Autobahn|Java

Client library providing WAMP on Java 8 (Netty) and Android, plus (secure) WebSocket for Android.

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Autobahn|Java is a subproject of the Autobahn project and provides open-source client implementations for

• The WebSocket Protocol
• The Web Application Messaging Protocol (WAMP)

running on Android and Netty/Java8/JVM.

The WebSocket layer is using a callback based user API, and is specifically written for Android. Eg it does not run any network stuff on the main (UI) thread.

The WAMP layer is using Java 8 CompletableFuture for WAMP actions (call, register, publish and subscribe) and the Observer pattern for WAMP session, subscription and registration lifecycle events.

The library is MIT licensed, maintained by the Crossbar.io Project, tested using the AutobahnTestsuite and published as a JAR to Maven and as a Docker toolchain image to Dockerhub.

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Getting Started

The demo clients are easy to run, you only need make and docker installed to get things rolling.

$ make crossbar # Starts crossbar in a docker container
$ make python # Starts a python based WAMP components that provides calls for the Java demo client

and finally

$ make java # Starts the java (Netty) based demo client that performs WAMP actions

Show me some code

The code in demo-gallery contains some examples on how to use the autobahn library, it also contains convenience methods to use. Below is a basic set of code examples showing all 4 WAMP actions.

Subscribe to a topic

public void demonstrateSubscribe(Session session, SessionDetails details) {
    // Subscribe to topic to receive its events.
    CompletableFuture<Subscription> subFuture = session.subscribe("com.myapp.hello",
            this::onEvent);
    subFuture.whenComplete((subscription, throwable) -> {
        if (throwable != null) {
            // We have successfully subscribed.
            System.out.println("Subscribed to topic " + subscription.topic);
        } else {
            // Something went bad.
            throwable.printStackTrace();
        }
    });
}

private void onEvent(List<Object> args, Map<String, Object> kwargs, EventDetails details) {
    System.out.println(String.format("Got event: %s", args.get(0)));
}

Since we are only accessing args in onEvent(), we could simplify it like:

private void onEvent(List<Object> args) {
    System.out.println(String.format("Got event: %s", args.get(0)));
}

Publish to a topic

public void demonstratePublish(Session session, SessionDetails details) {
    // Publish to a topic that takes a single arguments
    List<Object> args = Arrays.asList("Hello World!", 900, "UNIQUE");
    CompletableFuture<Publication> pubFuture = session.publish("com.myapp.hello", args);
    pubFuture.thenAccept(publication -> System.out.println("Published successfully"));
    // Shows we can separate out exception handling
    pubFuture.exceptionally(throwable -> {
        throwable.printStackTrace();
        return null;
    });
}

A simpler call would look like:

public void demonstratePublish(Session session, SessionDetails details) {
    CompletableFuture<Publication> pubFuture = session.publish("com.myapp.hello", "Hi!");
    ...
}

Register a procedure

public void demonstrateRegister(Session session, SessionDetails details) {
    // Register a procedure.
    CompletableFuture<Registration> regFuture = session.register("com.myapp.add2", this::add2);
    regFuture.thenAccept(registration ->
            System.out.println("Successfully registered procedure: " + registration.procedure));
}

private CompletableFuture<InvocationResult> add2(
        List<Object> args, Map<String, Object> kwargs, InvocationDetails details) {
    int res = (int) args.get(0) + (int) args.get(1);
    List<Object> arr = new ArrayList<>();
    arr.add(res);
    return CompletableFuture.completedFuture(new InvocationResult(arr));
}

A very precise add2 may look like:

private List<Object> add2(List<Integer> args, InvocationDetails details) {
    int res = args.get(0) + args.get(1);
    return Arrays.asList(res, details.session.getID(), "Java");
}

Call a procedure

public void demonstrateCall(Session session, SessionDetails details) {
    // Call a remote procedure.
    CompletableFuture<CallResult> callFuture = session.call("com.myapp.add2", 10, 20);
    callFuture.thenAccept(callResult ->
            System.out.println(String.format("Call result: %s", callResult.results.get(0))));
}

Connecting the dots

public void main() {
    // Create a session object
    Session session = new Session();
    // Add all onJoin listeners
    session.addOnJoinListener(this::demonstrateSubscribe);
    session.addOnJoinListener(this::demonstratePublish);
    session.addOnJoinListener(this::demonstrateCall);
    session.addOnJoinListener(this::demonstrateRegister);

    // finally, provide everything to a Client and connect
    Client client = new Client(session, url, realm);
    CompletableFuture<ExitInfo> exitInfoCompletableFuture = client.connect();
}

WebSocket on Android

TBD

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Get in touch

Get in touch on IRC #autobahn on chat.freenode.net or join the mailing list.

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Version 1

Version 1 of this library is still in the repo here, but is no longer maintained.

Version 1 only supported non-secure WebSocket on Android and only supported WAMP v1.

Both of these issues are fixed in the (current) version of Autobahn|Java.

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