Question

I can’t help but think that there is a very easy solution but no luck so far.
I think I’ve gone to the edge of the internet and back looking, read the whole RFC6455 to understand what’s going on behind scenes, etc.
I use eclipse for development and have the latest tomcat running on development machine.

This is my test class that eclipse won’t even compile because it suggests that I need to remove the @Override on the protected StreamInbound method. The actual wording:

The method createWebSocketInbound(String) of type wsListenerTest must override or implement a supertype method;

and it recommends removing the @Override.

I am trying to do everything native to Tomcat without any other servers or plugins.

Thanks in advance

package com.blah.blah;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.catalina.websocket.MessageInbound;
import org.apache.catalina.websocket.StreamInbound;
import org.apache.catalina.websocket.WebSocketServlet;
import org.apache.catalina.websocket.WsOutbound;


public class wsListenerTest extends WebSocketServlet {

private static final long serialVersionUID = 1L;
static int numConnections = 0;

    private static final String GUEST_PREFIX = "Guest";

    private final AtomicInteger connectionIds = new AtomicInteger(0);
    private final Set<ChatMessageInbound> connections = new CopyOnWriteArraySet<ChatMessageInbound>();

    @Override
    protected StreamInbound createWebSocketInbound(String subProtocol) {
        return new ChatMessageInbound(connectionIds.incrementAndGet());
    }

    private final class ChatMessageInbound extends MessageInbound {

        private final String nickname;

        private ChatMessageInbound(int id) {
            this.nickname = GUEST_PREFIX + id;
        }

        @Override
        protected void onOpen(WsOutbound outbound) {
            connections.add(this);
            String message = String.format("* %s %s",
                    nickname, "has joined.");
            broadcast(message);
        }

        @Override
        protected void onClose(int status) {
            connections.remove(this);
            String message = String.format("* %s %s",
                    nickname, "has disconnected.");
            broadcast(message);
        }

        @Override
        protected void onBinaryMessage(ByteBuffer message) throws IOException {
            throw new UnsupportedOperationException(
                    "Binary message not supported.");
        }

        @Override
        protected void onTextMessage(CharBuffer message) throws IOException {
            // Never trust the client
//                String filteredMessage = String.format("%s: %s",nickname, HTMLFilter.filter(message.toString()));
            broadcast(message.toString());
        }

        private void broadcast(String message) {
            for (ChatMessageInbound connection : connections) {
                try {
                    CharBuffer buffer = CharBuffer.wrap(message);
                    connection.getWsOutbound().writeTextMessage(buffer);
                } catch (IOException ignore) {
                    // Ignore
                }
            }
        }
    }
}   

Answer 1

I think the compiler is complaining about this @Override because the WebSocketServlet’s createWebSocketInbound() method has the following

protected abstract StreamInbound createWebSocketInbound(String subProtocol,
                                                        HttpServletRequest request);

Try adding the HttpServletRequest parameter to your method and that should help to get you past this roadblock.