Using Guice with Java WebSockets (JSR-356)

Configuration to get Guice injection on Websocket endpoints

First, we need a custom endpoint builder.

public class WSConfigurator extends ServerEndpointConfig.Configurator {  
  @Inject
  private static Injector injector;

  @Override
  public <T> T getEndpointInstance(Class<T> endpointClass)
          throws InstantiationException
  {
    return injector.getInstance(endpointClass);
  }
}

We need to bootstrap the injector in the above configurator from one of our Guice modules.

public class WebSocketModule extends AbstractModule {  
  @Override
  protected void configure() {
    requestStaticInjection(WSConfigurator.class);
  }
}

Finally, we can use @Inject on the endpoints’ constructor.

@ServerEndpoint(
        value = "/ws/sync",

       configurator = WSConfigurator.class)
public class WSSync extends AsyncWebSocketServer {  
  @Inject
  public WSSync(EventBus eventBus) {
    ...
  }
}