JSR-356 websocket - cannot get return code after stopping container

Question

I have built a client server application using javax websockets.Though JSR 356 doesn't have methods to stop websocket container, i managed to stop the container after casting to jetty Lifecyle.Once stopping the container i have wrote

system.exit(1);

But the return is code always zero from the client program.

code: @ClientEndpoint

    public boolean close()
        {
            try
              {
                  if(this.container != null && this.container instanceof LifeCycle) { 
                      logger.trace("stoping container...");
                      ((LifeCycle) this.container).stop();
                  }

                  this.session.close();
        
                return true;
            }
            catch (Exception e)
            {
                logger.trace("Exception occured while closing the connection",e);
                return false;
            }
        }

code : Invoking close method from another class

public closeConnection(){

     this.wc.close();
     System.exit(1);

}

Any help is appreciated :-)

Joakim Erdfelt · Accepted Answer · 2020-09-03T19:20:49.767

Are you attempting to call closeConnection or close from a thread that belongs to the container or the container's ThreadPool / Executor?

Also, once the container is stopped, all of the sessions will be stopped too.

Change @ClientEndpoint close() to be ...

public void close()
{
    try
    {
        this.session.close();
    }
    catch (Exception e)
    {
        logger.trace("Exception occured while closing the connection",e);
    }
}

And make closeConnection() simply ...

public closeConnection()
{
    LifeCycle.stop(this.wc.getContainer());
    System.exit(1);
}

A working example of this can be found at
https://github.com/joakime/javaxwebsocket-client-returncode

Which has the code ...

App.java

package org.eclipse.jetty.demo;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import javax.websocket.ClientEndpointConfig;
import javax.websocket.ContainerProvider;
import javax.websocket.DeploymentException;
import javax.websocket.WebSocketContainer;

import org.eclipse.jetty.util.component.LifeCycle;

public class App
{
    private static final App MAIN_INSTANCE = new App();

    private WebSocketContainer client;

    public static void main(String[] args) throws IOException, DeploymentException, URISyntaxException
    {
        App.MAIN_INSTANCE.connect();
    }

    public static void stop(int returnCode)
    {
        // Trigger stop from thread that does not belong to Container.
        new Thread(() ->
        {
            LifeCycle.stop(App.MAIN_INSTANCE.client);
            System.exit(returnCode);
        }).start();
    }

    private WebSocketContainer getClientContainer()
    {
        if (client == null)
            client = ContainerProvider.getWebSocketContainer();
        return client;
    }

    public void connect() throws IOException, DeploymentException, URISyntaxException
    {
        URI echoUri = URI.create("wss://echo.websocket.org");

        ClientEndpointConfig clientEndpointConfig = ClientEndpointConfig.Builder.create()
            .configurator(new OriginServerConfigurator(echoUri))
            .build();

        EchoEndpoint echoEndpoint = new EchoEndpoint();
        getClientContainer().connectToServer(echoEndpoint, clientEndpointConfig, echoUri);
        System.out.printf("Connected to : %s%n", echoUri);
    }
}

EchoEndpoint.java

package org.eclipse.jetty.demo;

import javax.websocket.CloseReason;
import javax.websocket.Endpoint;
import javax.websocket.EndpointConfig;
import javax.websocket.MessageHandler;
import javax.websocket.Session;

/**
 * Basic Echo Client Endpoint
 */
public class EchoEndpoint extends Endpoint implements MessageHandler.Whole<String>
{
    private Session session;

    @Override
    public void onClose(Session session, CloseReason closeReason)
    {
        System.out.printf("Connection closed: Session.id=%s - %s%n", session.getId(), closeReason);
        this.session = null;
    }

    @Override
    public void onOpen(Session session, EndpointConfig config)
    {
        System.out.printf("Got open: Session.id=%s%n", session.getId());
        this.session = session;
        this.session.addMessageHandler(this);
        try
        {
            session.getBasicRemote().sendText("Hello");
            session.getBasicRemote().sendText("How are things?");
            session.getBasicRemote().sendText("Thanks for the conversation.");
        }
        catch (Throwable t)
        {
            t.printStackTrace();
        }
    }

    @Override
    public void onMessage(String msg)
    {
        System.out.printf("Got msg: \"%s\"%n", msg);
        if (msg.contains("Thanks"))
        {
            App.stop(1);
        }
    }

    @Override
    public void onError(Session session, Throwable cause)
    {
        cause.printStackTrace();
    }
}

Thanks @Joakim Erdfelt but this didn't work. The thread is not belong to container's thread i think because consider i have my _@clientendpoint_ implementation in **class A** and from **class B** (program contains main method) i'm creating object of **class A** and eventually i'm creating container in **class A** constructor. — Logesh Elangovan, Sep 03 '20 at 12:28
It works. trust me. :-) I've updated the answer, and even linked to an example project that does it. — Joakim Erdfelt, Sep 03 '20 at 15:39
That was a lit @Joakim Erdfelt. But here ` new Thread(() -> { LifeCycle.stop(App.MAIN_INSTANCE.client); System.exit(returnCode); }).start();` the only difference is stopping container in new thread. Any reason specific reason behind this? — Logesh Elangovan, Sep 03 '20 at 16:52
The reason is as stated in the answer, you cannot stop the LifeCycle from a thread that is being managed by that LifeCycle. This just ensures that the container stop occurs in a different thread. Since the example app shows it stopping during a onMessage receive, I know that is always in a thread managed by that container's LifeCycle. — Joakim Erdfelt, Sep 03 '20 at 17:36

JSR-356 websocket - cannot get return code after stopping container

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