How to initialize a WebSocket Endpoint with constructor parameters

Question

I am using javax.websocket.* API right now but I don't know how to initialize an Endpoint with some constructor parameters after searching on the Internet.

ServerContainer container = WebSocketServerContainerInitializer.configureContext(context); //jetty
container.addEndpoint(MyWebSocketEndpoint.class);

I want pass through some parameters when initializing MyWebSocketEndpoint then I can use the parameter, say clientQueue, in my onOpen method doing something like:

clientQueue.add(new Client(session));

Answer 1

You need to call ServerContainer.addEndpoint(ServerEndpointConfig) and need a ServerEndpointConfig.Configurator implementation to make this work.

First create a custom ServerEndpointConfig.Configurator class which acts as factory for your endpoint:

public class MyWebSocketEndpointConfigurator extends ServerEndpointConfig.Configurator {
    private ClientQueue clientQueue_;

    public MyWebSocketEndpoint(ClientQueue clientQueue) {
        clientQueue_ = clientQueue;
    }

    public <T> T getEndpointInstance(Class<T> clazz) throws InstantiationException {
        return (T)new MyWebSocketEndpoint(clientQueue_);
    }
}

and then register it on the ServerContainer:

ClientQueue clientQueue = ...
ServerContainer container = ...
container.addEndpoint(ServerEndpointConfig.Builder
    .create(MyWebSocketEndpoint.class, "/") // the endpoint url
    .configurator(new MyWebSocketEndpointConfigurator(clientQueue _))
    .build());