Support java.apply.workspaceEdit

Fixes issue#376
This follows exactly same pattern as organizeImports was done.
This should preserve existing behaviour for vscode

org.eclipse.jdt.ls.core/plugin.xml

@@ -55,6 +55,9 @@
             <command
                   id="java.edit.organizeImports">
             </command>
+            <command
+                  id="java.apply.workspaceEdit">
+            </command>
             <command
                   id="java.edit.stringFormatting">
             </command>

org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/JDTDelegateCommandHandler.java

@@ -70,6 +70,23 @@ public Object executeCommand(String commandId, List<Object> arguments, IProgress
 						// workspaceEdit on the custom command.
 						return result;
 					}
+				case "java.apply.workspaceEdit":
+					final WorkspaceEdit r = (WorkspaceEdit) JSONUtility.toLsp4jModel(arguments.get(0), WorkspaceEdit.class);
+
+					if (JavaLanguageServerPlugin.getPreferencesManager().getClientPreferences()
+							.isWorkspaceApplyEditSupported()) {
+						JavaLanguageServerPlugin.getInstance().getClientConnection()
+								.applyWorkspaceEdit((WorkspaceEdit) r);
+						// return an empty object to avoid errors on client
+						return new Object();
+					} else {
+						// we are returning a workspace edit here in order to accomodate the clients
+						// that
+						// did not implement workspace/applyEdit from LSP. This still allows them to
+						// implement applying
+						// workspaceEdit on the custom command.
+						return r;
+					}
 				case "java.edit.stringFormatting":
 					FormatterHandler handler = new FormatterHandler(JavaLanguageServerPlugin.getPreferencesManager());
 					return handler.stringFormatting((String) arguments.get(0), JSONUtility.toModel(arguments.get(1), Map.class), Integer.parseInt((String) arguments.get(2)), monitor);

org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/JSONUtility.java

@@ -14,6 +14,7 @@
 package org.eclipse.jdt.ls.core.internal;
 
 import java.util.HashMap;
+import java.util.Map;
 
 import org.eclipse.lsp4j.jsonrpc.json.MessageJsonHandler;
 
@@ -61,6 +62,9 @@ private static <T> T toModel(Gson gson, Object object, Class<T> clazz) {
 		if (object instanceof String json) {
 			return gson.fromJson(json, clazz);
 		}
+		if (object instanceof Map map) {
+			return gson.fromJson(gson.toJsonTree(map), clazz);
+		}
 		return null;
 	}
 }