在项目中，需要用websocket和其他服务器进行通信，而websocket是长连接，建立连接后，监听消息，然后进行消息的处理。也就是消息的异步处理。

使用java websocket需要实现的接口如下

	public abstract void onOpen( ServerHandshake handshakedata );
	public abstract void onMessage( String message );
	public abstract void onClose( int code, String reason, boolean remote );
	public abstract void onError( Exception ex );
	public void onMessage( ByteBuffer bytes ) {
	}
	public void onFragment( Framedata frame ) {
	}

对于习惯使用同步请求的java开发者来说，用起来还是不方便的。

参考网上资料，CountDownLatch把java的websocket请求从异步修改为同步，如下：

package cc.openwiki.model;

import lombok.extern.slf4j.Slf4j;
import org.java_websocket.client.WebSocketClient;
import org.java_websocket.handshake.ServerHandshake;

import java.net.URI;
import java.nio.ByteBuffer;
import java.util.concurrent.CountDownLatch;

/**
 * Created by admin on 2017/6/6.
 */
@Slf4j
public class WebSocketClientExt extends WebSocketClient {
    public WebSocketClientExt(URI serverURI){
        super(serverURI);
    }
    private Object lock = new Object();
    private Object result = null;

    private CountDownLatch downLatch = null;


    public Object sendOb(Object object){
        synchronized (lock){
            downLatch = new CountDownLatch(1);
            sendImpl(object);
            try {
                downLatch.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }finally {
                return result;
            }
        }
    }

    public void sendImpl( Object object ){
        if(object instanceof String){
            super.send((String)object);
        }else if(object instanceof byte[]){
            super.send((byte[])object);
        }

    }


    @Override
    public void onOpen(ServerHandshake handshakedata) {
        log.debug("open handshakedata。。。");
    }

    @Override
    public void onMessage(String message) {
        log.debug("receive message。。。");
        result = message;
        if(downLatch!=null){
            downLatch.countDown();
        }
    }

    public void onMessage( ByteBuffer bytes ) {
        log.debug("receive ByteBuffer message。。。");
        result = bytes;
        if(downLatch!=null){
            downLatch.countDown();
        }
    }

    @Override
    public void onClose(int code, String reason, boolean remote) {
        log.debug("close websocket 。。");
    }

    @Override
    public void onError(Exception ex) {
        log.debug("onError 。。");
    }
}

调用方式如下：

WebSocketClientExt webSocketClientExt = new WebSocketClientExt(uri);
try {
    webSocketClientExt.connectBlocking();
} catch (InterruptedException e) {
    log.info("connect excepiont {}", e);
}
Object result = webSocketClientExt.sendOb(data.toByteArray());

用起来是不是熟悉了 :)

by sim