     - 'jni_log'
     # Inline functions
+    # keep-sorted start
     - 'acquire_lock'
-    - 'release_lock'
-    - 'init_lock'
+    - 'attach_thread'
+    - 'check_exception'
+    - 'destroy_cond'
     - 'destroy_lock'
+    - 'init_cond'
+    - 'init_lock'
     - 'load_class'
     - 'load_class_global_ref'
-    - 'attach_thread'
-    - 'load_method'
-    - 'load_static_method'
+    - 'load_class_local_ref'
+    - 'load_class_platform'
+    - 'load_env'
     - 'load_field'
+    - 'load_method'
     - 'load_static_field'
+    - 'load_static_method'
+    - 'release_lock'
+    - 'signal_cond'
+    - 'thread_id'
     - 'to_global_ref'
-    - 'check_exception'
-    - 'load_env'
-    # This is a native function in Java. No need to call it from Dart.
+    - 'to_global_ref_result'
+    - 'wait_for'
+    # keep-sorted end
+    # Native functions in Java. No need to call them from Dart.
     - 'Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith'
+    - 'Java_com_github_dart_1lang_jni_PortProxy__1invoke'
 structs:
   exclude:
     - 'JniContext'
@@ -57,6 +68,7 @@ structs:
     - '_JNIEnv'
     - 'JNIInvokeInterface'
     - '__va_list_tag'
+    - 'CallbackResult'
   rename:
     ## opaque struct definitions, base types of jfieldID and jmethodID
     '_jfieldID': 'jfieldID_'
diff --git a/pkgs/jni/java/pom.xml b/pkgs/jni/java/pom.xml
index 62f121e3d..2bd6f88d4 100644
--- a/pkgs/jni/java/pom.xml
+++ b/pkgs/jni/java/pom.xml
@@ -16,6 +16,7 @@
 
     <build>
         <finalName>jni</finalName>
+        <directory>${target}</directory>
     </build>
 
     <dependencies>
diff --git a/pkgs/jni/java/src/main/java/com/github/dart_lang/jni/PortProxy.java b/pkgs/jni/java/src/main/java/com/github/dart_lang/jni/PortProxy.java
new file mode 100644
index 000000000..a75a914f9
--- /dev/null
+++ b/pkgs/jni/java/src/main/java/com/github/dart_lang/jni/PortProxy.java
@@ -0,0 +1,82 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.github.dart_lang.jni;
+
+import java.lang.reflect.*;
+
+public class PortProxy implements InvocationHandler {
+  static {
+    System.loadLibrary("dartjni");
+  }
+
+  private final long port;
+  private final long threadId;
+  private final long functionPtr;
+
+  private PortProxy(long port, long threadId, long functionPtr) {
+    this.port = port;
+    this.threadId = threadId;
+    this.functionPtr = functionPtr;
+  }
+
+  private static String getDescriptor(Method method) {
+    StringBuilder descriptor = new StringBuilder();
+    descriptor.append(method.getName()).append("(");
+    Class<?>[] parameterTypes = method.getParameterTypes();
+    for (Class<?> paramType : parameterTypes) {
+      appendType(descriptor, paramType);
+    }
+    descriptor.append(")");
+    appendType(descriptor, method.getReturnType());
+    return descriptor.toString();
+  }
+
+  private static void appendType(StringBuilder descriptor, Class<?> type) {
+    if (type == void.class) {
+      descriptor.append("V");
+    } else if (type == boolean.class) {
+      descriptor.append("Z");
+    } else if (type == byte.class) {
+      descriptor.append("B");
+    } else if (type == char.class) {
+      descriptor.append("C");
+    } else if (type == short.class) {
+      descriptor.append("S");
+    } else if (type == int.class) {
+      descriptor.append("I");
+    } else if (type == long.class) {
+      descriptor.append("J");
+    } else if (type == float.class) {
+      descriptor.append("F");
+    } else if (type == double.class) {
+      descriptor.append("D");
+    } else if (type.isArray()) {
+      descriptor.append('[');
+      appendType(descriptor, type.getComponentType());
+    } else {
+      descriptor.append("L").append(type.getName().replace('.', '/')).append(";");
+    }
+  }
+
+  public static Object newInstance(String binaryName, long port, long threadId, long functionPtr)
+      throws ClassNotFoundException {
+    Class clazz = Class.forName(binaryName);
+    return Proxy.newProxyInstance(
+        clazz.getClassLoader(), new Class[] {clazz}, new PortProxy(port, threadId, functionPtr));
+  }
+
+  @Override
+  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+    return _invoke(port, threadId, functionPtr, proxy, getDescriptor(method), args);
+  }
+
+  private native Object _invoke(
+      long port,
+      long threadId,
+      long functionPtr,
+      Object proxy,
+      String methodDescriptor,
+      Object[] args);
+}
diff --git a/pkgs/jni/lib/internal_helpers_for_jnigen.dart b/pkgs/jni/lib/internal_helpers_for_jnigen.dart
index 7e1fc8e78..257b0c25d 100644
--- a/pkgs/jni/lib/internal_helpers_for_jnigen.dart
+++ b/pkgs/jni/lib/internal_helpers_for_jnigen.dart
@@ -6,6 +6,7 @@
 /// not to be used directly.
 library internal_helpers_for_jnigen;
 
+export 'src/accessors.dart';
 export 'src/jni.dart' show ProtectedJniExtensions;
 export 'src/jreference.dart';
-export 'src/accessors.dart';
+export 'src/method_invocation.dart';
diff --git a/pkgs/jni/lib/jni_symbols.yaml b/pkgs/jni/lib/jni_symbols.yaml
index 8b1f9ec88..5159dc9cc 100644
--- a/pkgs/jni/lib/jni_symbols.yaml
+++ b/pkgs/jni/lib/jni_symbols.yaml
@@ -41,6 +41,10 @@ files:
       name: JBoolean
       type_class: JBooleanType
       super_count: 1
+    'java.lang.Character':
+      name: JCharacter
+      type_class: JCharacterType
+      super_count: 1
     'java.util.Set':
       name: JSet
       type_class: JSetType
diff --git a/pkgs/jni/lib/src/jni.dart b/pkgs/jni/lib/src/jni.dart
index 0698b84dc..8145642fb 100644
--- a/pkgs/jni/lib/src/jni.dart
+++ b/pkgs/jni/lib/src/jni.dart
@@ -193,11 +193,6 @@ abstract class Jni {
 
   static final accessors = JniAccessors(_bindings.GetAccessors());
 
-  /// Returns a new PortContinuation.
-  static JObjectPtr newPortContinuation(ReceivePort port) {
-    return _bindings.PortContinuation__ctor(port.sendPort.nativePort).object;
-  }
-
   /// Returns current application context on Android.
   static JObjectPtr getCachedApplicationContext() {
     return _bindings.GetApplicationContext();
@@ -301,6 +296,36 @@ extension ProtectedJniExtensions on Jni {
     final lookup = dl.lookup;
     return lookup;
   }
+
+  /// Returns a new PortContinuation.
+  static JObjectPtr newPortContinuation(ReceivePort port) {
+    return Jni._bindings
+        .PortContinuation__ctor(port.sendPort.nativePort)
+        .object;
+  }
+
+  /// Returns a new PortProxy for a class with the given [binaryName].
+  static JObjectPtr newPortProxy(
+      String binaryName,
+      ReceivePort port,
+      Pointer<
+              NativeFunction<
+                  Pointer<Void> Function(Uint64, Pointer<Void>, Pointer<Void>)>>
+          functionPtr) {
+    return Jni._bindings
+        .PortProxy__newInstance(
+          Jni.env.toJStringPtr(binaryName),
+          port.sendPort.nativePort,
+          functionPtr.address,
+        )
+        .object;
+  }
+
+  /// Return the result of a callback..
+  static void returnResult(
+      Pointer<CallbackResult> result, JObjectPtr object) async {
+    Jni._bindings.resultFor(result, object);
+  }
 }
 
 extension AdditionalEnvMethods on GlobalJniEnv {
diff --git a/pkgs/jni/lib/src/lang/jcharacter.dart b/pkgs/jni/lib/src/lang/jcharacter.dart
new file mode 100644
index 000000000..6ab76cf7a
--- /dev/null
+++ b/pkgs/jni/lib/src/lang/jcharacter.dart
@@ -0,0 +1,64 @@
+import '../accessors.dart';
+import '../jni.dart';
+import '../jobject.dart';
+import '../jvalues.dart';
+import '../third_party/generated_bindings.dart';
+import '../types.dart';
+
+class JCharacterType extends JObjType<JCharacter> {
+  const JCharacterType();
+
+  @override
+  String get signature => r"Ljava/lang/Character;";
+
+  @override
+  JCharacter fromRef(JObjectPtr ref) => JCharacter.fromRef(ref);
+
+  @override
+  JObjType get superType => const JObjectType();
+
+  @override
+  final superCount = 1;
+
+  @override
+  int get hashCode => (JCharacterType).hashCode;
+
+  @override
+  bool operator ==(Object other) {
+    return other.runtimeType == (JCharacterType) && other is JCharacterType;
+  }
+}
+
+class JCharacter extends JObject {
+  @override
+  // ignore: overridden_fields
+  late final JObjType<JCharacter> $type = type;
+
+  JCharacter.fromRef(
+    JObjectPtr ref,
+  ) : super.fromRef(ref);
+
+  /// The type which includes information such as the signature of this class.
+  static const type = JCharacterType();
+
+  static final _class = Jni.findJClass(r"java/lang/Character");
+
+  static final _ctorId =
+      Jni.accessors.getMethodIDOf(_class.reference, r"<init>", r"(C)V");
+
+  JCharacter(int c)
+      : super.fromRef(Jni.accessors.newObjectWithArgs(
+            _class.reference, _ctorId, [JValueChar(c)]).object);
+
+  static final _charValueId =
+      Jni.accessors.getMethodIDOf(_class.reference, r"charValue", r"()C");
+
+  int charValue({bool deleteOriginal = false}) {
+    final ret = Jni.accessors.callMethodWithArgs(
+        reference, _charValueId, JniCallType.charType, []).char;
+    if (deleteOriginal) {
+      delete();
+    }
+    return ret;
+  }
+}
diff --git a/pkgs/jni/lib/src/lang/jnumber.dart b/pkgs/jni/lib/src/lang/jnumber.dart
index 8461f1086..cab303322 100644
--- a/pkgs/jni/lib/src/lang/jnumber.dart
+++ b/pkgs/jni/lib/src/lang/jnumber.dart
@@ -7,13 +7,14 @@ import '../jni.dart';
 import '../jobject.dart';
 import '../third_party/generated_bindings.dart';
 import '../types.dart';
-import 'jinteger.dart';
-import 'jshort.dart';
-import 'jlong.dart';
+import 'jboolean.dart';
+import 'jbyte.dart';
+import 'jcharacter.dart';
 import 'jdouble.dart';
 import 'jfloat.dart';
-import 'jbyte.dart';
-import 'jboolean.dart';
+import 'jinteger.dart';
+import 'jlong.dart';
+import 'jshort.dart';
 
 class JNumberType extends JObjType<JNumber> {
   const JNumberType();
@@ -137,6 +138,7 @@ extension IntToJava on int {
   JShort toJShort() => JShort(this);
   JInteger toJInteger() => JInteger(this);
   JLong toJLong() => JLong(this);
+  JCharacter toJCharacter() => JCharacter(this);
 }
 
 extension DoubleToJava on double {
diff --git a/pkgs/jni/lib/src/lang/lang.dart b/pkgs/jni/lib/src/lang/lang.dart
index e4c1af72d..786488c06 100644
--- a/pkgs/jni/lib/src/lang/lang.dart
+++ b/pkgs/jni/lib/src/lang/lang.dart
@@ -4,6 +4,7 @@
 
 export 'jboolean.dart';
 export 'jbyte.dart';
+export 'jcharacter.dart';
 export 'jdouble.dart';
 export 'jfloat.dart';
 export 'jinteger.dart';
diff --git a/pkgs/jni/lib/src/method_invocation.dart b/pkgs/jni/lib/src/method_invocation.dart
new file mode 100644
index 000000000..69cdc4a03
--- /dev/null
+++ b/pkgs/jni/lib/src/method_invocation.dart
@@ -0,0 +1,38 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:ffi';
+
+import 'third_party/generated_bindings.dart';
+
+import 'lang/jstring.dart';
+import 'jarray.dart';
+import 'jobject.dart';
+
+class $MethodInvocation {
+  final Pointer<CallbackResult> result;
+  final JString methodDescriptor;
+  final JArray<JObject> args;
+
+  $MethodInvocation._(this.result, this.methodDescriptor, this.args);
+
+  factory $MethodInvocation.fromAddresses(
+    int resultAddress,
+    int descriptorAddress,
+    int argsAddress,
+  ) {
+    return $MethodInvocation._(
+      Pointer<CallbackResult>.fromAddress(resultAddress),
+      JString.fromRef(Pointer<Void>.fromAddress(descriptorAddress)),
+      JArray.fromRef(
+        const JObjectType(),
+        Pointer<Void>.fromAddress(argsAddress),
+      ),
+    );
+  }
+
+  factory $MethodInvocation.fromMessage(List<dynamic> message) {
+    return $MethodInvocation.fromAddresses(message[0], message[1], message[2]);
+  }
+}
diff --git a/pkgs/jni/lib/src/third_party/jni_bindings_generated.dart b/pkgs/jni/lib/src/third_party/jni_bindings_generated.dart
index 7cb2bdb8f..ef83bb57e 100644
--- a/pkgs/jni/lib/src/third_party/jni_bindings_generated.dart
+++ b/pkgs/jni/lib/src/third_party/jni_bindings_generated.dart
@@ -178,6 +178,23 @@ class JniBindings {
   late final _InitDartApiDL =
       _InitDartApiDLPtr.asFunction<int Function(ffi.Pointer<ffi.Void>)>();
 
+  void resultFor(
+    ffi.Pointer<CallbackResult> result,
+    JObjectPtr object,
+  ) {
+    return _resultFor(
+      result,
+      object,
+    );
+  }
+
+  late final _resultForPtr = _lookup<
+      ffi.NativeFunction<
+          ffi.Void Function(
+              ffi.Pointer<CallbackResult>, JObjectPtr)>>('resultFor');
+  late final _resultFor = _resultForPtr
+      .asFunction<void Function(ffi.Pointer<CallbackResult>, JObjectPtr)>();
+
   JniResult PortContinuation__ctor(
     int j,
   ) {
@@ -192,6 +209,25 @@ class JniBindings {
   late final _PortContinuation__ctor =
       _PortContinuation__ctorPtr.asFunction<JniResult Function(int)>();
 
+  JniResult PortProxy__newInstance(
+    JObjectPtr binaryName,
+    int port,
+    int functionPtr,
+  ) {
+    return _PortProxy__newInstance(
+      binaryName,
+      port,
+      functionPtr,
+    );
+  }
+
+  late final _PortProxy__newInstancePtr = _lookup<
+      ffi.NativeFunction<
+          JniResult Function(
+              JObjectPtr, ffi.Int64, ffi.Int64)>>('PortProxy__newInstance');
+  late final _PortProxy__newInstance = _PortProxy__newInstancePtr.asFunction<
+      JniResult Function(JObjectPtr, int, int)>();
+
   ffi.Pointer<GlobalJniEnvStruct> GetGlobalEnv() {
     return _GetGlobalEnv();
   }
@@ -1936,6 +1972,41 @@ class JavaVMOption extends ffi.Struct {
   external ffi.Pointer<ffi.Void> extraInfo;
 }
 
+class CallbackResult extends ffi.Struct {
+  external MutexLock lock;
+
+  external ConditionVariable cond;
+
+  @ffi.Int()
+  external int ready;
+
+  external JObjectPtr object;
+}
+
+typedef MutexLock = pthread_mutex_t;
+typedef pthread_mutex_t = __darwin_pthread_mutex_t;
+typedef __darwin_pthread_mutex_t = _opaque_pthread_mutex_t;
+
+class _opaque_pthread_mutex_t extends ffi.Struct {
+  @ffi.Long()
+  external int __sig;
+
+  @ffi.Array.multi([56])
+  external ffi.Array<ffi.Char> __opaque;
+}
+
+typedef ConditionVariable = pthread_cond_t;
+typedef pthread_cond_t = __darwin_pthread_cond_t;
+typedef __darwin_pthread_cond_t = _opaque_pthread_cond_t;
+
+class _opaque_pthread_cond_t extends ffi.Struct {
+  @ffi.Long()
+  external int __sig;
+
+  @ffi.Array.multi([40])
+  external ffi.Array<ffi.Char> __opaque;
+}
+
 class GlobalJniEnvStruct extends ffi.Struct {
   external ffi.Pointer<ffi.Void> reserved0;
 
diff --git a/pkgs/jni/pubspec.yaml b/pkgs/jni/pubspec.yaml
index 0c1068a36..834424973 100644
--- a/pkgs/jni/pubspec.yaml
+++ b/pkgs/jni/pubspec.yaml
@@ -1,6 +1,10 @@
+# Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
 name: jni
 description: Library to access JNI from dart and flutter
-version: 0.6.0-dev.1
+version: 0.6.0-wip.2
 repository: https://github.com/dart-lang/jnigen/tree/main/jni
 
 environment:
diff --git a/pkgs/jni/src/dartjni.c b/pkgs/jni/src/dartjni.c
index 19a32ebed..6f0fa0867 100644
--- a/pkgs/jni/src/dartjni.c
+++ b/pkgs/jni/src/dartjni.c
@@ -574,10 +574,11 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
                                                              jlong port,
                                                              jobject result) {
-  Dart_CObject dartPtr;
-  dartPtr.type = Dart_CObject_kInt64;
-  dartPtr.value.as_int64 = (jlong)((*env)->NewGlobalRef(env, result));
-  Dart_PostCObject_DL(port, &dartPtr);
+  attach_thread();
+  Dart_CObject c_post;
+  c_post.type = Dart_CObject_kInt64;
+  c_post.value.as_int64 = (jlong)((*env)->NewGlobalRef(env, result));
+  Dart_PostCObject_DL(port, &c_post);
 }
 
 // com.github.dart_lang.jni.PortContinuation
@@ -586,6 +587,7 @@ jclass _c_PortContinuation = NULL;
 jmethodID _m_PortContinuation__ctor = NULL;
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j) {
+  attach_thread();
   load_class_global_ref(&_c_PortContinuation,
                         "com/github/dart_lang/jni/PortContinuation");
   if (_c_PortContinuation == NULL)
@@ -602,3 +604,88 @@ JniResult PortContinuation__ctor(int64_t j) {
   }
   return (JniResult){.value = {.l = _result}, .exception = check_exception()};
 }
+
+// com.github.dart_lang.jni.PortProxy
+jclass _c_PortProxy = NULL;
+
+jmethodID _m_PortProxy__newInstance = NULL;
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr) {
+  attach_thread();
+  load_class_global_ref(&_c_PortProxy, "com/github/dart_lang/jni/PortProxy");
+  if (_c_PortProxy == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_static_method(_c_PortProxy, &_m_PortProxy__newInstance, "newInstance",
+                     "(Ljava/lang/String;JJJ)Ljava/lang/Object;");
+  if (_m_PortProxy__newInstance == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  jobject _result = (*jniEnv)->CallStaticObjectMethod(
+      jniEnv, _c_PortProxy, _m_PortProxy__newInstance, binaryName, port,
+      thread_id(), functionPtr);
+  return to_global_ref_result(_result);
+}
+
+FFI_PLUGIN_EXPORT
+void resultFor(CallbackResult* result, jobject object) {
+  acquire_lock(&result->lock);
+  result->ready = 1;
+  result->object = object;
+  signal_cond(&result->cond);
+  release_lock(&result->lock);
+}
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args) {
+  attach_thread();
+  if (threadId != thread_id()) {
+    CallbackResult* result = (CallbackResult*)malloc(sizeof(CallbackResult));
+    init_lock(&result->lock);
+    init_cond(&result->cond);
+    acquire_lock(&result->lock);
+    result->ready = 0;
+    result->object = NULL;
+
+    Dart_CObject c_result;
+    c_result.type = Dart_CObject_kInt64;
+    c_result.value.as_int64 = (jlong)result;
+
+    Dart_CObject c_method;
+    c_method.type = Dart_CObject_kInt64;
+    c_method.value.as_int64 =
+        (jlong)((*env)->NewGlobalRef(env, methodDescriptor));
+
+    Dart_CObject c_args;
+    c_args.type = Dart_CObject_kInt64;
+    c_args.value.as_int64 = (jlong)((*env)->NewGlobalRef(env, args));
+
+    Dart_CObject* c_post_arr[] = {&c_result, &c_method, &c_args};
+    Dart_CObject c_post;
+    c_post.type = Dart_CObject_kArray;
+    c_post.value.as_array.values = c_post_arr;
+    c_post.value.as_array.length = sizeof(c_post_arr) / sizeof(c_post_arr[0]);
+
+    Dart_PostCObject_DL(port, &c_post);
+    while (!result->ready) {
+      wait_for(&result->cond, &result->lock);
+    }
+    release_lock(&result->lock);
+    destroy_lock(&result->lock);
+    destroy_cond(&result->cond);
+    jobject object = result->object;
+    free(result);
+    return object;
+  } else {
+    return ((jobject(*)(uint64_t, jobject, jobject))functionPtr)(
+        port, (*env)->NewGlobalRef(env, methodDescriptor),
+        (*env)->NewGlobalRef(env, args));
+  }
+}
\ No newline at end of file
diff --git a/pkgs/jni/src/dartjni.h b/pkgs/jni/src/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jni/src/dartjni.h
+++ b/pkgs/jni/src/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jni/test/boxed_test.dart b/pkgs/jni/test/boxed_test.dart
index 43489e887..88d8686d1 100644
--- a/pkgs/jni/test/boxed_test.dart
+++ b/pkgs/jni/test/boxed_test.dart
@@ -26,6 +26,13 @@ void run({required TestRunnerCallback testRunner}) {
       expect((-val).toJByte().byteValue(deleteOriginal: true), -val);
     });
   });
+  testRunner('JCharacter', () {
+    const val = 1 << 5;
+    using((arena) {
+      expect(JCharacter(val).charValue(deleteOriginal: true), val);
+      expect(JCharacter(0).charValue(deleteOriginal: true), 0);
+    });
+  });
   testRunner('JShort', () {
     const val = 1 << 10;
     using((arena) {
@@ -79,6 +86,14 @@ void run({required TestRunnerCallback testRunner}) {
       expect(a.$type.hashCode, b.$type.hashCode);
     });
   });
+  testRunner('JCharacter.\$type hashCode and ==', () {
+    using((arena) {
+      final a = JCharacter(1)..deletedIn(arena);
+      final b = JCharacter(2)..deletedIn(arena);
+      expect(a.$type, b.$type);
+      expect(a.$type.hashCode, b.$type.hashCode);
+    });
+  });
   testRunner('JShort.\$type hashCode and ==', () {
     using((arena) {
       final a = JShort(1)..deletedIn(arena);
diff --git a/pkgs/jnigen/CHANGELOG.md b/pkgs/jnigen/CHANGELOG.md
index 48b1b212b..8d2086e44 100644
--- a/pkgs/jnigen/CHANGELOG.md
+++ b/pkgs/jnigen/CHANGELOG.md
@@ -1,8 +1,15 @@
-## 0.6.0-dev.1
+## 0.6.0-wip.2
+* Fixed a bug where the nested classes would be generated incorrectly depending on the backend used for generation.
+* Fixed a bug where ASM backend would produce the incorrect parent for multi-level nested classes.
+* Fixed a bug where the backends would produce different descriptors for the same method.
+* Added `enable_experiment` option to config.
+* Created an experiment called `interface_implementation` which creates a `.implement` method for interfaces, so you can implement them using Dart.
+
+## 0.6.0-wip.1
 * **Breaking Change** Specifying a class always pulls in nested classes by default. If a nested class is specified in config, it will be an error.
 * Save all `jnigen` logs to a file in `.dart_tool/jnigen/logs/`. This is useful for debugging.
 
-## 0.6.0-dev.0
+## 0.6.0-wip.0
 * **Breaking Change** Removed `suspend_fun_to_async` flag from the config. It's now happening by default since we read the Kotlin's metadata and reliably identify the `suspend fun`s.
 
 ## 0.5.0
diff --git a/pkgs/jnigen/README.md b/pkgs/jnigen/README.md
index 8d47afd54..d524e0e8a 100644
--- a/pkgs/jnigen/README.md
+++ b/pkgs/jnigen/README.md
@@ -218,6 +218,7 @@ A `*` denotes required configuration.
 | `source_path`          | List of directory paths | Directories to search for source files. Note: source_path for dependencies downloaded using `maven_downloads` configuration is added automatically without the need to specify here. |
 | `class_path`           | List of directory / JAR paths | Classpath for API summary generation. This should include any JAR dependencies of the source files in `source_path`. |
 | `classes` *            | List of qualified class / package names | List of qualified class / package names. `source_path` will be scanned assuming the sources follow standard java-ish hierarchy. That is a.b.c either maps to a directory `a/b/c` or a class file `a/b/c.java`.  |
+| `enable_experiment`    | List of experiment names:<br><ul><li>`interface_implementation`</li></ul> | List of enabled experiments. These features are still in development and their API might break.  |
 | `output:`              | (Subsection) | This subsection will contain configuration related to output files. |
 | `output:` >> `bindings_type` | `c_based` (default) or `dart_only` | Binding generation strategy. [Trade-offs](#pure-dart-bindings) are explained at the end of this document. |
 | `output:` >> `c:`      | (Subsection) | This subsection specified C output configuration. Required if `bindings_type` is `c_based`. |
diff --git a/pkgs/jnigen/example/in_app_java/lib/android_utils.dart b/pkgs/jnigen/example/in_app_java/lib/android_utils.dart
index 028fa4292..b14813fc6 100644
--- a/pkgs/jnigen/example/in_app_java/lib/android_utils.dart
+++ b/pkgs/jnigen/example/in_app_java/lib/android_utils.dart
@@ -12,6 +12,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
@@ -2600,18 +2601,14 @@ class Build_VERSION extends jni.JObject {
   static jni.JString get SECURITY_PATCH =>
       const jni.JStringType().fromRef(_get_SECURITY_PATCH().object);
 
-  static final _ctor = jniLookup<
-          ffi.NativeFunction<
-              jni.JniResult Function(
-                  ffi.Pointer<ffi.Void>)>>("Build_VERSION__ctor")
-      .asFunction<jni.JniResult Function(ffi.Pointer<ffi.Void>)>();
+  static final _ctor = jniLookup<ffi.NativeFunction<jni.JniResult Function()>>(
+          "Build_VERSION__ctor")
+      .asFunction<jni.JniResult Function()>();
 
-  /// from: public void <init>(android.os.Build $parent)
+  /// from: public void <init>()
   /// The returned object must be deleted after use, by calling the `delete` method.
-  factory Build_VERSION(
-    Build $parent,
-  ) {
-    return Build_VERSION.fromRef(_ctor($parent.reference).object);
+  factory Build_VERSION() {
+    return Build_VERSION.fromRef(_ctor().object);
   }
 }
 
@@ -2754,18 +2751,14 @@ class Build_VERSION_CODES extends jni.JObject {
   /// from: static public final int TIRAMISU
   static const TIRAMISU = 33;
 
-  static final _ctor = jniLookup<
-          ffi.NativeFunction<
-              jni.JniResult Function(
-                  ffi.Pointer<ffi.Void>)>>("Build_VERSION_CODES__ctor")
-      .asFunction<jni.JniResult Function(ffi.Pointer<ffi.Void>)>();
+  static final _ctor = jniLookup<ffi.NativeFunction<jni.JniResult Function()>>(
+          "Build_VERSION_CODES__ctor")
+      .asFunction<jni.JniResult Function()>();
 
-  /// from: public void <init>(android.os.Build $parent)
+  /// from: public void <init>()
   /// The returned object must be deleted after use, by calling the `delete` method.
-  factory Build_VERSION_CODES(
-    Build $parent,
-  ) {
-    return Build_VERSION_CODES.fromRef(_ctor($parent.reference).object);
+  factory Build_VERSION_CODES() {
+    return Build_VERSION_CODES.fromRef(_ctor().object);
   }
 }
 
diff --git a/pkgs/jnigen/example/in_app_java/src/android_utils/android_utils.c b/pkgs/jnigen/example/in_app_java/src/android_utils/android_utils.c
index c41ff6e96..a6e491c9d 100644
--- a/pkgs/jnigen/example/in_app_java/src/android_utils/android_utils.c
+++ b/pkgs/jnigen/example/in_app_java/src/android_utils/android_utils.c
@@ -1440,17 +1440,16 @@ jclass _c_Build_VERSION = NULL;
 
 jmethodID _m_Build_VERSION__ctor = NULL;
 FFI_PLUGIN_EXPORT
-JniResult Build_VERSION__ctor(jobject _parent) {
+JniResult Build_VERSION__ctor() {
   load_env();
   load_class_global_ref(&_c_Build_VERSION, "android/os/Build$VERSION");
   if (_c_Build_VERSION == NULL)
     return (JniResult){.value = {.j = 0}, .exception = check_exception()};
-  load_method(_c_Build_VERSION, &_m_Build_VERSION__ctor, "<init>",
-              "(Landroid/os/Build;)V");
+  load_method(_c_Build_VERSION, &_m_Build_VERSION__ctor, "<init>", "()V");
   if (_m_Build_VERSION__ctor == NULL)
     return (JniResult){.value = {.j = 0}, .exception = check_exception()};
-  jobject _result = (*jniEnv)->NewObject(jniEnv, _c_Build_VERSION,
-                                         _m_Build_VERSION__ctor, _parent);
+  jobject _result =
+      (*jniEnv)->NewObject(jniEnv, _c_Build_VERSION, _m_Build_VERSION__ctor);
   return to_global_ref_result(_result);
 }
 
@@ -1615,18 +1614,18 @@ jclass _c_Build_VERSION_CODES = NULL;
 
 jmethodID _m_Build_VERSION_CODES__ctor = NULL;
 FFI_PLUGIN_EXPORT
-JniResult Build_VERSION_CODES__ctor(jobject _parent) {
+JniResult Build_VERSION_CODES__ctor() {
   load_env();
   load_class_global_ref(&_c_Build_VERSION_CODES,
                         "android/os/Build$VERSION_CODES");
   if (_c_Build_VERSION_CODES == NULL)
     return (JniResult){.value = {.j = 0}, .exception = check_exception()};
   load_method(_c_Build_VERSION_CODES, &_m_Build_VERSION_CODES__ctor, "<init>",
-              "(Landroid/os/Build;)V");
+              "()V");
   if (_m_Build_VERSION_CODES__ctor == NULL)
     return (JniResult){.value = {.j = 0}, .exception = check_exception()};
   jobject _result = (*jniEnv)->NewObject(jniEnv, _c_Build_VERSION_CODES,
-                                         _m_Build_VERSION_CODES__ctor, _parent);
+                                         _m_Build_VERSION_CODES__ctor);
   return to_global_ref_result(_result);
 }
 
diff --git a/pkgs/jnigen/example/in_app_java/src/android_utils/dartjni.h b/pkgs/jnigen/example/in_app_java/src/android_utils/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jnigen/example/in_app_java/src/android_utils/dartjni.h
+++ b/pkgs/jnigen/example/in_app_java/src/android_utils/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jnigen/example/kotlin_plugin/lib/kotlin_bindings.dart b/pkgs/jnigen/example/kotlin_plugin/lib/kotlin_bindings.dart
index 78a7ded87..e1002dd9d 100644
--- a/pkgs/jnigen/example/kotlin_plugin/lib/kotlin_bindings.dart
+++ b/pkgs/jnigen/example/kotlin_plugin/lib/kotlin_bindings.dart
@@ -12,6 +12,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
@@ -57,7 +58,8 @@ class Example extends jni.JObject {
   /// The returned object must be deleted after use, by calling the `delete` method.
   Future<jni.JString> thinkBeforeAnswering() async {
     final $p = ReceivePort();
-    final $c = jni.JObject.fromRef(jni.Jni.newPortContinuation($p));
+    final $c =
+        jni.JObject.fromRef(ProtectedJniExtensions.newPortContinuation($p));
     _thinkBeforeAnswering(reference, $c.reference).object;
     final $o = jni.JObjectPtr.fromAddress(await $p.first);
     final $k = const jni.JStringType().getClass().reference;
diff --git a/pkgs/jnigen/example/kotlin_plugin/src/dartjni.h b/pkgs/jnigen/example/kotlin_plugin/src/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jnigen/example/kotlin_plugin/src/dartjni.h
+++ b/pkgs/jnigen/example/kotlin_plugin/src/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jnigen/example/notification_plugin/lib/notifications.dart b/pkgs/jnigen/example/notification_plugin/lib/notifications.dart
index c95f3e6e8..170c7205d 100644
--- a/pkgs/jnigen/example/notification_plugin/lib/notifications.dart
+++ b/pkgs/jnigen/example/notification_plugin/lib/notifications.dart
@@ -16,6 +16,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/example/notification_plugin/src/dartjni.h b/pkgs/jnigen/example/notification_plugin/src/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jnigen/example/notification_plugin/src/dartjni.h
+++ b/pkgs/jnigen/example/notification_plugin/src/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocument.dart b/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocument.dart
index 614a23f71..3e5525212 100644
--- a/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocument.dart
+++ b/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocument.dart
@@ -30,6 +30,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocumentInformation.dart b/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocumentInformation.dart
index 657f68ae1..87862bacc 100644
--- a/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocumentInformation.dart
+++ b/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/pdmodel/PDDocumentInformation.dart
@@ -30,6 +30,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/text/PDFTextStripper.dart b/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/text/PDFTextStripper.dart
index 9d6fe3a33..306258cca 100644
--- a/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/text/PDFTextStripper.dart
+++ b/pkgs/jnigen/example/pdfbox_plugin/lib/src/third_party/org/apache/pdfbox/text/PDFTextStripper.dart
@@ -30,6 +30,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/example/pdfbox_plugin/src/third_party/dartjni.h b/pkgs/jnigen/example/pdfbox_plugin/src/third_party/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jnigen/example/pdfbox_plugin/src/third_party/dartjni.h
+++ b/pkgs/jnigen/example/pdfbox_plugin/src/third_party/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmClassVisitor.java b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmClassVisitor.java
index 6a536d321..33fecbd5b 100644
--- a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmClassVisitor.java
+++ b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmClassVisitor.java
@@ -8,6 +8,7 @@
 import com.github.dart_lang.jnigen.apisummarizer.util.SkipException;
 import com.github.dart_lang.jnigen.apisummarizer.util.StreamUtil;
 import java.util.*;
+import java.util.stream.Collectors;
 import org.objectweb.asm.*;
 import org.objectweb.asm.signature.SignatureReader;
 
@@ -27,6 +28,9 @@ public List<ClassDecl> getVisited() {
   List<ClassDecl> visited = new ArrayList<>();
   Stack<ClassDecl> visiting = new Stack<>();
 
+  /// Actual access for the inner classes as originally defined.
+  Map<String, Integer> actualAccess = new HashMap<>();
+
   public AsmClassVisitor() {
     super(AsmConstants.API);
   }
@@ -42,9 +46,8 @@ public void visit(
     var current = new ClassDecl();
     visiting.push(current);
     var type = Type.getObjectType(name);
-    current.binaryName = type.getClassName();
-    current.modifiers = TypeUtils.access(access);
-    current.parentName = TypeUtils.parentName(type);
+    current.binaryName = name.replace('/', '.');
+    current.modifiers = TypeUtils.access(actualAccess.getOrDefault(current.binaryName, access));
     current.declKind = TypeUtils.declKind(access);
     current.superclass = TypeUtils.typeUsage(Type.getObjectType(superName), null);
     current.interfaces =
@@ -56,6 +59,21 @@ public void visit(
     super.visit(version, access, name, signature, superName, interfaces);
   }
 
+  @Override
+  public void visitInnerClass(String name, String outerName, String innerName, int access) {
+    var binaryName = name.replace('/', '.');
+    actualAccess.put(binaryName, access);
+    var alreadyVisitedInnerClass =
+        visited.stream()
+            .filter(decl -> decl.binaryName.equals(binaryName))
+            .collect(Collectors.toList());
+    // If the order of visit is outer first inner second.
+    // We still want to correct the modifiers.
+    if (!alreadyVisitedInnerClass.isEmpty()) {
+      alreadyVisitedInnerClass.get(0).modifiers = TypeUtils.access(access);
+    }
+  }
+
   @Override
   public FieldVisitor visitField(
       int access, String name, String descriptor, String signature, Object value) {
diff --git a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmMethodSignatureVisitor.java b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmMethodSignatureVisitor.java
index 9067f9eb9..5410acfa1 100644
--- a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmMethodSignatureVisitor.java
+++ b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmMethodSignatureVisitor.java
@@ -7,11 +7,13 @@
 import com.github.dart_lang.jnigen.apisummarizer.elements.Method;
 import com.github.dart_lang.jnigen.apisummarizer.elements.TypeParam;
 import com.github.dart_lang.jnigen.apisummarizer.elements.TypeUsage;
+import java.util.ArrayList;
+import java.util.List;
 import org.objectweb.asm.signature.SignatureVisitor;
 
 public class AsmMethodSignatureVisitor extends SignatureVisitor {
   private final Method method;
-  private int paramIndex = -1;
+  private final List<TypeUsage> paramTypes = new ArrayList<>();
 
   public AsmMethodSignatureVisitor(Method method) {
     super(AsmConstants.API);
@@ -43,13 +45,22 @@ public SignatureVisitor visitInterfaceBound() {
 
   @Override
   public SignatureVisitor visitReturnType() {
+    // Visiting params finished.
+    //
+    // In case of non-static inner class constructor, there is an extra parent parameter
+    // at the beginning which is not accounted for by the signature. So we fill the types
+    // for the last [paramTypes.size()] params.
+    int startIndex = method.params.size() - paramTypes.size();
+    for (int i = 0; i < paramTypes.size(); ++i) {
+      method.params.get(startIndex + i).type = paramTypes.get(i);
+    }
     return new AsmTypeUsageSignatureVisitor(method.returnType);
   }
 
   @Override
   public SignatureVisitor visitParameterType() {
-    paramIndex++;
-    return new AsmTypeUsageSignatureVisitor(method.params.get(paramIndex).type);
+    paramTypes.add(new TypeUsage());
+    return new AsmTypeUsageSignatureVisitor(paramTypes.get(paramTypes.size() - 1));
   }
 
   @Override
diff --git a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmSummarizer.java b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmSummarizer.java
index 391b83160..485c44268 100644
--- a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmSummarizer.java
+++ b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmSummarizer.java
@@ -8,22 +8,19 @@
 
 import com.github.dart_lang.jnigen.apisummarizer.elements.ClassDecl;
 import com.github.dart_lang.jnigen.apisummarizer.util.InputStreamProvider;
-import java.util.ArrayList;
 import java.util.List;
 import org.objectweb.asm.ClassReader;
 
 public class AsmSummarizer {
 
   public static List<ClassDecl> run(List<InputStreamProvider> inputProviders) {
-    List<ClassDecl> parsed = new ArrayList<>();
+    var visitor = new AsmClassVisitor();
     for (var provider : inputProviders) {
       var inputStream = provider.getInputStream();
       var classReader = wrapCheckedException(ClassReader::new, inputStream);
-      var visitor = new AsmClassVisitor();
       classReader.accept(visitor, 0);
-      parsed.addAll(visitor.getVisited());
       provider.close();
     }
-    return parsed;
+    return visitor.getVisited();
   }
 }
diff --git a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmTypeUsageSignatureVisitor.java b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmTypeUsageSignatureVisitor.java
index 3c52c1045..6ddda4546 100644
--- a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmTypeUsageSignatureVisitor.java
+++ b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/AsmTypeUsageSignatureVisitor.java
@@ -93,7 +93,8 @@ public SignatureVisitor visitTypeArgument(char wildcard) {
 
   @Override
   public void visitInnerClassType(String name) {
-    super.visitInnerClassType(name);
-    // TODO(#139) support nested generic classes
+    typeUsage.shorthand += "." + name;
+    ((TypeUsage.DeclaredType) typeUsage.type).binaryName += "$" + name;
+    ((TypeUsage.DeclaredType) typeUsage.type).simpleName = name;
   }
 }
diff --git a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/TypeUtils.java b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/TypeUtils.java
index 521c02d52..8f1856523 100644
--- a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/TypeUtils.java
+++ b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/disasm/TypeUtils.java
@@ -19,14 +19,6 @@
 
 class TypeUtils {
 
-  public static String parentName(Type type) {
-    var className = type.getClassName();
-    if (!className.contains("$")) {
-      return null;
-    }
-    return className.split("\\$")[0];
-  }
-
   public static String simpleName(Type type) {
     var internalName = type.getInternalName();
     if (type.getInternalName().length() == 1) {
@@ -46,7 +38,8 @@ public static TypeUsage typeUsage(Type type, @SuppressWarnings("unused") String
       case OBJECT:
         usage.kind = TypeUsage.Kind.DECLARED;
         usage.type =
-            new TypeUsage.DeclaredType(type.getClassName(), TypeUtils.simpleName(type), null);
+            new TypeUsage.DeclaredType(
+                type.getInternalName().replace('/', '.'), TypeUtils.simpleName(type), null);
         break;
       case ARRAY:
         usage.kind = TypeUsage.Kind.ARRAY;
diff --git a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/doclet/ElementBuilders.java b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/doclet/ElementBuilders.java
index d0f2301c5..7ca8bb62e 100644
--- a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/doclet/ElementBuilders.java
+++ b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/doclet/ElementBuilders.java
@@ -40,10 +40,6 @@ private void fillInFromTypeElement(TypeElement e, ClassDecl c) {
         throw new RuntimeException(
             "Unexpected element kind " + e.getKind() + " on " + c.binaryName);
     }
-    var parent = e.getEnclosingElement();
-    if (parent instanceof TypeElement) {
-      c.parentName = env.elements.getBinaryName((TypeElement) parent).toString();
-    }
     c.javadoc = docComment(env.trees.getDocCommentTree(e));
     c.typeParams = StreamUtil.map(e.getTypeParameters(), this::typeParam);
     var superclass = e.getSuperclass();
diff --git a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/elements/ClassDecl.java b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/elements/ClassDecl.java
index 231f0f5b9..746b91378 100644
--- a/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/elements/ClassDecl.java
+++ b/pkgs/jnigen/java/src/main/java/com/github/dart_lang/jnigen/apisummarizer/elements/ClassDecl.java
@@ -27,7 +27,6 @@ public class ClassDecl {
    */
   public String binaryName;
 
-  public String parentName;
   public List<TypeParam> typeParams = new ArrayList<>();
   public List<Method> methods = new ArrayList<>();
   public List<Field> fields = new ArrayList<>();
diff --git a/pkgs/jnigen/lib/src/bindings/c_generator.dart b/pkgs/jnigen/lib/src/bindings/c_generator.dart
index dedef7666..79b07c8b6 100644
--- a/pkgs/jnigen/lib/src/bindings/c_generator.dart
+++ b/pkgs/jnigen/lib/src/bindings/c_generator.dart
@@ -11,72 +11,6 @@ import '../util/find_package.dart';
 import '../util/string_util.dart';
 import 'visitor.dart';
 
-/// JVM representation of type signatures.
-///
-/// https://docs.oracle.com/en/java/javase/18/docs/specs/jni/types.html#type-signatures
-class Descriptor extends TypeVisitor<String> {
-  const Descriptor();
-
-  @override
-  String visitArrayType(ArrayType node) {
-    final inner = node.type.accept(this);
-    return '[$inner';
-  }
-
-  @override
-  String visitDeclaredType(DeclaredType node) {
-    final internalName = node.binaryName.replaceAll('.', '/');
-    return 'L$internalName;';
-  }
-
-  @override
-  String visitPrimitiveType(PrimitiveType node) {
-    return node.signature;
-  }
-
-  @override
-  String visitTypeVar(TypeVar node) {
-    // It should be possible to compute the erasure of a type
-    // in parser itself.
-    // TODO(#23): Use erasure of the type variable here.
-    // This is just a (wrong) placeholder
-    return super.visitTypeVar(node);
-  }
-
-  @override
-  String visitWildcard(Wildcard node) {
-    final extendsBound = node.extendsBound?.accept(this);
-    return extendsBound ?? 'Ljava/lang/Object;';
-  }
-
-  @override
-  String visitNonPrimitiveType(ReferredType node) {
-    return "Ljava/lang/Object;";
-  }
-}
-
-/// Generates JNI Method signatures.
-///
-/// https://docs.oracle.com/en/java/javase/18/docs/specs/jni/types.html#type-signatures
-/// Also see: [Descriptor]
-class MethodSignature extends Visitor<Method, String> {
-  const MethodSignature();
-
-  @override
-  String visit(Method node) {
-    final s = StringBuffer();
-    s.write('(');
-    s.write(node.params
-        .map((param) => param.type)
-        .accept(const Descriptor())
-        .join());
-    s.write(')');
-    final returnType = node.returnType.accept(const Descriptor());
-    s.write(returnType);
-    return s.toString();
-  }
-}
-
 class CFieldName extends Visitor<Field, String> {
   const CFieldName();
 
@@ -255,7 +189,7 @@ class _CMethodGenerator extends Visitor<Method, void> {
       if (!node.isCtor && !node.isStatic) 'jobject self_',
       ...node.params.accept(const _CParamGenerator(addReturnType: true)),
     ].join(',');
-    final jniSignature = node.accept(const MethodSignature());
+    final jniSignature = node.descriptor;
     final ifStaticMethodID = node.isStatic ? 'static_' : '';
 
     var javaReturnType = node.returnType.type;
@@ -357,7 +291,7 @@ $cReturnType ${cMethodPrefix}_$fieldNameInC($formalArgs) {
     $_loadEnvCall
     ${node.classDecl.accept(_CLoadClassGenerator())}
     load_${ifStaticField}field($classVar, &$fieldVar, "$fieldName",
-      "${node.type.accept(const Descriptor())}");
+      "${node.type.descriptor}");
 $accessorStatements
 }
 
diff --git a/pkgs/jnigen/lib/src/bindings/dart_generator.dart b/pkgs/jnigen/lib/src/bindings/dart_generator.dart
index 2854e6be4..3db7c0bc7 100644
--- a/pkgs/jnigen/lib/src/bindings/dart_generator.dart
+++ b/pkgs/jnigen/lib/src/bindings/dart_generator.dart
@@ -7,6 +7,7 @@ import 'dart:io';
 import 'package:meta/meta.dart';
 
 import '../config/config.dart';
+import '../config/experiments.dart';
 import '../elements/elements.dart';
 import '../logging/logging.dart';
 import '../util/string_util.dart';
@@ -33,6 +34,7 @@ const _voidPointer = '$_ffi.Pointer<$_ffi.Void>';
 const _typeParamPrefix = '\$';
 
 // Misc.
+const _protectedExtension = 'ProtectedJniExtensions';
 const _classRef = '_class.reference';
 const _env = '$_jni.Jni.env';
 const _accessors = '$_jni.Jni.accessors';
@@ -128,7 +130,7 @@ class DartGenerator extends Visitor<Classes, Future<void>> {
 // Auto-generated initialization code.
 
 final $_ffi.Pointer<T> Function<T extends $_ffi.NativeType>(String sym) $_lookup =
-    ProtectedJniExtensions.initGeneratedLibrary("${config.outputConfig.cConfig!.libraryName}");
+    $_protectedExtension.initGeneratedLibrary("${config.outputConfig.cConfig!.libraryName}");
 
 
 ''';
@@ -155,6 +157,7 @@ import "package:jni/jni.dart" as jni;
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 ''';
@@ -399,6 +402,119 @@ class $name$typeParamsDef extends $superName {
       method.accept(methodGenerator);
     }
 
+    // Experimental: Interface implementation
+    if (node.declKind == DeclKind.interfaceKind &&
+        (config.experiments?.contains(Experiment.interfaceImplementation) ??
+            false)) {
+      s.write('''
+  /// Maps a specific port to the implemented methods.
+  static final Map<int, Map<String, Function>> _\$methods = {};
+
+  /// Maps a specific port to the type parameters.
+  static final Map<int, Map<String, $_jType>> _\$types = {};
+
+  ReceivePort? _\$p;
+
+  static final Finalizer<ReceivePort> _\$finalizer = Finalizer((\$p) {
+    _\$methods.remove(\$p.sendPort.nativePort);
+    _\$types.remove(\$p.sendPort.nativePort);
+    \$p.close();
+  });
+
+  @override
+  void delete() {
+    _\$methods.remove(_\$p?.sendPort.nativePort);
+    _\$types.remove(_\$p?.sendPort.nativePort);
+    _\$p?.close();
+    _\$finalizer.detach(this);
+    super.delete();
+  }
+
+  static jni.JObjectPtr _\$invoke(
+    int port,
+    jni.JObjectPtr descriptor,
+    jni.JObjectPtr args,
+  ) {
+    return _\$invokeMethod(
+      port,
+      \$MethodInvocation.fromAddresses(
+        0,
+        descriptor.address,
+        args.address,
+      ),
+    );
+  }
+
+  static final ffi.Pointer<
+          ffi.NativeFunction<
+              jni.JObjectPtr Function(
+                  ffi.Uint64, jni.JObjectPtr, jni.JObjectPtr)>>
+      _\$invokePointer = ffi.Pointer.fromFunction(_\$invoke);
+
+  static ffi.Pointer<ffi.Void> _\$invokeMethod(
+    int \$p,
+    \$MethodInvocation \$i,
+  ) {
+    final \$d = \$i.methodDescriptor.toDartString(deleteOriginal: true);
+    final \$a = \$i.args;
+    ''');
+      final proxyMethodIf = _InterfaceMethodIf(resolver, s);
+      for (final method in node.methods) {
+        method.accept(proxyMethodIf);
+      }
+      s.write('''
+    return jni.nullptr;
+  }
+
+  factory $name.implement(
+''');
+      final typeClassesCall =
+          typeParams.map((typeParam) => '$typeParam,').join(_newLine(depth: 3));
+      s.write(_encloseIfNotEmpty(
+        '{',
+        [
+          ...typeParams
+              .map((typeParam) => 'required $_jType<\$$typeParam> $typeParam,'),
+          ...node.methods.accept(_InterfaceImplementArg(resolver))
+        ].join(_newLine(depth: 2)),
+        '}',
+      ));
+
+      s.write('''
+      ) {
+    final \$p = ReceivePort();
+    final \$x = $name.fromRef(
+      $typeClassesCall
+      $_protectedExtension.newPortProxy(
+        r"${node.binaryName}",
+        \$p,
+        _\$invokePointer,
+      ),
+    ).._\$p = \$p;
+    final \$a = \$p.sendPort.nativePort; 
+    _\$types[\$a] = {};
+    _\$methods[\$a] = {};
+''');
+      final typeFiller = _InterfaceTypesFiller(s);
+      for (final typeParam in node.allTypeParams) {
+        typeParam.accept(typeFiller);
+      }
+      final methodFiller = _InterfaceMethodsFiller(s);
+      for (final method in node.methods) {
+        method.accept(methodFiller);
+      }
+      s.write('''
+    _\$finalizer.attach(\$x, \$p, detach: \$x);
+    \$p.listen((\$m) {
+      final \$i = \$MethodInvocation.fromMessage(\$m);
+      final \$r = _\$invokeMethod(\$p.sendPort.nativePort, \$i);
+      ProtectedJniExtensions.returnResult(\$i.result, \$r);
+    });
+    return \$x;
+  }
+  ''');
+    }
+
     // End of Class definition
     s.writeln('}');
 
@@ -491,7 +607,7 @@ class _TypeGenerator extends TypeVisitor<String> {
   String visitArrayType(ArrayType node) {
     final innerType = node.type;
     if (innerType.kind == Kind.primitive) {
-      return '$_jArray<$_jni.${(innerType.type as PrimitiveType).jniType}>';
+      return '$_jArray<$_jni.j${(innerType.type as PrimitiveType).name}>';
     }
     return '$_jArray<${innerType.accept(this)}>';
   }
@@ -565,14 +681,32 @@ class _TypeClass {
 /// Generates the type class.
 class _TypeClassGenerator extends TypeVisitor<_TypeClass> {
   final bool isConst;
+
+  /// Whether or not to return the equivalent boxed type class for primitives.
+  /// Only for interface implemetation.
+  final bool boxPrimitives;
+
+  /// Whether or not to find the correct type variable from the static map.
+  /// Only for interface implemetation.
+  final bool typeVarFromMap;
+
   final Resolver resolver;
 
-  _TypeClassGenerator(this.resolver, {this.isConst = true});
+  _TypeClassGenerator(
+    this.resolver, {
+    this.isConst = true,
+    this.boxPrimitives = false,
+    this.typeVarFromMap = false,
+  });
 
   @override
   _TypeClass visitArrayType(ArrayType node) {
-    final innerTypeClass =
-        node.type.accept(_TypeClassGenerator(resolver, isConst: false));
+    final innerTypeClass = node.type.accept(_TypeClassGenerator(
+      resolver,
+      isConst: false,
+      boxPrimitives: boxPrimitives,
+      typeVarFromMap: typeVarFromMap,
+    ));
     final ifConst = innerTypeClass.canBeConst && isConst ? 'const ' : '';
     return _TypeClass(
       '$ifConst${_jArray}Type(${innerTypeClass.name})',
@@ -587,8 +721,12 @@ class _TypeClassGenerator extends TypeVisitor<_TypeClass> {
         .toList();
 
     // The ones that are declared.
-    final definedTypeClasses =
-        node.params.accept(_TypeClassGenerator(resolver, isConst: false));
+    final definedTypeClasses = node.params.accept(_TypeClassGenerator(
+      resolver,
+      isConst: false,
+      boxPrimitives: boxPrimitives,
+      typeVarFromMap: typeVarFromMap,
+    ));
 
     // Can be const if all the type parameters are defined and each of them are
     // also const.
@@ -628,11 +766,15 @@ class _TypeClassGenerator extends TypeVisitor<_TypeClass> {
   @override
   _TypeClass visitPrimitiveType(PrimitiveType node) {
     final ifConst = isConst ? 'const ' : '';
-    return _TypeClass('$ifConst$_jni.${node.jniType}Type()', true);
+    final name = boxPrimitives ? 'J${node.boxedName}' : 'j${node.name}';
+    return _TypeClass('$ifConst$_jni.${name}Type()', true);
   }
 
   @override
   _TypeClass visitTypeVar(TypeVar node) {
+    if (typeVarFromMap) {
+      return _TypeClass('_\$types[\$p]!["${node.name}"]!', false);
+    }
     return _TypeClass(node.name, false);
   }
 
@@ -823,7 +965,7 @@ class _FieldGenerator extends Visitor<Field, void> {
   void writeDartOnlyAccessor(Field node) {
     final name = node.finalName;
     final ifStatic = node.isStatic ? 'Static' : '';
-    final descriptor = node.type.accept(const Descriptor());
+    final descriptor = node.type.descriptor;
     s.write('''
   static final _id_$name = 
       $_accessors.get${ifStatic}FieldIDOf(
@@ -950,10 +1092,10 @@ class _MethodGenerator extends Visitor<Method, void> {
   void writeDartOnlyAccessor(Method node) {
     final name = node.finalName;
     final ifStatic = node.isStatic ? 'Static' : '';
-    final signature = node.accept(const MethodSignature());
+    final descriptor = node.descriptor;
     s.write('''
   static final _id_$name = $_accessors.get${ifStatic}MethodIDOf(
-          $_classRef, r"${node.name}", r"$signature");
+          $_classRef, r"${node.name}", r"$descriptor");
 
 ''');
   }
@@ -1110,7 +1252,7 @@ class _MethodGenerator extends Visitor<Method, void> {
       s.write('''async {
     $typeInference
     final \$p = ReceivePort();
-    final \$c = $_jObject.fromRef($_jni.Jni.newPortContinuation(\$p));
+    final \$c = $_jObject.fromRef($_protectedExtension.newPortContinuation(\$p));
     $callExpr;
     final \$o = $_jPointer.fromAddress(await \$p.first);
     final \$k = $returnTypeClass.getClass().reference;
@@ -1367,3 +1509,129 @@ class _TypeVarLocator extends TypeVisitor<Map<String, List<OutsideInBuffer>>> {
     return {};
   }
 }
+
+/// The argument for .implement method of interfaces.
+class _InterfaceImplementArg extends Visitor<Method, String> {
+  final Resolver resolver;
+
+  _InterfaceImplementArg(this.resolver);
+
+  @override
+  String visit(Method node) {
+    final returnType = node.returnType.accept(_TypeGenerator(resolver));
+    final name = node.finalName;
+    final args = node.params.accept(_ParamDef(resolver)).join(', ');
+    return 'required $returnType Function($args) $name,';
+  }
+}
+
+/// The if statement to check which method has been called from the proxy class.
+class _InterfaceMethodIf extends Visitor<Method, void> {
+  final Resolver resolver;
+  final StringSink s;
+
+  _InterfaceMethodIf(this.resolver, this.s);
+
+  @override
+  void visit(Method node) {
+    final signature = node.javaSig;
+    final saveResult = node.returnType.name == 'void' ? '' : 'final \$r = ';
+    s.write('''
+      if (\$d == r"$signature") {
+        ${saveResult}_\$methods[\$p]![\$d]!(
+''');
+    for (var i = 0; i < node.params.length; ++i) {
+      node.params[i].accept(_InterfaceParamCast(resolver, s, paramIndex: i));
+    }
+    const returnBox = _InterfaceReturnBox();
+    s.write('''
+        );
+        return ${node.returnType.accept(returnBox)};
+      }
+''');
+  }
+}
+
+/// Generates casting to the correct parameter type from the list of JObject
+/// arguments received from the call to the proxy class.
+class _InterfaceParamCast extends Visitor<Param, void> {
+  final Resolver resolver;
+  final StringSink s;
+  final int paramIndex;
+
+  _InterfaceParamCast(
+    this.resolver,
+    this.s, {
+    required this.paramIndex,
+  });
+
+  @override
+  void visit(Param node) {
+    final typeClass = node.type
+        .accept(_TypeClassGenerator(
+          resolver,
+          boxPrimitives: true,
+          typeVarFromMap: true,
+        ))
+        .name;
+    s.write('\$a[$paramIndex].castTo($typeClass, deleteOriginal: true)');
+    if (node.type.kind == Kind.primitive) {
+      // Convert to Dart type.
+      final name = (node.type.type as PrimitiveType).name;
+      s.write('.${name}Value(deleteOriginal: true)');
+    }
+    s.writeln(',');
+  }
+}
+
+/// Boxes the returned primitive value into the correct Boxed type.
+/// Only returns the reference for non primitive types.
+/// Returns null for void.
+///
+/// For example `$r.toJInteger().reference` when the return type is `integer`.
+class _InterfaceReturnBox extends TypeVisitor<String> {
+  const _InterfaceReturnBox();
+
+  @override
+  String visitNonPrimitiveType(ReferredType node) {
+    return '\$r.reference';
+  }
+
+  @override
+  String visitPrimitiveType(PrimitiveType node) {
+    if (node.name == 'void') {
+      return '$_jni.nullptr';
+    }
+    return '$_jni.J${node.boxedName}(\$r).reference';
+  }
+}
+
+/// Fills the static _$types map with the correct type classes for the given
+/// port.
+class _InterfaceTypesFiller extends Visitor<TypeParam, void> {
+  final StringSink s;
+
+  _InterfaceTypesFiller(this.s);
+
+  @override
+  void visit(TypeParam node) {
+    s.write('''
+    _\$types[\$a]!["${node.name}"] = ${node.name};
+''');
+  }
+}
+
+/// Fills the static _$method map with the correct callbacks for the given
+/// port.
+class _InterfaceMethodsFiller extends Visitor<Method, void> {
+  final StringSink s;
+
+  _InterfaceMethodsFiller(this.s);
+
+  @override
+  void visit(Method node) {
+    s.write('''
+    _\$methods[\$a]![r"${node.javaSig}"] = ${node.finalName};
+''');
+  }
+}
diff --git a/pkgs/jnigen/lib/src/bindings/descriptor.dart b/pkgs/jnigen/lib/src/bindings/descriptor.dart
new file mode 100644
index 000000000..f7d774ae0
--- /dev/null
+++ b/pkgs/jnigen/lib/src/bindings/descriptor.dart
@@ -0,0 +1,115 @@
+import '../elements/elements.dart';
+import 'visitor.dart';
+
+/// Adds the type and method descriptor to all methods in all of the classes.
+///
+/// ASM already fills the descriptor field for methods but doclet does not.
+class Descriptor extends Visitor<Classes, void> {
+  const Descriptor();
+
+  @override
+  void visit(Classes node) {
+    for (final classDecl in node.decls.values) {
+      classDecl.accept(const _ClassDescriptor());
+    }
+  }
+}
+
+class _ClassDescriptor extends Visitor<ClassDecl, void> {
+  const _ClassDescriptor();
+
+  @override
+  void visit(ClassDecl node) {
+    final methodDescriptor = MethodDescriptor(node.allTypeParams);
+    for (final method in node.methods) {
+      method.descriptor ??= method.accept(methodDescriptor);
+    }
+    final typeDescriptor = TypeDescriptor(node.allTypeParams);
+    for (final field in node.fields) {
+      field.type.descriptor = field.type.accept(typeDescriptor);
+    }
+    for (final interface in node.interfaces) {
+      interface.descriptor = interface.accept(typeDescriptor);
+    }
+  }
+}
+
+/// Generates JNI Method descriptor.
+///
+/// https://docs.oracle.com/en/java/javase/18/docs/specs/jni/types.html#type-signatures
+/// Also see: [TypeDescriptor]
+class MethodDescriptor extends Visitor<Method, String> {
+  final List<TypeParam> typeParams;
+
+  MethodDescriptor(this.typeParams);
+
+  @override
+  String visit(Method node) {
+    final s = StringBuffer();
+    final typeParamsIncludingThis = [...typeParams, ...node.typeParams];
+    final typeDescriptor = TypeDescriptor(typeParamsIncludingThis);
+    s.write('(');
+    for (final param in node.params) {
+      final desc = param.type.accept(typeDescriptor);
+      param.type.descriptor = desc;
+      s.write(desc);
+    }
+    s.write(')');
+    final returnTypeDesc =
+        node.returnType.accept(TypeDescriptor(typeParamsIncludingThis));
+    node.returnType.descriptor = returnTypeDesc;
+    s.write(returnTypeDesc);
+    return s.toString();
+  }
+}
+
+/// JVM representation of type signatures.
+///
+/// https://docs.oracle.com/en/java/javase/18/docs/specs/jni/types.html#type-signatures
+class TypeDescriptor extends TypeVisitor<String> {
+  final List<TypeParam> typeParams;
+
+  TypeDescriptor(this.typeParams);
+
+  @override
+  String visitArrayType(ArrayType node) {
+    final inner = node.type.accept(this);
+    return '[$inner';
+  }
+
+  @override
+  String visitDeclaredType(DeclaredType node) {
+    final internalName = node.binaryName.replaceAll('.', '/');
+    return 'L$internalName;';
+  }
+
+  @override
+  String visitPrimitiveType(PrimitiveType node) {
+    return node.signature;
+  }
+
+  @override
+  String visitTypeVar(TypeVar node) {
+    final typeParam = typeParams.lastWhere(
+      (typeParam) => typeParam.name == node.name,
+      orElse: () {
+        print('${node.name} was not found!');
+        throw 'error';
+      },
+    );
+    return typeParam.bounds.isEmpty
+        ? super.visitTypeVar(node)
+        : typeParam.bounds.first.accept(this);
+  }
+
+  @override
+  String visitWildcard(Wildcard node) {
+    final extendsBound = node.extendsBound?.accept(this);
+    return extendsBound ?? super.visitWildcard(node);
+  }
+
+  @override
+  String visitNonPrimitiveType(ReferredType node) {
+    return 'Ljava/lang/Object;';
+  }
+}
diff --git a/pkgs/jnigen/lib/src/bindings/unnester.dart b/pkgs/jnigen/lib/src/bindings/unnester.dart
index 00522051a..d9323df91 100644
--- a/pkgs/jnigen/lib/src/bindings/unnester.dart
+++ b/pkgs/jnigen/lib/src/bindings/unnester.dart
@@ -10,6 +10,8 @@ import 'visitor.dart';
 /// Nested classes are not supported in Dart. So this "unnests" them into
 /// separate classes.
 class Unnester extends Visitor<Classes, void> {
+  const Unnester();
+
   @override
   void visit(node) {
     final classProcessor = _ClassUnnester();
@@ -53,9 +55,14 @@ class _MethodUnnester extends Visitor<Method, void> {
   void visit(Method node) {
     assert(!node.classDecl.isStatic);
     assert(node.classDecl.isNested);
-    if (node.isCtor || node.isStatic) {
+    // TODO(#319): Unnest the methods in APISummarizer itself.
+    // For now the nullity of [node.descriptor] identifies if the doclet
+    // backend was used and the method would potentially need "unnesting".
+    if ((node.isCtor || node.isStatic) && node.descriptor == null) {
       // Non-static nested classes take an instance of their outer class as the
-      // first parameter. This is not accounted for by the summarizer, so we
+      // first parameter.
+      //
+      // This is not accounted for by the **doclet** summarizer, so we
       // manually add it as the first parameter.
       final parentTypeParamCount = node.classDecl.allTypeParams.length -
           node.classDecl.typeParams.length;
diff --git a/pkgs/jnigen/lib/src/config/config_types.dart b/pkgs/jnigen/lib/src/config/config_types.dart
index c1d166bff..8004cee46 100644
--- a/pkgs/jnigen/lib/src/config/config_types.dart
+++ b/pkgs/jnigen/lib/src/config/config_types.dart
@@ -13,6 +13,7 @@ import '../elements/elements.dart';
 import '../logging/logging.dart';
 import '../util/find_package.dart';
 import 'config_exception.dart';
+import 'experiments.dart';
 import 'filters.dart';
 import 'yaml_reader.dart';
 
@@ -117,13 +118,39 @@ class AndroidSdkConfig {
   String? androidExample;
 }
 
+extension on String {
+  /// Converts the enum name from camelCase to snake_case.
+  String toSnakeCase() {
+    return splitMapJoin(
+      RegExp('[A-Z]'),
+      onMatch: (p) => '_${p[0]!.toLowerCase()}',
+    );
+  }
+}
+
+extension<T extends Enum> on Iterable<T> {
+  Map<String, T> valuesMap() {
+    return Map.fromEntries(map((e) => MapEntry(e.name.toSnakeCase(), e)));
+  }
+}
+
+T _getEnumValueFromString<T>(
+    Map<String, T> values, String? name, T defaultVal) {
+  if (name == null) return defaultVal;
+  final value = values[name];
+  if (value == null) {
+    throw ConfigException('Got: $name, allowed: ${values.keys}');
+  }
+  return value;
+}
+
 /// Additional options to pass to the summary generator component.
 class SummarizerOptions {
   SummarizerOptions(
       {this.extraArgs = const [], this.workingDirectory, this.backend});
   List<String> extraArgs;
   Uri? workingDirectory;
-  String? backend;
+  SummarizerBackend? backend;
 }
 
 /// Backend for reading summary of Java libraries
@@ -135,14 +162,15 @@ enum SummarizerBackend {
   doclet,
 }
 
-T _getEnumValueFromString<T>(
-    Map<String, T> values, String? name, T defaultVal) {
-  if (name == null) return defaultVal;
-  final value = values[name];
-  if (value == null) {
-    throw ConfigException('Got: $name, allowed: ${values.keys}');
-  }
-  return value;
+SummarizerBackend? getSummarizerBackend(
+  String? name,
+  SummarizerBackend? defaultVal,
+) {
+  return _getEnumValueFromString(
+    SummarizerBackend.values.valuesMap(),
+    name,
+    defaultVal,
+  );
 }
 
 void _ensureIsDirectory(String name, Uri path) {
@@ -155,31 +183,27 @@ void _ensureIsDirectory(String name, Uri path) {
 enum OutputStructure { packageStructure, singleFile }
 
 OutputStructure getOutputStructure(String? name, OutputStructure defaultVal) {
-  const values = {
-    'package_structure': OutputStructure.packageStructure,
-    'single_file': OutputStructure.singleFile,
-  };
-  return _getEnumValueFromString(values, name, defaultVal);
+  return _getEnumValueFromString(
+    OutputStructure.values.valuesMap(),
+    name,
+    defaultVal,
+  );
 }
 
 enum BindingsType { cBased, dartOnly }
 
 extension GetConfigString on BindingsType {
-  static const _configStrings = {
-    BindingsType.cBased: 'c_based',
-    BindingsType.dartOnly: 'dart_only',
-  };
   String getConfigString() {
-    return _configStrings[this]!;
+    return name.toSnakeCase();
   }
 }
 
 BindingsType getBindingsType(String? name, BindingsType defaultVal) {
-  const values = {
-    'c_based': BindingsType.cBased,
-    'dart_only': BindingsType.dartOnly,
-  };
-  return _getEnumValueFromString(values, name, defaultVal);
+  return _getEnumValueFromString(
+    BindingsType.values.valuesMap(),
+    name,
+    defaultVal,
+  );
 }
 
 class CCodeOutputConfig {
@@ -296,6 +320,7 @@ class Config {
   Config({
     required this.outputConfig,
     required this.classes,
+    this.experiments,
     this.exclude,
     this.sourcePath,
     this.classPath,
@@ -324,6 +349,8 @@ class Config {
   /// name suffix is `.class`.
   List<String> classes;
 
+  Set<Experiment?>? experiments;
+
   /// Methods and fields to be excluded from generated bindings.
   final BindingExclusions? exclude;
 
@@ -351,7 +378,7 @@ class Config {
   final MavenDownloads? mavenDownloads;
 
   /// Additional options for the summarizer component.
-  final SummarizerOptions? summarizerOptions;
+  SummarizerOptions? summarizerOptions;
 
   /// List of dependencies.
   final List<Uri>? imports;
@@ -415,6 +442,7 @@ class Config {
             );
           }
           final classDecl = ClassDecl(
+            declKind: DeclKind.classKind,
             binaryName: binaryName,
           )
             ..path = '$importPath/$filePath'
@@ -535,7 +563,7 @@ class Config {
       classes: must(prov.getStringList, [], _Props.classes),
       summarizerOptions: SummarizerOptions(
         extraArgs: prov.getStringList(_Props.summarizerArgs) ?? const [],
-        backend: prov.getString(_Props.backend),
+        backend: getSummarizerBackend(prov.getString(_Props.backend), null),
         workingDirectory: prov.getPath(_Props.summarizerWorkingDir),
       ),
       exclude: BindingExclusions(
@@ -568,6 +596,12 @@ class Config {
             : null,
       ),
       preamble: prov.getString(_Props.preamble),
+      experiments: prov
+          .getStringList(_Props.experiments)
+          ?.map(
+            (e) => Experiment.fromString(e),
+          )
+          .toSet(),
       imports: prov.getPathList(_Props.import),
       mavenDownloads: prov.hasValue(_Props.mavenDownloads)
           ? MavenDownloads(
@@ -632,6 +666,7 @@ class _Props {
   static const excludeMethods = '$exclude.methods';
   static const excludeFields = '$exclude.fields';
 
+  static const experiments = 'enable_experiment';
   static const import = 'import';
   static const outputConfig = 'output';
   static const bindingsType = '$outputConfig.bindings_type';
diff --git a/pkgs/jnigen/lib/src/config/experiments.dart b/pkgs/jnigen/lib/src/config/experiments.dart
new file mode 100644
index 000000000..d0eb39dd6
--- /dev/null
+++ b/pkgs/jnigen/lib/src/config/experiments.dart
@@ -0,0 +1,38 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class Experiment {
+  static const available = [
+    interfaceImplementation,
+  ];
+
+  static const interfaceImplementation = Experiment(
+    name: 'interface_implementation',
+    description: 'Enables generation of machinery for '
+        'implementing Java interfaces in Dart.',
+    isExpired: false,
+  );
+
+  final String name;
+  final String description;
+  final bool isExpired;
+
+  const Experiment({
+    required this.name,
+    required this.description,
+    required this.isExpired,
+  });
+
+  factory Experiment.fromString(String s) {
+    final search = available.where((element) => element.name == s);
+    if (search.isEmpty) {
+      throw 'The experiment $s is not available in this version.';
+    }
+    final result = search.single;
+    if (result.isExpired) {
+      throw 'The experiment $s can no longer be used in this version. ';
+    }
+    return result;
+  }
+}
diff --git a/pkgs/jnigen/lib/src/elements/elements.dart b/pkgs/jnigen/lib/src/elements/elements.dart
index ceaee017c..020f05dbf 100644
--- a/pkgs/jnigen/lib/src/elements/elements.dart
+++ b/pkgs/jnigen/lib/src/elements/elements.dart
@@ -57,9 +57,9 @@ class ClassDecl extends ClassMember implements Element<ClassDecl> {
   ClassDecl({
     this.annotations = const [],
     this.javadoc,
+    required this.declKind,
     this.modifiers = const {},
     required this.binaryName,
-    this.parentName,
     this.typeParams = const [],
     this.methods = const [],
     this.fields = const [],
@@ -77,8 +77,8 @@ class ClassDecl extends ClassMember implements Element<ClassDecl> {
   final List<Annotation> annotations;
   final KotlinClass? kotlinClass;
   final JavaDocComment? javadoc;
+  final DeclKind declKind;
   final String binaryName;
-  final String? parentName;
   List<TypeParam> typeParams;
   List<Method> methods;
   List<Field> fields;
@@ -171,7 +171,13 @@ class ClassDecl extends ClassMember implements Element<ClassDecl> {
 
   bool get isObject => superCount == 0;
 
-  bool get isNested => parentName != null;
+  @JsonKey(includeFromJson: false)
+  late final String? parentName = binaryName.contains(r'$')
+      ? binaryName.splitMapJoin(RegExp(r'\$[^$]+$'), onMatch: (_) => '')
+      : null;
+
+  @JsonKey(includeFromJson: false)
+  late final isNested = parentName != null;
 }
 
 @JsonEnum()
@@ -206,10 +212,14 @@ class TypeUsage {
   @JsonKey(name: "type")
   final Map<String, dynamic> typeJson;
 
-  /// Populated by in [TypeUsage.fromJson].
+  /// Populated by [TypeUsage.fromJson].
   @JsonKey(includeFromJson: false)
   late final ReferredType type;
 
+  /// Populated by [Descriptor].
+  @JsonKey(includeFromJson: false)
+  late String descriptor;
+
   String get name => type.name;
 
   // Since json_serializable doesn't directly support union types,
@@ -255,7 +265,7 @@ class PrimitiveType extends ReferredType {
       name: 'byte',
       signature: 'B',
       dartType: 'int',
-      jniType: 'jbyte',
+      boxedName: 'Byte',
       cType: 'int8_t',
       ffiType: 'Int8',
     ),
@@ -263,7 +273,7 @@ class PrimitiveType extends ReferredType {
       name: 'short',
       signature: 'S',
       dartType: 'int',
-      jniType: 'jshort',
+      boxedName: 'Short',
       cType: 'int16_t',
       ffiType: 'Int16',
     ),
@@ -271,7 +281,7 @@ class PrimitiveType extends ReferredType {
       name: 'char',
       signature: 'C',
       dartType: 'int',
-      jniType: 'jchar',
+      boxedName: 'Character',
       cType: 'uint16_t',
       ffiType: 'Uint16',
     ),
@@ -279,7 +289,7 @@ class PrimitiveType extends ReferredType {
       name: 'int',
       signature: 'I',
       dartType: 'int',
-      jniType: 'jint',
+      boxedName: 'Integer',
       cType: 'int32_t',
       ffiType: 'Int32',
     ),
@@ -287,7 +297,7 @@ class PrimitiveType extends ReferredType {
       name: 'long',
       signature: 'J',
       dartType: 'int',
-      jniType: 'jlong',
+      boxedName: 'Long',
       cType: 'int64_t',
       ffiType: 'Int64',
     ),
@@ -295,7 +305,7 @@ class PrimitiveType extends ReferredType {
       name: 'float',
       signature: 'F',
       dartType: 'double',
-      jniType: 'jfloat',
+      boxedName: 'Float',
       cType: 'float',
       ffiType: 'Float',
     ),
@@ -303,7 +313,7 @@ class PrimitiveType extends ReferredType {
       name: 'double',
       signature: 'D',
       dartType: 'double',
-      jniType: 'jdouble',
+      boxedName: 'Double',
       cType: 'double',
       ffiType: 'Double',
     ),
@@ -311,7 +321,7 @@ class PrimitiveType extends ReferredType {
       name: 'boolean',
       signature: 'Z',
       dartType: 'bool',
-      jniType: 'jboolean',
+      boxedName: 'Boolean',
       cType: 'uint8_t',
       ffiType: 'Uint8',
     ),
@@ -319,7 +329,7 @@ class PrimitiveType extends ReferredType {
       name: 'void',
       signature: 'V',
       dartType: 'void',
-      jniType: 'jvoid', // Never used
+      boxedName: 'Void', // Not used.
       cType: 'void',
       ffiType: 'Void',
     ),
@@ -329,7 +339,7 @@ class PrimitiveType extends ReferredType {
     required this.name,
     required this.signature,
     required this.dartType,
-    required this.jniType,
+    required this.boxedName,
     required this.cType,
     required this.ffiType,
   });
@@ -339,7 +349,7 @@ class PrimitiveType extends ReferredType {
 
   final String signature;
   final String dartType;
-  final String jniType;
+  final String boxedName;
   final String cType;
   final String ffiType;
 
@@ -466,7 +476,8 @@ class Method extends ClassMember implements Element<Method> {
   /// Can be used to match with [KotlinFunction]'s descriptor.
   ///
   /// Can create a unique signature in combination with [name].
-  final String? descriptor;
+  /// Populated either by the ASM backend or [Descriptor].
+  String? descriptor;
 
   /// The [ClassDecl] where this method is defined.
   ///
@@ -489,12 +500,7 @@ class Method extends ClassMember implements Element<Method> {
   TypeUsage? asyncReturnType;
 
   @JsonKey(includeFromJson: false)
-  late String javaSig = _javaSig();
-
-  String _javaSig() {
-    final paramNames = params.map((p) => p.type.name).join(', ');
-    return '${returnType.name} $name($paramNames)';
-  }
+  late final String javaSig = '$name$descriptor';
 
   bool get isCtor => name == '<init>';
 
diff --git a/pkgs/jnigen/lib/src/elements/elements.g.dart b/pkgs/jnigen/lib/src/elements/elements.g.dart
index 4531342ec..dcd35dd38 100644
--- a/pkgs/jnigen/lib/src/elements/elements.g.dart
+++ b/pkgs/jnigen/lib/src/elements/elements.g.dart
@@ -14,12 +14,12 @@ ClassDecl _$ClassDeclFromJson(Map<String, dynamic> json) => ClassDecl(
       javadoc: json['javadoc'] == null
           ? null
           : JavaDocComment.fromJson(json['javadoc'] as Map<String, dynamic>),
+      declKind: $enumDecode(_$DeclKindEnumMap, json['declKind']),
       modifiers: (json['modifiers'] as List<dynamic>?)
               ?.map((e) => e as String)
               .toSet() ??
           const {},
       binaryName: json['binaryName'] as String,
-      parentName: json['parentName'] as String?,
       typeParams: (json['typeParams'] as List<dynamic>?)
               ?.map((e) => TypeParam.fromJson(e as Map<String, dynamic>))
               .toList() ??
@@ -48,6 +48,12 @@ ClassDecl _$ClassDeclFromJson(Map<String, dynamic> json) => ClassDecl(
           : KotlinClass.fromJson(json['kotlinClass'] as Map<String, dynamic>),
     );
 
+const _$DeclKindEnumMap = {
+  DeclKind.classKind: 'CLASS',
+  DeclKind.interfaceKind: 'INTERFACE',
+  DeclKind.enumKind: 'ENUM',
+};
+
 TypeUsage _$TypeUsageFromJson(Map<String, dynamic> json) => TypeUsage(
       shorthand: json['shorthand'] as String,
       kind: $enumDecode(_$KindEnumMap, json['kind']),
diff --git a/pkgs/jnigen/lib/src/generate_bindings.dart b/pkgs/jnigen/lib/src/generate_bindings.dart
index 174828eb3..883ca8575 100644
--- a/pkgs/jnigen/lib/src/generate_bindings.dart
+++ b/pkgs/jnigen/lib/src/generate_bindings.dart
@@ -7,6 +7,7 @@ import 'dart:convert';
 
 import 'bindings/c_generator.dart';
 import 'bindings/dart_generator.dart';
+import 'bindings/descriptor.dart';
 import 'bindings/excluder.dart';
 import 'bindings/kotlin_processor.dart';
 import 'bindings/linker.dart';
@@ -39,7 +40,8 @@ Future<void> generateJniBindings(Config config) async {
   classes.accept(Excluder(config));
   classes.accept(KotlinProcessor());
   await classes.accept(Linker(config));
-  classes.accept(Unnester());
+  classes.accept(const Unnester());
+  classes.accept(const Descriptor());
   classes.accept(Renamer(config));
 
   final cBased = config.outputConfig.bindingsType == BindingsType.cBased;
diff --git a/pkgs/jnigen/lib/src/summary/summary.dart b/pkgs/jnigen/lib/src/summary/summary.dart
index 09c13f5c8..170627582 100644
--- a/pkgs/jnigen/lib/src/summary/summary.dart
+++ b/pkgs/jnigen/lib/src/summary/summary.dart
@@ -44,11 +44,7 @@ class SummarizerCommand {
     this.workingDirectory,
     this.backend,
   })  : sourcePaths = sourcePath ?? [],
-        classPaths = classPath ?? [] {
-    if (backend != null && !{'asm', 'doclet'}.contains(backend)) {
-      throw ArgumentError('Supported backends: asm, doclet');
-    }
-  }
+        classPaths = classPath ?? [];
 
   static const sourcePathsOption = '-s';
   static const classPathsOption = '-c';
@@ -60,7 +56,7 @@ class SummarizerCommand {
   List<String> classes;
 
   Uri? workingDirectory;
-  String? backend;
+  SummarizerBackend? backend;
 
   void addSourcePaths(List<Uri> paths) {
     sourcePaths.addAll(paths);
@@ -91,7 +87,7 @@ class SummarizerCommand {
     _addPathParam(args, sourcePathsOption, sourcePaths);
     _addPathParam(args, classPathsOption, classPaths);
     if (backend != null) {
-      args.addAll(['--backend', backend!]);
+      args.addAll(['--backend', backend!.name]);
     }
     args.addAll(extraArgs);
     args.addAll(classes);
diff --git a/pkgs/jnigen/pubspec.yaml b/pkgs/jnigen/pubspec.yaml
index ee7043086..07be3c818 100644
--- a/pkgs/jnigen/pubspec.yaml
+++ b/pkgs/jnigen/pubspec.yaml
@@ -3,7 +3,7 @@
 # BSD-style license that can be found in the LICENSE file.
 
 name: jnigen
-version: 0.6.0-dev.1
+version: 0.6.0-wip.2
 description: Experimental generator for FFI+JNI bindings.
 repository: https://github.com/dart-lang/jnigen/tree/main/jnigen
 
diff --git a/pkgs/jnigen/test/config_test.dart b/pkgs/jnigen/test/config_test.dart
index 4b6617b35..ae2f9871e 100644
--- a/pkgs/jnigen/test/config_test.dart
+++ b/pkgs/jnigen/test/config_test.dart
@@ -35,6 +35,7 @@ void expectConfigsAreEqual(Config a, Config b) {
       equals(b.outputConfig.symbolsConfig?.path),
       reason: "symbolsRoot");
   expect(a.sourcePath, equals(b.sourcePath), reason: "sourcePath");
+  expect(a.experiments, equals(b.experiments), reason: "experiments");
   expect(a.classPath, equals(b.classPath), reason: "classPath");
   expect(a.preamble, equals(b.preamble), reason: "preamble");
   final am = a.mavenDownloads;
diff --git a/pkgs/jnigen/test/descriptor_test.dart b/pkgs/jnigen/test/descriptor_test.dart
new file mode 100644
index 000000000..41ac58cf5
--- /dev/null
+++ b/pkgs/jnigen/test/descriptor_test.dart
@@ -0,0 +1,43 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:jnigen/src/bindings/descriptor.dart';
+import 'package:jnigen/src/bindings/linker.dart';
+import 'package:jnigen/src/bindings/unnester.dart';
+import 'package:jnigen/src/config/config_types.dart';
+import 'package:jnigen/src/summary/summary.dart';
+import 'package:test/test.dart';
+
+import 'simple_package_test/generate.dart' as simple_package_test;
+import 'kotlin_test/generate.dart' as kotlin_test;
+import 'jackson_core_test/generate.dart' as jackson_core_test;
+import 'test_util/test_util.dart';
+
+void main() {
+  checkLocallyBuiltDependencies();
+  test('Method descriptor generation', timeout: const Timeout.factor(3),
+      () async {
+    final configGetters = [
+      simple_package_test.getConfig,
+      kotlin_test.getConfig,
+      jackson_core_test.getConfig
+    ];
+    for (final getConfig in configGetters) {
+      final config = getConfig();
+      config.summarizerOptions =
+          SummarizerOptions(backend: SummarizerBackend.asm);
+      final classes = await getSummary(config);
+      await classes.accept(Linker(config));
+      classes.accept(const Unnester());
+      for (final decl in classes.decls.values) {
+        // Checking if the descriptor from ASM matches the one generated by
+        // [MethodDescriptor].
+        final methodDescriptor = MethodDescriptor(decl.allTypeParams);
+        for (final method in decl.methods) {
+          expect(method.descriptor, method.accept(methodDescriptor));
+        }
+      }
+    }
+  });
+}
diff --git a/pkgs/jnigen/test/jackson_core_test/generate.dart b/pkgs/jnigen/test/jackson_core_test/generate.dart
index 7077bfa7e..796a760ca 100644
--- a/pkgs/jnigen/test/jackson_core_test/generate.dart
+++ b/pkgs/jnigen/test/jackson_core_test/generate.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:jnigen/jnigen.dart';
+import 'package:jnigen/src/config/experiments.dart';
 import 'package:logging/logging.dart';
 import 'package:path/path.dart' hide equals;
 
@@ -43,7 +44,7 @@ Config getConfig({
       jarDir: join(thirdPartyDir, 'jar'),
     ),
     summarizerOptions: SummarizerOptions(
-      backend: useAsm ? 'asm' : null,
+      backend: useAsm ? SummarizerBackend.asm : null,
     ),
     preamble: jacksonPreamble,
     outputConfig: OutputConfig(
@@ -69,17 +70,19 @@ Config getConfig({
           ],
     logLevel: Level.INFO,
     exclude: BindingExclusions(
-        // TODO(#31): Remove field exclusions.
-        fields: excludeAll<Field>([
-          ['com.fasterxml.jackson.core.JsonFactory', 'DEFAULT_QUOTE_CHAR'],
-          ['com.fasterxml.jackson.core.Base64Variant', 'PADDING_CHAR_NONE'],
-          ['com.fasterxml.jackson.core.base.ParserMinimalBase', 'CHAR_NULL'],
-          ['com.fasterxml.jackson.core.io.UTF32Reader', 'NC'],
-        ]),
-        // TODO(#159): Remove class exclusions.
-        classes: ClassNameFilter.exclude(
-          'com.fasterxml.jackson.core.JsonFactoryBuilder',
-        )),
+      // TODO(#31): Remove field exclusions.
+      fields: excludeAll<Field>([
+        ['com.fasterxml.jackson.core.JsonFactory', 'DEFAULT_QUOTE_CHAR'],
+        ['com.fasterxml.jackson.core.Base64Variant', 'PADDING_CHAR_NONE'],
+        ['com.fasterxml.jackson.core.base.ParserMinimalBase', 'CHAR_NULL'],
+        ['com.fasterxml.jackson.core.io.UTF32Reader', 'NC'],
+      ]),
+      // TODO(#159): Remove class exclusions.
+      classes: ClassNameFilter.exclude(
+        'com.fasterxml.jackson.core.JsonFactoryBuilder',
+      ),
+    ),
+    experiments: {Experiment.interfaceImplementation},
   );
   return config;
 }
diff --git a/pkgs/jnigen/test/jackson_core_test/jnigen.yaml b/pkgs/jnigen/test/jackson_core_test/jnigen.yaml
index 6041671c9..cf3b4db15 100644
--- a/pkgs/jnigen/test/jackson_core_test/jnigen.yaml
+++ b/pkgs/jnigen/test/jackson_core_test/jnigen.yaml
@@ -43,3 +43,6 @@ preamble: |
   // limitations under the License.
 
 log_level: warning
+
+enable_experiment:
+  - interface_implementation
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/dartjni.h b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/dartjni.h
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/jackson_core.c b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/jackson_core.c
index 74bf137c2..0f6b727df 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/jackson_core.c
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/c_bindings/jackson_core.c
@@ -3383,7 +3383,7 @@ JniResult JsonParser__readValueAsTree(jobject self_) {
   if (_c_JsonParser == NULL)
     return (JniResult){.value = {.j = 0}, .exception = check_exception()};
   load_method(_c_JsonParser, &_m_JsonParser__readValueAsTree, "readValueAsTree",
-              "()Ljava/lang/Object;");
+              "()Lcom/fasterxml/jackson/core/TreeNode;");
   if (_m_JsonParser__readValueAsTree == NULL)
     return (JniResult){.value = {.j = 0}, .exception = check_exception()};
   jobject _result = (*jniEnv)->CallObjectMethod(jniEnv, self_,
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart
index 0b91b29f0..33f513996 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart
@@ -29,6 +29,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart
index 1c60902d0..032db3141 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart
@@ -29,6 +29,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart
index fe8cf885d..14ce836aa 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/c_based/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart
@@ -29,6 +29,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart b/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart
index c58fb97aa..71a79f1b8 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonFactory.dart
@@ -29,6 +29,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart b/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart
index 601b40422..f978756ba 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonParser.dart
@@ -29,6 +29,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
@@ -2463,7 +2464,9 @@ class JsonParser extends jni.JObject {
   }
 
   static final _id_readValueAsTree = jni.Jni.accessors.getMethodIDOf(
-      _class.reference, r"readValueAsTree", r"()Ljava/lang/Object;");
+      _class.reference,
+      r"readValueAsTree",
+      r"()Lcom/fasterxml/jackson/core/TreeNode;");
 
   /// from: public T readValueAsTree()
   /// The returned object must be deleted after use, by calling the `delete` method.
diff --git a/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart b/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart
index b6bc6e549..aac454b68 100644
--- a/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart
+++ b/pkgs/jnigen/test/jackson_core_test/third_party/dart_only/dart_bindings/com/fasterxml/jackson/core/JsonToken.dart
@@ -29,6 +29,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
diff --git a/pkgs/jnigen/test/kotlin_test/c_based/c_bindings/dartjni.h b/pkgs/jnigen/test/kotlin_test/c_based/c_bindings/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jnigen/test/kotlin_test/c_based/c_bindings/dartjni.h
+++ b/pkgs/jnigen/test/kotlin_test/c_based/c_bindings/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jnigen/test/kotlin_test/c_based/dart_bindings/kotlin.dart b/pkgs/jnigen/test/kotlin_test/c_based/dart_bindings/kotlin.dart
index b8e33c26f..3e65d3b09 100644
--- a/pkgs/jnigen/test/kotlin_test/c_based/dart_bindings/kotlin.dart
+++ b/pkgs/jnigen/test/kotlin_test/c_based/dart_bindings/kotlin.dart
@@ -16,6 +16,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
@@ -61,7 +62,8 @@ class SuspendFun extends jni.JObject {
   /// The returned object must be deleted after use, by calling the `delete` method.
   Future<jni.JString> sayHello() async {
     final $p = ReceivePort();
-    final $c = jni.JObject.fromRef(jni.Jni.newPortContinuation($p));
+    final $c =
+        jni.JObject.fromRef(ProtectedJniExtensions.newPortContinuation($p));
     _sayHello(reference, $c.reference).object;
     final $o = jni.JObjectPtr.fromAddress(await $p.first);
     final $k = const jni.JStringType().getClass().reference;
@@ -87,7 +89,8 @@ class SuspendFun extends jni.JObject {
     jni.JString string,
   ) async {
     final $p = ReceivePort();
-    final $c = jni.JObject.fromRef(jni.Jni.newPortContinuation($p));
+    final $c =
+        jni.JObject.fromRef(ProtectedJniExtensions.newPortContinuation($p));
     _sayHello1(reference, string.reference, $c.reference).object;
     final $o = jni.JObjectPtr.fromAddress(await $p.first);
     final $k = const jni.JStringType().getClass().reference;
diff --git a/pkgs/jnigen/test/kotlin_test/dart_only/dart_bindings/kotlin.dart b/pkgs/jnigen/test/kotlin_test/dart_only/dart_bindings/kotlin.dart
index a0510088b..e4ceec3e6 100644
--- a/pkgs/jnigen/test/kotlin_test/dart_only/dart_bindings/kotlin.dart
+++ b/pkgs/jnigen/test/kotlin_test/dart_only/dart_bindings/kotlin.dart
@@ -16,6 +16,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
@@ -54,7 +55,8 @@ class SuspendFun extends jni.JObject {
   /// The returned object must be deleted after use, by calling the `delete` method.
   Future<jni.JString> sayHello() async {
     final $p = ReceivePort();
-    final $c = jni.JObject.fromRef(jni.Jni.newPortContinuation($p));
+    final $c =
+        jni.JObject.fromRef(ProtectedJniExtensions.newPortContinuation($p));
     jni.Jni.accessors.callMethodWithArgs(reference, _id_sayHello,
         jni.JniCallType.objectType, [$c.reference]).object;
     final $o = jni.JObjectPtr.fromAddress(await $p.first);
@@ -76,7 +78,8 @@ class SuspendFun extends jni.JObject {
     jni.JString string,
   ) async {
     final $p = ReceivePort();
-    final $c = jni.JObject.fromRef(jni.Jni.newPortContinuation($p));
+    final $c =
+        jni.JObject.fromRef(ProtectedJniExtensions.newPortContinuation($p));
     jni.Jni.accessors.callMethodWithArgs(reference, _id_sayHello1,
         jni.JniCallType.objectType, [string.reference, $c.reference]).object;
     final $o = jni.JObjectPtr.fromAddress(await $p.first);
diff --git a/pkgs/jnigen/test/kotlin_test/generate.dart b/pkgs/jnigen/test/kotlin_test/generate.dart
index 11b89ea53..61686679a 100644
--- a/pkgs/jnigen/test/kotlin_test/generate.dart
+++ b/pkgs/jnigen/test/kotlin_test/generate.dart
@@ -63,7 +63,7 @@ Config getConfig([BindingsType bindingsType = BindingsType.cBased]) {
         structure: OutputStructure.singleFile,
       ),
     ),
-    summarizerOptions: SummarizerOptions(backend: 'asm'),
+    summarizerOptions: SummarizerOptions(backend: SummarizerBackend.asm),
     preamble: preamble,
   );
   return config;
diff --git a/pkgs/jnigen/test/kotlin_test/jni.jar b/pkgs/jnigen/test/kotlin_test/jni.jar
deleted file mode 100644
index 37a1bfc8ee9b578163cffca1479743f667050a80..0000000000000000000000000000000000000000
GIT binary patch
literal 0
HcmV?d00001

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diff --git a/pkgs/jnigen/test/package_resolver_test.dart b/pkgs/jnigen/test/package_resolver_test.dart
index 8053b5aa2..a29e04362 100644
--- a/pkgs/jnigen/test/package_resolver_test.dart
+++ b/pkgs/jnigen/test/package_resolver_test.dart
@@ -20,9 +20,11 @@ void main() async {
   final resolver = Resolver(
     importedClasses: {
       'org.apache.pdfbox.pdmodel.PDDocument': ClassDecl(
+        declKind: DeclKind.classKind,
         binaryName: 'org.apache.pdfbox.pdmodel.PDDocument',
       )..path = 'package:pdfbox/pdfbox.dart',
       'android.os.Process': ClassDecl(
+        declKind: DeclKind.classKind,
         binaryName: 'android.os.Process',
       )..path = 'package:android/os.dart',
     },
@@ -70,8 +72,10 @@ void main() async {
     test(
         'resolve $binaryName',
         () => expect(
-            resolver
-                .resolvePrefix(ClassDecl(binaryName: binaryName)..path = ''),
+            resolver.resolvePrefix(ClassDecl(
+              declKind: DeclKind.classKind,
+              binaryName: binaryName,
+            )..path = ''),
             equals(testCase.expectedName)));
   }
 }
diff --git a/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/dartjni.h b/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/dartjni.h
index c0713af53..cbb1f7f5c 100644
--- a/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/dartjni.h
+++ b/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/dartjni.h
@@ -45,6 +45,7 @@
 #include <windows.h>
 
 typedef CRITICAL_SECTION MutexLock;
+typedef CONDITION_VARIABLE ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   InitializeCriticalSection(lock);
@@ -58,15 +59,32 @@ static inline void release_lock(MutexLock* lock) {
   LeaveCriticalSection(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   DeleteCriticalSection(lock);
 }
 
-#elif defined __DARWIN__ || defined __LINUX__ || defined __ANDROID__ ||        \
+static inline void init_cond(ConditionVariable* cond) {
+  InitializeConditionVariable(cond);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  WakeConditionVariable(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  SleepConditionVariableCS(cond, lock, INFINITE);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  DeleteCriticalSection(cond);
+}
+
+#elif defined __APPLE__ || defined __LINUX__ || defined __ANDROID__ ||         \
     defined __GNUC__
 #include <pthread.h>
 
 typedef pthread_mutex_t MutexLock;
+typedef pthread_cond_t ConditionVariable;
 
 static inline void init_lock(MutexLock* lock) {
   pthread_mutex_init(lock, NULL);
@@ -80,15 +98,48 @@ static inline void release_lock(MutexLock* lock) {
   pthread_mutex_unlock(lock);
 }
 
-static inline void _destroyLock(MutexLock* lock) {
+static inline void destroy_lock(MutexLock* lock) {
   pthread_mutex_destroy(lock);
 }
 
+static inline void init_cond(ConditionVariable* cond) {
+  pthread_cond_init(cond, NULL);
+}
+
+static inline void signal_cond(ConditionVariable* cond) {
+  pthread_cond_signal(cond);
+}
+
+static inline void wait_for(ConditionVariable* cond, MutexLock* lock) {
+  pthread_cond_wait(cond, lock);
+}
+
+static inline void destroy_cond(ConditionVariable* cond) {
+  pthread_cond_destroy(cond);
+}
+
 #else
 
-#error "No locking support; Possibly unsupported platform"
+#error "No locking/condition variable support; Possibly unsupported platform"
+
+#endif
 
+static inline uint64_t thread_id() {
+#ifdef _WIN32
+  return GetCurrentThreadId();
+#elif defined __APPLE__
+  return pthread_mach_thread_np(pthread_self());
+#else
+  return pthread_self();
 #endif
+}
+
+typedef struct CallbackResult {
+  MutexLock lock;
+  ConditionVariable cond;
+  int ready;
+  jobject object;
+} CallbackResult;
 
 typedef struct JniLocks {
   MutexLock classLoadingLock;
@@ -369,6 +420,8 @@ static inline JniResult to_global_ref_result(jobject ref) {
 
 FFI_PLUGIN_EXPORT intptr_t InitDartApiDL(void* data);
 
+FFI_PLUGIN_EXPORT void resultFor(CallbackResult* result, jobject object);
+
 JNIEXPORT void JNICALL
 Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject thiz,
@@ -376,3 +429,18 @@ Java_com_github_dart_1lang_jni_PortContinuation__1resumeWith(JNIEnv* env,
                                                              jobject result);
 FFI_PLUGIN_EXPORT
 JniResult PortContinuation__ctor(int64_t j);
+
+FFI_PLUGIN_EXPORT
+JniResult PortProxy__newInstance(jobject binaryName,
+                                 int64_t port,
+                                 int64_t functionPtr);
+
+JNIEXPORT jobject JNICALL
+Java_com_github_dart_1lang_jni_PortProxy__1invoke(JNIEnv* env,
+                                                  jobject thiz,
+                                                  jlong port,
+                                                  jlong threadId,
+                                                  jlong functionPtr,
+                                                  jobject proxy,
+                                                  jstring methodDescriptor,
+                                                  jobjectArray args);
diff --git a/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/simple_package.c b/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/simple_package.c
index 6c0f3e245..9b6e5e10c 100644
--- a/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/simple_package.c
+++ b/pkgs/jnigen/test/simple_package_test/c_based/c_bindings/simple_package.c
@@ -2310,6 +2310,158 @@ JniResult StringValuedMap__ctor() {
   return to_global_ref_result(_result);
 }
 
+// com.github.dart_lang.jnigen.interfaces.MyInterface
+jclass _c_MyInterface = NULL;
+
+jmethodID _m_MyInterface__voidCallback = NULL;
+FFI_PLUGIN_EXPORT
+JniResult MyInterface__voidCallback(jobject self_, jobject s) {
+  load_env();
+  load_class_global_ref(&_c_MyInterface,
+                        "com/github/dart_lang/jnigen/interfaces/MyInterface");
+  if (_c_MyInterface == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_method(_c_MyInterface, &_m_MyInterface__voidCallback, "voidCallback",
+              "(Ljava/lang/String;)V");
+  if (_m_MyInterface__voidCallback == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  (*jniEnv)->CallVoidMethod(jniEnv, self_, _m_MyInterface__voidCallback, s);
+  return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+}
+
+jmethodID _m_MyInterface__stringCallback = NULL;
+FFI_PLUGIN_EXPORT
+JniResult MyInterface__stringCallback(jobject self_, jobject s) {
+  load_env();
+  load_class_global_ref(&_c_MyInterface,
+                        "com/github/dart_lang/jnigen/interfaces/MyInterface");
+  if (_c_MyInterface == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_method(_c_MyInterface, &_m_MyInterface__stringCallback, "stringCallback",
+              "(Ljava/lang/String;)Ljava/lang/String;");
+  if (_m_MyInterface__stringCallback == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  jobject _result = (*jniEnv)->CallObjectMethod(
+      jniEnv, self_, _m_MyInterface__stringCallback, s);
+  return to_global_ref_result(_result);
+}
+
+jmethodID _m_MyInterface__varCallback = NULL;
+FFI_PLUGIN_EXPORT
+JniResult MyInterface__varCallback(jobject self_, jobject t) {
+  load_env();
+  load_class_global_ref(&_c_MyInterface,
+                        "com/github/dart_lang/jnigen/interfaces/MyInterface");
+  if (_c_MyInterface == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_method(_c_MyInterface, &_m_MyInterface__varCallback, "varCallback",
+              "(Ljava/lang/Object;)Ljava/lang/Object;");
+  if (_m_MyInterface__varCallback == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  jobject _result = (*jniEnv)->CallObjectMethod(jniEnv, self_,
+                                                _m_MyInterface__varCallback, t);
+  return to_global_ref_result(_result);
+}
+
+jmethodID _m_MyInterface__manyPrimitives = NULL;
+FFI_PLUGIN_EXPORT
+JniResult MyInterface__manyPrimitives(jobject self_,
+                                      int32_t a,
+                                      uint8_t b,
+                                      uint16_t c,
+                                      double d) {
+  load_env();
+  load_class_global_ref(&_c_MyInterface,
+                        "com/github/dart_lang/jnigen/interfaces/MyInterface");
+  if (_c_MyInterface == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_method(_c_MyInterface, &_m_MyInterface__manyPrimitives, "manyPrimitives",
+              "(IZCD)J");
+  if (_m_MyInterface__manyPrimitives == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  int64_t _result = (*jniEnv)->CallLongMethod(
+      jniEnv, self_, _m_MyInterface__manyPrimitives, a, b, c, d);
+  return (JniResult){.value = {.j = _result}, .exception = check_exception()};
+}
+
+// com.github.dart_lang.jnigen.interfaces.MyInterfaceConsumer
+jclass _c_MyInterfaceConsumer = NULL;
+
+jmethodID _m_MyInterfaceConsumer__ctor = NULL;
+FFI_PLUGIN_EXPORT
+JniResult MyInterfaceConsumer__ctor() {
+  load_env();
+  load_class_global_ref(
+      &_c_MyInterfaceConsumer,
+      "com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer");
+  if (_c_MyInterfaceConsumer == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_method(_c_MyInterfaceConsumer, &_m_MyInterfaceConsumer__ctor, "<init>",
+              "()V");
+  if (_m_MyInterfaceConsumer__ctor == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  jobject _result = (*jniEnv)->NewObject(jniEnv, _c_MyInterfaceConsumer,
+                                         _m_MyInterfaceConsumer__ctor);
+  return to_global_ref_result(_result);
+}
+
+jmethodID _m_MyInterfaceConsumer__consumeOnAnotherThread = NULL;
+FFI_PLUGIN_EXPORT
+JniResult MyInterfaceConsumer__consumeOnAnotherThread(jobject myInterface,
+                                                      jobject s,
+                                                      int32_t a,
+                                                      uint8_t b,
+                                                      uint16_t c,
+                                                      double d,
+                                                      jobject t) {
+  load_env();
+  load_class_global_ref(
+      &_c_MyInterfaceConsumer,
+      "com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer");
+  if (_c_MyInterfaceConsumer == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_static_method(_c_MyInterfaceConsumer,
+                     &_m_MyInterfaceConsumer__consumeOnAnotherThread,
+                     "consumeOnAnotherThread",
+                     "(Lcom/github/dart_lang/jnigen/interfaces/"
+                     "MyInterface;Ljava/lang/String;IZCDLjava/lang/Object;)V");
+  if (_m_MyInterfaceConsumer__consumeOnAnotherThread == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  (*jniEnv)->CallStaticVoidMethod(
+      jniEnv, _c_MyInterfaceConsumer,
+      _m_MyInterfaceConsumer__consumeOnAnotherThread, myInterface, s, a, b, c,
+      d, t);
+  return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+}
+
+jmethodID _m_MyInterfaceConsumer__consumeOnSameThread = NULL;
+FFI_PLUGIN_EXPORT
+JniResult MyInterfaceConsumer__consumeOnSameThread(jobject myInterface,
+                                                   jobject s,
+                                                   int32_t a,
+                                                   uint8_t b,
+                                                   uint16_t c,
+                                                   double d,
+                                                   jobject t) {
+  load_env();
+  load_class_global_ref(
+      &_c_MyInterfaceConsumer,
+      "com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer");
+  if (_c_MyInterfaceConsumer == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  load_static_method(_c_MyInterfaceConsumer,
+                     &_m_MyInterfaceConsumer__consumeOnSameThread,
+                     "consumeOnSameThread",
+                     "(Lcom/github/dart_lang/jnigen/interfaces/"
+                     "MyInterface;Ljava/lang/String;IZCDLjava/lang/Object;)V");
+  if (_m_MyInterfaceConsumer__consumeOnSameThread == NULL)
+    return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+  (*jniEnv)->CallStaticVoidMethod(jniEnv, _c_MyInterfaceConsumer,
+                                  _m_MyInterfaceConsumer__consumeOnSameThread,
+                                  myInterface, s, a, b, c, d, t);
+  return (JniResult){.value = {.j = 0}, .exception = check_exception()};
+}
+
 // com.github.dart_lang.jnigen.annotations.JsonSerializable$Case
 jclass _c_JsonSerializable_Case = NULL;
 
diff --git a/pkgs/jnigen/test/simple_package_test/c_based/dart_bindings/simple_package.dart b/pkgs/jnigen/test/simple_package_test/c_based/dart_bindings/simple_package.dart
index d0ad47c7d..7cb011083 100644
--- a/pkgs/jnigen/test/simple_package_test/c_based/dart_bindings/simple_package.dart
+++ b/pkgs/jnigen/test/simple_package_test/c_based/dart_bindings/simple_package.dart
@@ -16,6 +16,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
@@ -2827,6 +2828,372 @@ class $StringValuedMapType<$K extends jni.JObject>
   }
 }
 
+/// from: com.github.dart_lang.jnigen.interfaces.MyInterface
+class MyInterface<$T extends jni.JObject> extends jni.JObject {
+  @override
+  late final jni.JObjType<MyInterface<$T>> $type = type(T);
+
+  final jni.JObjType<$T> T;
+
+  MyInterface.fromRef(
+    this.T,
+    jni.JObjectPtr ref,
+  ) : super.fromRef(ref);
+
+  /// The type which includes information such as the signature of this class.
+  static $MyInterfaceType<$T> type<$T extends jni.JObject>(
+    jni.JObjType<$T> T,
+  ) {
+    return $MyInterfaceType(
+      T,
+    );
+  }
+
+  static final _voidCallback = jniLookup<
+          ffi.NativeFunction<
+              jni.JniResult Function(ffi.Pointer<ffi.Void>,
+                  ffi.Pointer<ffi.Void>)>>("MyInterface__voidCallback")
+      .asFunction<
+          jni.JniResult Function(
+              ffi.Pointer<ffi.Void>, ffi.Pointer<ffi.Void>)>();
+
+  /// from: public abstract void voidCallback(java.lang.String s)
+  void voidCallback(
+    jni.JString s,
+  ) {
+    return _voidCallback(reference, s.reference).check();
+  }
+
+  static final _stringCallback = jniLookup<
+          ffi.NativeFunction<
+              jni.JniResult Function(ffi.Pointer<ffi.Void>,
+                  ffi.Pointer<ffi.Void>)>>("MyInterface__stringCallback")
+      .asFunction<
+          jni.JniResult Function(
+              ffi.Pointer<ffi.Void>, ffi.Pointer<ffi.Void>)>();
+
+  /// from: public abstract java.lang.String stringCallback(java.lang.String s)
+  /// The returned object must be deleted after use, by calling the `delete` method.
+  jni.JString stringCallback(
+    jni.JString s,
+  ) {
+    return const jni.JStringType()
+        .fromRef(_stringCallback(reference, s.reference).object);
+  }
+
+  static final _varCallback = jniLookup<
+          ffi.NativeFunction<
+              jni.JniResult Function(ffi.Pointer<ffi.Void>,
+                  ffi.Pointer<ffi.Void>)>>("MyInterface__varCallback")
+      .asFunction<
+          jni.JniResult Function(
+              ffi.Pointer<ffi.Void>, ffi.Pointer<ffi.Void>)>();
+
+  /// from: public abstract T varCallback(T t)
+  /// The returned object must be deleted after use, by calling the `delete` method.
+  $T varCallback(
+    $T t,
+  ) {
+    return T.fromRef(_varCallback(reference, t.reference).object);
+  }
+
+  static final _manyPrimitives = jniLookup<
+          ffi.NativeFunction<
+              jni.JniResult Function(
+                  ffi.Pointer<ffi.Void>,
+                  ffi.Int32,
+                  ffi.Uint8,
+                  ffi.Uint16,
+                  ffi.Double)>>("MyInterface__manyPrimitives")
+      .asFunction<
+          jni.JniResult Function(
+              ffi.Pointer<ffi.Void>, int, int, int, double)>();
+
+  /// from: public abstract long manyPrimitives(int a, boolean b, char c, double d)
+  int manyPrimitives(
+    int a,
+    bool b,
+    int c,
+    double d,
+  ) {
+    return _manyPrimitives(reference, a, b ? 1 : 0, c, d).long;
+  }
+
+  /// Maps a specific port to the implemented methods.
+  static final Map<int, Map<String, Function>> _$methods = {};
+
+  /// Maps a specific port to the type parameters.
+  static final Map<int, Map<String, jni.JObjType>> _$types = {};
+
+  ReceivePort? _$p;
+
+  static final Finalizer<ReceivePort> _$finalizer = Finalizer(($p) {
+    _$methods.remove($p.sendPort.nativePort);
+    _$types.remove($p.sendPort.nativePort);
+    $p.close();
+  });
+
+  @override
+  void delete() {
+    _$methods.remove(_$p?.sendPort.nativePort);
+    _$types.remove(_$p?.sendPort.nativePort);
+    _$p?.close();
+    _$finalizer.detach(this);
+    super.delete();
+  }
+
+  static jni.JObjectPtr _$invoke(
+    int port,
+    jni.JObjectPtr descriptor,
+    jni.JObjectPtr args,
+  ) {
+    return _$invokeMethod(
+      port,
+      $MethodInvocation.fromAddresses(
+        0,
+        descriptor.address,
+        args.address,
+      ),
+    );
+  }
+
+  static final ffi.Pointer<
+          ffi.NativeFunction<
+              jni.JObjectPtr Function(
+                  ffi.Uint64, jni.JObjectPtr, jni.JObjectPtr)>>
+      _$invokePointer = ffi.Pointer.fromFunction(_$invoke);
+
+  static ffi.Pointer<ffi.Void> _$invokeMethod(
+    int $p,
+    $MethodInvocation $i,
+  ) {
+    final $d = $i.methodDescriptor.toDartString(deleteOriginal: true);
+    final $a = $i.args;
+    if ($d == r"voidCallback(Ljava/lang/String;)V") {
+      _$methods[$p]![$d]!(
+        $a[0].castTo(const jni.JStringType(), deleteOriginal: true),
+      );
+      return jni.nullptr;
+    }
+    if ($d == r"stringCallback(Ljava/lang/String;)Ljava/lang/String;") {
+      final $r = _$methods[$p]![$d]!(
+        $a[0].castTo(const jni.JStringType(), deleteOriginal: true),
+      );
+      return $r.reference;
+    }
+    if ($d == r"varCallback(Ljava/lang/Object;)Ljava/lang/Object;") {
+      final $r = _$methods[$p]![$d]!(
+        $a[0].castTo(_$types[$p]!["T"]!, deleteOriginal: true),
+      );
+      return $r.reference;
+    }
+    if ($d == r"manyPrimitives(IZCD)J") {
+      final $r = _$methods[$p]![$d]!(
+        $a[0]
+            .castTo(const jni.JIntegerType(), deleteOriginal: true)
+            .intValue(deleteOriginal: true),
+        $a[1]
+            .castTo(const jni.JBooleanType(), deleteOriginal: true)
+            .booleanValue(deleteOriginal: true),
+        $a[2]
+            .castTo(const jni.JCharacterType(), deleteOriginal: true)
+            .charValue(deleteOriginal: true),
+        $a[3]
+            .castTo(const jni.JDoubleType(), deleteOriginal: true)
+            .doubleValue(deleteOriginal: true),
+      );
+      return jni.JLong($r).reference;
+    }
+    return jni.nullptr;
+  }
+
+  factory MyInterface.implement({
+    required jni.JObjType<$T> T,
+    required void Function(jni.JString s) voidCallback,
+    required jni.JString Function(jni.JString s) stringCallback,
+    required $T Function($T t) varCallback,
+    required int Function(int a, bool b, int c, double d) manyPrimitives,
+  }) {
+    final $p = ReceivePort();
+    final $x = MyInterface.fromRef(
+      T,
+      ProtectedJniExtensions.newPortProxy(
+        r"com.github.dart_lang.jnigen.interfaces.MyInterface",
+        $p,
+        _$invokePointer,
+      ),
+    ).._$p = $p;
+    final $a = $p.sendPort.nativePort;
+    _$types[$a] = {};
+    _$methods[$a] = {};
+    _$types[$a]!["T"] = T;
+    _$methods[$a]![r"voidCallback(Ljava/lang/String;)V"] = voidCallback;
+    _$methods[$a]![r"stringCallback(Ljava/lang/String;)Ljava/lang/String;"] =
+        stringCallback;
+    _$methods[$a]![r"varCallback(Ljava/lang/Object;)Ljava/lang/Object;"] =
+        varCallback;
+    _$methods[$a]![r"manyPrimitives(IZCD)J"] = manyPrimitives;
+    _$finalizer.attach($x, $p, detach: $x);
+    $p.listen(($m) {
+      final $i = $MethodInvocation.fromMessage($m);
+      final $r = _$invokeMethod($p.sendPort.nativePort, $i);
+      ProtectedJniExtensions.returnResult($i.result, $r);
+    });
+    return $x;
+  }
+}
+
+class $MyInterfaceType<$T extends jni.JObject>
+    extends jni.JObjType<MyInterface<$T>> {
+  final jni.JObjType<$T> T;
+
+  const $MyInterfaceType(
+    this.T,
+  );
+
+  @override
+  String get signature =>
+      r"Lcom/github/dart_lang/jnigen/interfaces/MyInterface;";
+
+  @override
+  MyInterface<$T> fromRef(jni.JObjectPtr ref) => MyInterface.fromRef(T, ref);
+
+  @override
+  jni.JObjType get superType => const jni.JObjectType();
+
+  @override
+  final superCount = 1;
+
+  @override
+  int get hashCode => Object.hash($MyInterfaceType, T);
+
+  @override
+  bool operator ==(Object other) {
+    return other.runtimeType == ($MyInterfaceType<$T>) &&
+        other is $MyInterfaceType<$T> &&
+        T == other.T;
+  }
+}
+
+/// from: com.github.dart_lang.jnigen.interfaces.MyInterfaceConsumer
+class MyInterfaceConsumer extends jni.JObject {
+  @override
+  late final jni.JObjType<MyInterfaceConsumer> $type = type;
+
+  MyInterfaceConsumer.fromRef(
+    jni.JObjectPtr ref,
+  ) : super.fromRef(ref);
+
+  /// The type which includes information such as the signature of this class.
+  static const type = $MyInterfaceConsumerType();
+  static final _ctor = jniLookup<ffi.NativeFunction<jni.JniResult Function()>>(
+          "MyInterfaceConsumer__ctor")
+      .asFunction<jni.JniResult Function()>();
+
+  /// from: public void <init>()
+  /// The returned object must be deleted after use, by calling the `delete` method.
+  factory MyInterfaceConsumer() {
+    return MyInterfaceConsumer.fromRef(_ctor().object);
+  }
+
+  static final _consumeOnAnotherThread = jniLookup<
+              ffi.NativeFunction<
+                  jni.JniResult Function(
+                      ffi.Pointer<ffi.Void>,
+                      ffi.Pointer<ffi.Void>,
+                      ffi.Int32,
+                      ffi.Uint8,
+                      ffi.Uint16,
+                      ffi.Double,
+                      ffi.Pointer<ffi.Void>)>>(
+          "MyInterfaceConsumer__consumeOnAnotherThread")
+      .asFunction<
+          jni.JniResult Function(ffi.Pointer<ffi.Void>, ffi.Pointer<ffi.Void>,
+              int, int, int, double, ffi.Pointer<ffi.Void>)>();
+
+  /// from: static public void consumeOnAnotherThread(com.github.dart_lang.jnigen.interfaces.MyInterface<T> myInterface, java.lang.String s, int a, boolean b, char c, double d, T t)
+  static void consumeOnAnotherThread<$T extends jni.JObject>(
+    MyInterface<$T> myInterface,
+    jni.JString s,
+    int a,
+    bool b,
+    int c,
+    double d,
+    $T t, {
+    jni.JObjType<$T>? T,
+  }) {
+    T ??= jni.lowestCommonSuperType([
+      t.$type,
+      (myInterface.$type as $MyInterfaceType).T,
+    ]) as jni.JObjType<$T>;
+    return _consumeOnAnotherThread(
+            myInterface.reference, s.reference, a, b ? 1 : 0, c, d, t.reference)
+        .check();
+  }
+
+  static final _consumeOnSameThread = jniLookup<
+              ffi.NativeFunction<
+                  jni.JniResult Function(
+                      ffi.Pointer<ffi.Void>,
+                      ffi.Pointer<ffi.Void>,
+                      ffi.Int32,
+                      ffi.Uint8,
+                      ffi.Uint16,
+                      ffi.Double,
+                      ffi.Pointer<ffi.Void>)>>(
+          "MyInterfaceConsumer__consumeOnSameThread")
+      .asFunction<
+          jni.JniResult Function(ffi.Pointer<ffi.Void>, ffi.Pointer<ffi.Void>,
+              int, int, int, double, ffi.Pointer<ffi.Void>)>();
+
+  /// from: static public void consumeOnSameThread(com.github.dart_lang.jnigen.interfaces.MyInterface<T> myInterface, java.lang.String s, int a, boolean b, char c, double d, T t)
+  static void consumeOnSameThread<$T extends jni.JObject>(
+    MyInterface<$T> myInterface,
+    jni.JString s,
+    int a,
+    bool b,
+    int c,
+    double d,
+    $T t, {
+    jni.JObjType<$T>? T,
+  }) {
+    T ??= jni.lowestCommonSuperType([
+      t.$type,
+      (myInterface.$type as $MyInterfaceType).T,
+    ]) as jni.JObjType<$T>;
+    return _consumeOnSameThread(
+            myInterface.reference, s.reference, a, b ? 1 : 0, c, d, t.reference)
+        .check();
+  }
+}
+
+class $MyInterfaceConsumerType extends jni.JObjType<MyInterfaceConsumer> {
+  const $MyInterfaceConsumerType();
+
+  @override
+  String get signature =>
+      r"Lcom/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer;";
+
+  @override
+  MyInterfaceConsumer fromRef(jni.JObjectPtr ref) =>
+      MyInterfaceConsumer.fromRef(ref);
+
+  @override
+  jni.JObjType get superType => const jni.JObjectType();
+
+  @override
+  final superCount = 1;
+
+  @override
+  int get hashCode => ($MyInterfaceConsumerType).hashCode;
+
+  @override
+  bool operator ==(Object other) {
+    return other.runtimeType == ($MyInterfaceConsumerType) &&
+        other is $MyInterfaceConsumerType;
+  }
+}
+
 /// from: com.github.dart_lang.jnigen.annotations.JsonSerializable$Case
 class JsonSerializable_Case extends jni.JObject {
   @override
diff --git a/pkgs/jnigen/test/simple_package_test/dart_only/dart_bindings/simple_package.dart b/pkgs/jnigen/test/simple_package_test/dart_only/dart_bindings/simple_package.dart
index 3394d3d92..7befe1b98 100644
--- a/pkgs/jnigen/test/simple_package_test/dart_only/dart_bindings/simple_package.dart
+++ b/pkgs/jnigen/test/simple_package_test/dart_only/dart_bindings/simple_package.dart
@@ -16,6 +16,7 @@
 // ignore_for_file: unused_element
 // ignore_for_file: unused_field
 // ignore_for_file: unused_import
+// ignore_for_file: unused_local_variable
 // ignore_for_file: unused_shown_name
 
 import "dart:isolate" show ReceivePort;
@@ -2674,6 +2675,361 @@ class $StringValuedMapType<$K extends jni.JObject>
   }
 }
 
+/// from: com.github.dart_lang.jnigen.interfaces.MyInterface
+class MyInterface<$T extends jni.JObject> extends jni.JObject {
+  @override
+  late final jni.JObjType<MyInterface<$T>> $type = type(T);
+
+  final jni.JObjType<$T> T;
+
+  MyInterface.fromRef(
+    this.T,
+    jni.JObjectPtr ref,
+  ) : super.fromRef(ref);
+
+  static final _class =
+      jni.Jni.findJClass(r"com/github/dart_lang/jnigen/interfaces/MyInterface");
+
+  /// The type which includes information such as the signature of this class.
+  static $MyInterfaceType<$T> type<$T extends jni.JObject>(
+    jni.JObjType<$T> T,
+  ) {
+    return $MyInterfaceType(
+      T,
+    );
+  }
+
+  static final _id_voidCallback = jni.Jni.accessors.getMethodIDOf(
+      _class.reference, r"voidCallback", r"(Ljava/lang/String;)V");
+
+  /// from: public abstract void voidCallback(java.lang.String s)
+  void voidCallback(
+    jni.JString s,
+  ) {
+    return jni.Jni.accessors.callMethodWithArgs(reference, _id_voidCallback,
+        jni.JniCallType.voidType, [s.reference]).check();
+  }
+
+  static final _id_stringCallback = jni.Jni.accessors.getMethodIDOf(
+      _class.reference,
+      r"stringCallback",
+      r"(Ljava/lang/String;)Ljava/lang/String;");
+
+  /// from: public abstract java.lang.String stringCallback(java.lang.String s)
+  /// The returned object must be deleted after use, by calling the `delete` method.
+  jni.JString stringCallback(
+    jni.JString s,
+  ) {
+    return const jni.JStringType().fromRef(jni.Jni.accessors.callMethodWithArgs(
+        reference,
+        _id_stringCallback,
+        jni.JniCallType.objectType,
+        [s.reference]).object);
+  }
+
+  static final _id_varCallback = jni.Jni.accessors.getMethodIDOf(
+      _class.reference,
+      r"varCallback",
+      r"(Ljava/lang/Object;)Ljava/lang/Object;");
+
+  /// from: public abstract T varCallback(T t)
+  /// The returned object must be deleted after use, by calling the `delete` method.
+  $T varCallback(
+    $T t,
+  ) {
+    return T.fromRef(jni.Jni.accessors.callMethodWithArgs(reference,
+        _id_varCallback, jni.JniCallType.objectType, [t.reference]).object);
+  }
+
+  static final _id_manyPrimitives = jni.Jni.accessors
+      .getMethodIDOf(_class.reference, r"manyPrimitives", r"(IZCD)J");
+
+  /// from: public abstract long manyPrimitives(int a, boolean b, char c, double d)
+  int manyPrimitives(
+    int a,
+    bool b,
+    int c,
+    double d,
+  ) {
+    return jni.Jni.accessors.callMethodWithArgs(
+        reference,
+        _id_manyPrimitives,
+        jni.JniCallType.longType,
+        [jni.JValueInt(a), b ? 1 : 0, jni.JValueChar(c), d]).long;
+  }
+
+  /// Maps a specific port to the implemented methods.
+  static final Map<int, Map<String, Function>> _$methods = {};
+
+  /// Maps a specific port to the type parameters.
+  static final Map<int, Map<String, jni.JObjType>> _$types = {};
+
+  ReceivePort? _$p;
+
+  static final Finalizer<ReceivePort> _$finalizer = Finalizer(($p) {
+    _$methods.remove($p.sendPort.nativePort);
+    _$types.remove($p.sendPort.nativePort);
+    $p.close();
+  });
+
+  @override
+  void delete() {
+    _$methods.remove(_$p?.sendPort.nativePort);
+    _$types.remove(_$p?.sendPort.nativePort);
+    _$p?.close();
+    _$finalizer.detach(this);
+    super.delete();
+  }
+
+  static jni.JObjectPtr _$invoke(
+    int port,
+    jni.JObjectPtr descriptor,
+    jni.JObjectPtr args,
+  ) {
+    return _$invokeMethod(
+      port,
+      $MethodInvocation.fromAddresses(
+        0,
+        descriptor.address,
+        args.address,
+      ),
+    );
+  }
+
+  static final ffi.Pointer<
+          ffi.NativeFunction<
+              jni.JObjectPtr Function(
+                  ffi.Uint64, jni.JObjectPtr, jni.JObjectPtr)>>
+      _$invokePointer = ffi.Pointer.fromFunction(_$invoke);
+
+  static ffi.Pointer<ffi.Void> _$invokeMethod(
+    int $p,
+    $MethodInvocation $i,
+  ) {
+    final $d = $i.methodDescriptor.toDartString(deleteOriginal: true);
+    final $a = $i.args;
+    if ($d == r"voidCallback(Ljava/lang/String;)V") {
+      _$methods[$p]![$d]!(
+        $a[0].castTo(const jni.JStringType(), deleteOriginal: true),
+      );
+      return jni.nullptr;
+    }
+    if ($d == r"stringCallback(Ljava/lang/String;)Ljava/lang/String;") {
+      final $r = _$methods[$p]![$d]!(
+        $a[0].castTo(const jni.JStringType(), deleteOriginal: true),
+      );
+      return $r.reference;
+    }
+    if ($d == r"varCallback(Ljava/lang/Object;)Ljava/lang/Object;") {
+      final $r = _$methods[$p]![$d]!(
+        $a[0].castTo(_$types[$p]!["T"]!, deleteOriginal: true),
+      );
+      return $r.reference;
+    }
+    if ($d == r"manyPrimitives(IZCD)J") {
+      final $r = _$methods[$p]![$d]!(
+        $a[0]
+            .castTo(const jni.JIntegerType(), deleteOriginal: true)
+            .intValue(deleteOriginal: true),
+        $a[1]
+            .castTo(const jni.JBooleanType(), deleteOriginal: true)
+            .booleanValue(deleteOriginal: true),
+        $a[2]
+            .castTo(const jni.JCharacterType(), deleteOriginal: true)
+            .charValue(deleteOriginal: true),
+        $a[3]
+            .castTo(const jni.JDoubleType(), deleteOriginal: true)
+            .doubleValue(deleteOriginal: true),
+      );
+      return jni.JLong($r).reference;
+    }
+    return jni.nullptr;
+  }
+
+  factory MyInterface.implement({
+    required jni.JObjType<$T> T,
+    required void Function(jni.JString s) voidCallback,
+    required jni.JString Function(jni.JString s) stringCallback,
+    required $T Function($T t) varCallback,
+    required int Function(int a, bool b, int c, double d) manyPrimitives,
+  }) {
+    final $p = ReceivePort();
+    final $x = MyInterface.fromRef(
+      T,
+      ProtectedJniExtensions.newPortProxy(
+        r"com.github.dart_lang.jnigen.interfaces.MyInterface",
+        $p,
+        _$invokePointer,
+      ),
+    ).._$p = $p;
+    final $a = $p.sendPort.nativePort;
+    _$types[$a] = {};
+    _$methods[$a] = {};
+    _$types[$a]!["T"] = T;
+    _$methods[$a]![r"voidCallback(Ljava/lang/String;)V"] = voidCallback;
+    _$methods[$a]![r"stringCallback(Ljava/lang/String;)Ljava/lang/String;"] =
+        stringCallback;
+    _$methods[$a]![r"varCallback(Ljava/lang/Object;)Ljava/lang/Object;"] =
+        varCallback;
+    _$methods[$a]![r"manyPrimitives(IZCD)J"] = manyPrimitives;
+    _$finalizer.attach($x, $p, detach: $x);
+    $p.listen(($m) {
+      final $i = $MethodInvocation.fromMessage($m);
+      final $r = _$invokeMethod($p.sendPort.nativePort, $i);
+      ProtectedJniExtensions.returnResult($i.result, $r);
+    });
+    return $x;
+  }
+}
+
+class $MyInterfaceType<$T extends jni.JObject>
+    extends jni.JObjType<MyInterface<$T>> {
+  final jni.JObjType<$T> T;
+
+  const $MyInterfaceType(
+    this.T,
+  );
+
+  @override
+  String get signature =>
+      r"Lcom/github/dart_lang/jnigen/interfaces/MyInterface;";
+
+  @override
+  MyInterface<$T> fromRef(jni.JObjectPtr ref) => MyInterface.fromRef(T, ref);
+
+  @override
+  jni.JObjType get superType => const jni.JObjectType();
+
+  @override
+  final superCount = 1;
+
+  @override
+  int get hashCode => Object.hash($MyInterfaceType, T);
+
+  @override
+  bool operator ==(Object other) {
+    return other.runtimeType == ($MyInterfaceType<$T>) &&
+        other is $MyInterfaceType<$T> &&
+        T == other.T;
+  }
+}
+
+/// from: com.github.dart_lang.jnigen.interfaces.MyInterfaceConsumer
+class MyInterfaceConsumer extends jni.JObject {
+  @override
+  late final jni.JObjType<MyInterfaceConsumer> $type = type;
+
+  MyInterfaceConsumer.fromRef(
+    jni.JObjectPtr ref,
+  ) : super.fromRef(ref);
+
+  static final _class = jni.Jni.findJClass(
+      r"com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer");
+
+  /// The type which includes information such as the signature of this class.
+  static const type = $MyInterfaceConsumerType();
+  static final _id_ctor =
+      jni.Jni.accessors.getMethodIDOf(_class.reference, r"<init>", r"()V");
+
+  /// from: public void <init>()
+  /// The returned object must be deleted after use, by calling the `delete` method.
+  factory MyInterfaceConsumer() {
+    return MyInterfaceConsumer.fromRef(jni.Jni.accessors
+        .newObjectWithArgs(_class.reference, _id_ctor, []).object);
+  }
+
+  static final _id_consumeOnAnotherThread = jni.Jni.accessors.getStaticMethodIDOf(
+      _class.reference,
+      r"consumeOnAnotherThread",
+      r"(Lcom/github/dart_lang/jnigen/interfaces/MyInterface;Ljava/lang/String;IZCDLjava/lang/Object;)V");
+
+  /// from: static public void consumeOnAnotherThread(com.github.dart_lang.jnigen.interfaces.MyInterface<T> myInterface, java.lang.String s, int a, boolean b, char c, double d, T t)
+  static void consumeOnAnotherThread<$T extends jni.JObject>(
+    MyInterface<$T> myInterface,
+    jni.JString s,
+    int a,
+    bool b,
+    int c,
+    double d,
+    $T t, {
+    jni.JObjType<$T>? T,
+  }) {
+    T ??= jni.lowestCommonSuperType([
+      t.$type,
+      (myInterface.$type as $MyInterfaceType).T,
+    ]) as jni.JObjType<$T>;
+    return jni.Jni.accessors.callStaticMethodWithArgs(_class.reference,
+        _id_consumeOnAnotherThread, jni.JniCallType.voidType, [
+      myInterface.reference,
+      s.reference,
+      jni.JValueInt(a),
+      b ? 1 : 0,
+      jni.JValueChar(c),
+      d,
+      t.reference
+    ]).check();
+  }
+
+  static final _id_consumeOnSameThread = jni.Jni.accessors.getStaticMethodIDOf(
+      _class.reference,
+      r"consumeOnSameThread",
+      r"(Lcom/github/dart_lang/jnigen/interfaces/MyInterface;Ljava/lang/String;IZCDLjava/lang/Object;)V");
+
+  /// from: static public void consumeOnSameThread(com.github.dart_lang.jnigen.interfaces.MyInterface<T> myInterface, java.lang.String s, int a, boolean b, char c, double d, T t)
+  static void consumeOnSameThread<$T extends jni.JObject>(
+    MyInterface<$T> myInterface,
+    jni.JString s,
+    int a,
+    bool b,
+    int c,
+    double d,
+    $T t, {
+    jni.JObjType<$T>? T,
+  }) {
+    T ??= jni.lowestCommonSuperType([
+      t.$type,
+      (myInterface.$type as $MyInterfaceType).T,
+    ]) as jni.JObjType<$T>;
+    return jni.Jni.accessors.callStaticMethodWithArgs(
+        _class.reference, _id_consumeOnSameThread, jni.JniCallType.voidType, [
+      myInterface.reference,
+      s.reference,
+      jni.JValueInt(a),
+      b ? 1 : 0,
+      jni.JValueChar(c),
+      d,
+      t.reference
+    ]).check();
+  }
+}
+
+class $MyInterfaceConsumerType extends jni.JObjType<MyInterfaceConsumer> {
+  const $MyInterfaceConsumerType();
+
+  @override
+  String get signature =>
+      r"Lcom/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer;";
+
+  @override
+  MyInterfaceConsumer fromRef(jni.JObjectPtr ref) =>
+      MyInterfaceConsumer.fromRef(ref);
+
+  @override
+  jni.JObjType get superType => const jni.JObjectType();
+
+  @override
+  final superCount = 1;
+
+  @override
+  int get hashCode => ($MyInterfaceConsumerType).hashCode;
+
+  @override
+  bool operator ==(Object other) {
+    return other.runtimeType == ($MyInterfaceConsumerType) &&
+        other is $MyInterfaceConsumerType;
+  }
+}
+
 /// from: com.github.dart_lang.jnigen.annotations.JsonSerializable$Case
 class JsonSerializable_Case extends jni.JObject {
   @override
diff --git a/pkgs/jnigen/test/simple_package_test/generate.dart b/pkgs/jnigen/test/simple_package_test/generate.dart
index 18c38e0d3..ce38009d3 100644
--- a/pkgs/jnigen/test/simple_package_test/generate.dart
+++ b/pkgs/jnigen/test/simple_package_test/generate.dart
@@ -4,6 +4,7 @@
 
 import 'dart:io';
 
+import 'package:jnigen/src/config/experiments.dart';
 import 'package:logging/logging.dart';
 import 'package:path/path.dart';
 import 'package:jnigen/jnigen.dart';
@@ -31,6 +32,8 @@ var javaFiles = [
   join(javaPrefix, 'generics', 'StringStack.java'),
   join(javaPrefix, 'generics', 'StringValuedMap.java'),
   join(javaPrefix, 'generics', 'StringKeyedMap.java'),
+  join(javaPrefix, 'interfaces', 'MyInterface.java'),
+  join(javaPrefix, 'interfaces', 'MyInterfaceConsumer.java'),
   join(javaPrefix, 'annotations', 'JsonSerializable.java'),
   join(javaPrefix, 'annotations', 'MyDataClass.java'),
 ];
@@ -57,6 +60,7 @@ Config getConfig([BindingsType bindingsType = BindingsType.cBased]) {
       'com.github.dart_lang.jnigen.simple_package',
       'com.github.dart_lang.jnigen.pkg2',
       'com.github.dart_lang.jnigen.generics',
+      'com.github.dart_lang.jnigen.interfaces',
       'com.github.dart_lang.jnigen.annotations',
     ],
     logLevel: Level.INFO,
@@ -72,6 +76,7 @@ Config getConfig([BindingsType bindingsType = BindingsType.cBased]) {
       ),
     ),
     preamble: preamble,
+    experiments: {Experiment.interfaceImplementation},
   );
   return config;
 }
diff --git a/pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterface.java b/pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterface.java
new file mode 100644
index 000000000..97b243e52
--- /dev/null
+++ b/pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterface.java
@@ -0,0 +1,15 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.github.dart_lang.jnigen.interfaces;
+
+public interface MyInterface<T> {
+  void voidCallback(String s);
+
+  String stringCallback(String s);
+
+  T varCallback(T t);
+
+  long manyPrimitives(int a, boolean b, char c, double d);
+}
diff --git a/pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer.java b/pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer.java
new file mode 100644
index 000000000..b4eeb2fda
--- /dev/null
+++ b/pkgs/jnigen/test/simple_package_test/java/com/github/dart_lang/jnigen/interfaces/MyInterfaceConsumer.java
@@ -0,0 +1,21 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.github.dart_lang.jnigen.interfaces;
+
+public class MyInterfaceConsumer {
+  public static <T> void consumeOnAnotherThread(
+      MyInterface<T> myInterface, String s, int a, boolean b, char c, double d, T t) {
+    var thread = new Thread(() -> consumeOnSameThread(myInterface, s, a, b, c, d, t));
+    thread.start();
+  }
+
+  public static <T> void consumeOnSameThread(
+      MyInterface<T> myInterface, String s, int a, boolean b, char c, double d, T t) {
+    String result = myInterface.stringCallback(s);
+    myInterface.voidCallback(result);
+    myInterface.manyPrimitives(a, b, c, d);
+    myInterface.varCallback(t);
+  }
+}
diff --git a/pkgs/jnigen/test/simple_package_test/runtime_test_registrant.dart b/pkgs/jnigen/test/simple_package_test/runtime_test_registrant.dart
index f3075ac79..cd6f99970 100644
--- a/pkgs/jnigen/test/simple_package_test/runtime_test_registrant.dart
+++ b/pkgs/jnigen/test/simple_package_test/runtime_test_registrant.dart
@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:async';
 import 'dart:io';
 
 import 'package:test/test.dart';
@@ -528,6 +529,74 @@ void registerTests(String groupName, TestRunnerCallback test) {
       });
     });
   });
+
+  group('interface implementation', () {
+    for (final method in {
+      'another thread': MyInterfaceConsumer.consumeOnAnotherThread,
+      'the same thread': MyInterfaceConsumer.consumeOnSameThread,
+    }.entries) {
+      test('MyInterface.implement on ${method.key}', () async {
+        final voidCallbackResult = Completer<JString>();
+        final varCallbackResult = Completer<JInteger>();
+        final manyPrimitivesResult = Completer<int>();
+        // We can use this trick to access self, instead of generating a `thiz`
+        // or `self` argument for each one of the callbacks.
+        late final MyInterface<JInteger> myInterface;
+        myInterface = MyInterface.implement(
+          voidCallback: (s) {
+            voidCallbackResult.complete(s);
+          },
+          stringCallback: (s) {
+            return (s.toDartString(deleteOriginal: true) * 2).toJString();
+          },
+          varCallback: (JInteger t) {
+            final result = (t.intValue(deleteOriginal: true) * 2).toJInteger();
+            varCallbackResult.complete(result);
+            return result;
+          },
+          manyPrimitives: (a, b, c, d) {
+            if (b) {
+              final result = a + c + d.toInt();
+              manyPrimitivesResult.complete(result);
+              return result;
+            } else {
+              // Call self, add to [a] when [b] is false and change b to true.
+              return myInterface.manyPrimitives(a + 1, true, c, d);
+            }
+          },
+          T: JInteger.type,
+        );
+        // [stringCallback] is going to be called first using [s].
+        // The result of it is going to be used as the argument for
+        // [voidCallback].
+        // The other two methods will be called individually using the passed
+        // arguments afterwards.
+        method.value(
+          myInterface,
+          // For stringCallback:
+          'hello'.toJString(),
+          // For manyPrimitives:
+          -1,
+          false,
+          3,
+          3.14,
+          // For varCallback
+          7.toJInteger(),
+        );
+        final voidCallback = await voidCallbackResult.future;
+        expect(voidCallback.toDartString(deleteOriginal: true), 'hellohello');
+
+        final varCallback = await varCallbackResult.future;
+        expect(varCallback.intValue(), 14);
+
+        final manyPrimitives = await manyPrimitivesResult.future;
+        expect(manyPrimitives, -1 + 3 + 3.14.toInt() + 1);
+
+        myInterface.delete();
+      });
+    }
+  });
+
   group('$groupName (load tests)', () {
     const k4 = 4 * 1024; // This is a round number, unlike say 4000
     const k256 = 256 * 1024;
diff --git a/pkgs/jnigen/test/test_util/bindings_test_setup.dart b/pkgs/jnigen/test/test_util/bindings_test_setup.dart
index b4d292cbd..c493ad144 100644
--- a/pkgs/jnigen/test/test_util/bindings_test_setup.dart
+++ b/pkgs/jnigen/test/test_util/bindings_test_setup.dart
@@ -19,7 +19,7 @@ import 'test_util.dart';
 final simplePackageTest = join('test', 'simple_package_test');
 final jacksonCoreTest = join('test', 'jackson_core_test');
 final kotlinTest = join('test', 'kotlin_test');
-final jniJar = join(kotlinTest, 'jni.jar');
+final jniJar = join('build', 'jni_libs', 'jni.jar');
 
 final simplePackageTestJava = join(simplePackageTest, 'java');
 final kotlinTestKotlin = join(kotlinTest, 'kotlin');