TomcatWebSocketTest TestWebSocketServlet.java

package test;

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 javax.servlet.http.HttpServletRequest;

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

/**
 * Tested with Tomcat 7.0.42
 *
 */
public class TestWebSocketServlet extends WebSocketServlet {

    private static final long serialVersionUID = -7663708549630020769L;

    // for message that will be sent to client
    private final AtomicInteger _cnt = new AtomicInteger(0);
    // hold each connection in this Set
    private final Set<TestMessageInbound> connections =
        new CopyOnWriteArraySet<TestMessageInbound>();
    /**
     * For create connection only, each connection will
     * handle it self as needed
     */
    @Override
    protected StreamInbound createWebSocketInbound(String subProtocol,
            HttpServletRequest request) {
        /* enable this fragment to send message by server directly
         *
        if (_cnt.getAndIncrement() == 0) {
            new Thread(new Runnable(){
                public void run () {
                    try{
                        while (true) {
                            send();
                            Thread.sleep(1000);
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }).start();
        }
        */
        return new TestMessageInbound();
    }
    private final class TestMessageInbound extends MessageInbound {
        // add self instance into connections Set while opened
        @Override
        protected void onOpen(WsOutbound outbound) {
            connections.add(this);
        }
        // remove self instance from connections Set whild closed
        @Override
        protected void onClose(int status) {
            connections.remove(this);
        }
        // ignore binary message since we just want to process text messages
        @Override
        protected void onBinaryMessage(ByteBuffer message) throws IOException {
            throw new UnsupportedOperationException(
                "Unsupported: Binary message.");
        }
        // send a message to each connection in connections Set
        // while receive a text message
        @Override
        protected void onTextMessage(CharBuffer message) throws IOException {
            send();
        }
    }
    public void send () {
        String msg = "Current count: " + _cnt.getAndIncrement();
        for (TestMessageInbound connection : connections) {
            try {
                connection.getWsOutbound().writeTextMessage(CharBuffer.wrap(msg));
            } catch (IOException ignore) {
                /* ignore */
            }
        }
    }
}