In java binding, how to know what Construct operator requires?

[linghengqian]

• I admit this is a naive question, but I don't seem to notice any documentation explaining this.
• In https://opendal.apache.org/docs/quickstart#demo-1 , there is code like this,

// Configure service
final Map<String, String> conf = new HashMap<>();
conf.put("root", "/tmp");
// Construct operator
final Operator op = Operator.of("fs", conf);
// Write data
op.write("hello.txt", "Hello, World!").join();
// Read data
final byte[] bs = op.read("hello.txt").join();
// Delete
op.delete("hello.txt").join();

• Of course, I certainly don't believe that OpenDAL's java binding only supports fs. But how do I know that fs requires a Map containing a key-value pair called root? Also, how do I know the name of the other filesystems besides Operator.of("fs", conf)?

• I assume the string for fs comes from the image below?

• 

• I see idea: Introduce Codegen into OpenDAL #4279 is not done yet. It sounds like the documentation needs to properly state that users of the Java binding need to be able to read Rust source code? Documents like https://vuejs.org/guide/introduction.html#what-is-vue require readers of Vue's documentation to know HTML, CSS, and JavaScript at specific URLs in advance. Does the Java binding documentation for OpenDAL also need to state the URL of the Rust documentation?

• 

[tisonkun]

Not the Rust source code, but the API docs: https://docs.rs/opendal/latest/opendal/services/index.html

For example, https://docs.rs/opendal/latest/opendal/services/struct.S3.html will tell you the options that can be used for constructing an S3 operator.

[linghengqian]

For example, https://docs.rs/opendal/latest/opendal/services/struct.S3.html will tell you the options that can be used for constructing an S3 operator.

• I quickly compared the differences between https://docs.rs/opendal/latest/opendal/services/struct.Fs.html and https://opendal.apache.org/docs/quickstart#java-binding . So Rust's functional programming code,

let mut builder = Fs::default()
        .root("/tmp");

• Corresponding to,

final Map<String, String> conf = new HashMap<>();
conf.put("root", "/tmp");
final Operator op = Operator.of("fs", conf);

• Similarly, https://docs.rs/opendal/latest/opendal/services/struct.S3.html#basic-setup ,

let mut builder = S3::default()
      .root("/path/to/dir")
      .bucket("test")
      .region("us-east-1")
      .endpoint("https://s3.amazonaws.com")
      .access_key_id("access_key_id")
      .secret_access_key("secret_access_key");

• Can it correspond to?

final Map<String, String> conf = new HashMap<>();
conf.put("root", "/path/to/dir");
conf.put("bucket", "test");
conf.put("region", "us-east-1");
conf.put("endpoint", "https://s3.amazonaws.com");
conf.put("access_key_id", "access_key_id");
conf.put("secret_access_key", "secret_access_key");
final Operator op = Operator.of("s3", conf);

• If this is a reasonable way to convert code across languages, it might be better to give some examples at https://opendal.apache.org/docs/binding-java .
• I must admit that I am actually a S3 novice, and Amazon China restricts individual developer account registration.

[Xuanwo]

Thank you @linghengqian for reporting this. This is an issue we are still working on. We have developed a new configuration system and will implement it for bindings so that all users can have a static list of available configuration values.

Until we have completed that, users may need to refer to the Rust documentation for the available configuration values. Apologies for the inconvenience.

[tisonkun]

Anyway we may improve the Java API docs. And I recently found some potentially additional options that cannot be directly mapped to Rust's config, like using a no_proxy client ..