【netty】java如何作为websocket客户端 对服务端发起请求

是的 本文介绍java如何作为客户端 发起websocket请求
博主不做标题党 不会服务端客户端分不清就写个标题 乱写文章

前言

为什么会使用java作为websocket客户端？ 虽说websocket协议 本意是web与服务端之间的通讯协议，那假设有一天 我们的供应商 或者是甲方大爷 只提供了websocket接口呢？
如果直接让前端去对接，再把数据传给后端，那从前端对接到后端入库的步骤，万一出现数据丢失呢？ 总之把数据处理放在后端，是相对可靠的， 我们可以借助netty来实现websocket客户端功能

长链接有两点值得注意的，一是心跳机制 二是重连机制
如果不发送心跳包，可能过会儿连接就断开了；
重新机制就比较好理解了，不管是服务端还是客户端的断开，作为客户端都需要能够重连

代码

博主对长链接并不是特别熟练，但是什么代码是能正式用的，什么代码上不了生产只是个写着玩的demo 还是一眼能分辨出来的，代码主要参考 [email protected]:yimiancheng/netty-study.git ，写的很不错，代码优化空间很少了， 线程池博主是推荐用new ThreadPoolExecutor()创建，避免OOM的问题，除此之外应该是准生产环境级别代码了。

maven依赖

          <dependency>
               <groupId>io.nettygroupId>
               <artifactId>netty-allartifactId>
               <version>4.1.35.Finalversion>
           dependency>

websocket客户端handle类 主要处理接收的消息、事件等，
事件触发会进入userEventTriggered方法
建立连接会进入channelActive方法
接收消息会进入channelRead0方法
出现异常会进入exceptionCaught方法
断开连接会进入channelInactive方法（本文中未重写该方法， 在channelInactive方法中重连也是没问题的）

import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.SocketClient;
import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.websocket.SendMsg;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.PingWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketClientProtocolHandler;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.timeout.IdleStateEvent;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * WebSocketClientFrameHandler
 *
 * @date 2019/8/20 16:42
 */
public class WebSocketClientFrameHandler extends SimpleChannelInboundHandler<WebSocketFrame> {
    private static final Logger LOG = LoggerFactory.getLogger(WebSocketClientFrameHandler.class);
    private SocketClient socketClient;
    private ChannelPromise channelPromise;

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        LOG.info("客户端接收到事件 " + (evt.getClass()) + " | " + evt.toString());

        if(WebSocketClientProtocolHandler.ClientHandshakeStateEvent.HANDSHAKE_COMPLETE.equals(evt)) {
            LOG.info(ctx.channel().id().asShortText() + " 握手完成！");
            socketClient.CHANNEL_IS_READY.set(true);
            channelPromise.setSuccess();
            // SendMsg.send(ctx.channel(),"客户端握手完成消息 -》服务器时间: " + System.currentTimeMillis());
        }
        else if(evt instanceof IdleStateEvent){
            //ctx.channel().writeAndFlush(new PingWebSocketFrame());
            IdleStateEvent evtIdle = (IdleStateEvent) evt;
            switch(evtIdle.state()) {
                case WRITER_IDLE:
                    // SendMsg.send(ctx.channel(),"客户端 ping 消息 -》服务器时间: " + System.currentTimeMillis());
                    ctx.channel().writeAndFlush(new PingWebSocketFrame());
                case READER_IDLE:
                    // SendMsg.send(ctx.channel(),"客户端 ping 消息 -》服务器时间: " + System.currentTimeMillis());
                    ctx.channel().writeAndFlush(new PingWebSocketFrame());
                default:
                    break;
            }
        }

        super.userEventTriggered(ctx, evt);
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        LOG.info("打开连接 handlerAdded SUCCESS. | name = " +channel.id().asShortText());
        super.handlerAdded(ctx);
        channelPromise = ctx.newPromise();
    }

    /**
     * Channel 已经被注册到了EventLoop
     */
    @Override
    public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        LOG.info("注册成功 channelRegistered SUCCESS. | name = " +channel.id().asShortText());
        super.channelRegistered(ctx);
    }

    /**
     * Channel 处于活动状态（已经连接到它的远程节点）。它现在可以接收和发送数据了
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        LOG.info("活动状态 channelActive SUCCESS. | name = " +channel.id().asShortText());
        super.channelActive(ctx);
    }

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, WebSocketFrame webSocketFrame) throws
        Exception {
        if(webSocketFrame instanceof TextWebSocketFrame) {
            // String message = textWebSocketFrame.content().toString(Charset.forName("utf-8"));
            String message = ((TextWebSocketFrame) webSocketFrame).text();
            LOG.info("客户端接收到消息：" + message);
        }
        else {
            LOG.info("接收到消息类型" + (webSocketFrame.getClass().getName()));
        }

        SendMsg.sendPong(channelHandlerContext.channel());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        LOG.error("消息处理失败: " + cause.getMessage(), cause);
        ctx.close();
    }

    /**
     * Channel 已经被创建，但还未注册到EventLoop
     * 连接断开
     */
    @Override
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        LOG.info("连接断开 channelUnregistered SUCCESS. | name = " +channel.id().asShortText());
        super.channelUnregistered(ctx);
        channelPromise = null;
    }

    public SocketClient getSocketClient() {
        return socketClient;
    }

    public void setSocketClient(SocketClient socketClient) {
        this.socketClient = socketClient;
    }

    public ChannelPromise getChannelPromise() {
        return channelPromise;
    }
}

心跳任务类

import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.SocketClient;
import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.websocket.SendMsg;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.TimerTask;

/**
 * HeartBeatTimerTask
 *
 * @date 2019/9/2 16:24
 */
public class HeartBeatTimerTask extends TimerTask {
    private static final Logger LOG = LoggerFactory.getLogger(ReconnectTimerTask.class);
    private SocketClient socketClient;

    public HeartBeatTimerTask(SocketClient socketClient) {
        this.socketClient = socketClient;
    }

    @Override
    public void run() {
        if(socketClient != null && socketClient.isValid()) {
            SendMsg.send(socketClient.getChannel(), "客户端心跳消息 => " + System.currentTimeMillis());
        }
    }
}

重连任务类

import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.SocketClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.TimerTask;

/**
 * ReconnectTimerTask
 *
 * @date 2019/9/2 16:03
 */
public class ReconnectTimerTask extends TimerTask {
    private static final Logger LOG = LoggerFactory.getLogger(ReconnectTimerTask.class);
    private SocketClient socketClient;

    public ReconnectTimerTask(SocketClient socketClient) {
        this.socketClient = socketClient;
    }

    @Override
    public void run() {
        if(socketClient != null && !socketClient.isValid()) {
            LOG.info("=== 客户端重连 " + System.currentTimeMillis());
            socketClient.connect();
        }
    }
}

自定义线程工厂类，主要是给线程重命名 便于维护、调试

import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;

public class NamedThreadFactory implements ThreadFactory {
    static final AtomicInteger poolNumber = new AtomicInteger(1);
    final AtomicInteger threadNumber = new AtomicInteger(1);
    final ThreadGroup group;
    final String prefix;
    final boolean isDaemon;
    final int priority;

    public NamedThreadFactory() {
        this("pool");
    }

    public NamedThreadFactory(String prefix) {
        this(prefix, false, Thread.NORM_PRIORITY);
    }

    public NamedThreadFactory(String prefix, boolean isDaemon, int priority) {
        SecurityManager sm = System.getSecurityManager();
        this.group = (sm != null) ? sm.getThreadGroup() : Thread.currentThread().getThreadGroup();
        this.prefix = prefix + "-" + poolNumber.getAndIncrement() + "-thread-";
        this.isDaemon = isDaemon;
        this.priority = priority;
    }

    public Thread newThread(Runnable r) {
        Thread thread = new Thread(group, r, prefix + threadNumber.getAndIncrement(), 0);
        thread.setDaemon(isDaemon);
        thread.setPriority(priority);
        return thread;
    }
}

消息监听类，主要用于发送消息（包括心跳包）是否成功

import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

class CustomerChannelFutureListener implements ChannelFutureListener {
    private static final Logger LOG = LoggerFactory.getLogger(CustomerChannelFutureListener.class);

        public void operationComplete(ChannelFuture channelFuture) throws Exception {
            // LOG.info(JSON.toJSONString(channelFuture));
            if(channelFuture.isDone() && channelFuture.isSuccess()){
               // LOG.info("send success.");
            }
            else {
                channelFuture.channel().close();
                LOG.info("send error. cause = " + channelFuture.cause());
                channelFuture.cause().printStackTrace();
            }
        }
    }

简单封装的消息发送类

import com.alibaba.fastjson.JSON;
import io.netty.channel.Channel;
import io.netty.handler.codec.http.websocketx.PingWebSocketFrame;
import io.netty.handler.codec.http.websocketx.PongWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import org.apache.commons.collections.MapUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Collections;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * SendMsg
 *
 * @date 2019/8/30 18:02
 */
public class SendMsg {
    private static final Logger LOG = LoggerFactory.getLogger(SendMsg.class);
    public static ConcurrentHashMap<String, Channel> ALL_CHANNEL = new ConcurrentHashMap<String, Channel>();

    public static void startSendMsg() {
        Thread thread = new Thread(new Runnable() {
            public void run() {
                while(true) {
                    sendMsgTest();
                }
            }
        });

        thread.start();
    }

    public static void sendMsgTest() {
        try {
            Map<String, Channel> map = Collections.unmodifiableMap(ALL_CHANNEL);
            LOG.info("map size = " + map.size());
            if(MapUtils.isEmpty(map)) {
                Thread.sleep(2000);
                return;
            }

            for(Map.Entry<String, Channel> entry : map.entrySet()) {
                LOG.info("------------- key = " + entry.getKey());
                send(entry.getValue(), "服务端发送消息 " + entry.getKey() + " | " + System.currentTimeMillis());
            }

            Thread.sleep(10000);
        }
        catch(Exception ex) {
            ex.printStackTrace();
        }
    }

    public static void put(Channel channel) {
        ALL_CHANNEL.put(channel.id().asShortText(), channel);
    }

    public static void remove(Channel channel) {
        ALL_CHANNEL.remove(channel.id().asShortText());
    }

    public static void send(Channel channel, Object msg) {
        final String textMsg = JSON.toJSONString(msg);

        if(channel != null && channel.isActive()) {
            TextWebSocketFrame frame = new TextWebSocketFrame(textMsg);
            channel.writeAndFlush(frame)
                .addListener(new CustomerChannelFutureListener());
        }
        else {
            LOG.error("消息发送失败！ textMsg = " + textMsg);
        }
    }

    public static void sendPing(Channel channel) {
        if(channel != null && channel.isActive()) {
            channel.writeAndFlush(new PingWebSocketFrame())
                .addListener(new CustomerChannelFutureListener());
        }
        else {
            LOG.error("消息发送失败！ ping");
        }
    }

    public static void sendPong(Channel channel) {
        if(channel != null && channel.isActive()) {
            channel.writeAndFlush(new PongWebSocketFrame())
                .addListener(new CustomerChannelFutureListener());
        }
        else {
            LOG.error("消息发送失败！ pong");
        }
    }

}

channel初始化

import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.handler.WebSocketClientFrameHandler;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketClientProtocolHandler;
import io.netty.handler.timeout.IdleStateHandler;

/**
 * ClientChannelInitializer
 *
 * @date 2019/8/31 16:05
 */
public class ClientChannelInitializer extends ChannelInitializer<SocketChannel> {
    private WebSocketClientHandshaker webSocketClientHandshaker;
    private WebSocketClientFrameHandler webSocketFrameHandler;

    public ClientChannelInitializer(WebSocketClientHandshaker webSocketClientHandshaker, WebSocketClientFrameHandler
        webSocketFrameHandler) {
        this.webSocketClientHandshaker = webSocketClientHandshaker;
        this.webSocketFrameHandler = webSocketFrameHandler;
    }

    @Override
    protected void initChannel(SocketChannel socketChannel) throws Exception {
        ChannelPipeline pipeline = socketChannel.pipeline();

        pipeline.addLast(new HttpClientCodec());//Http协议编码解码器
        pipeline.addLast(new HttpObjectAggregator(65536));//聚合 HttpRequest
        pipeline.addLast(new IdleStateHandler(5, 10, 0));
        //会处理ping pong close消息
        pipeline.addLast(new WebSocketClientProtocolHandler(webSocketClientHandshaker,true));
        pipeline.addLast(webSocketFrameHandler);
    }
}

客户端主类 : 添加工作组 , 启动websocket client , 建立连接等

import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.handler.WebSocketClientFrameHandler;
import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.task.HeartBeatTimerTask;
import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.task.ReconnectTimerTask;
import com.qiuhuanhen.springroot.interfaces.websocket.websocketclient.thread.NamedThreadFactory;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelOption;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.DefaultHttpHeaders;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshakerFactory;
import io.netty.handler.codec.http.websocketx.WebSocketVersion;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.URI;
import java.net.URISyntaxException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * SocketClient
 *
 * @date 2019/8/20 17:53
 */
public class SocketClient {
    private static final Logger LOG = LoggerFactory.getLogger(SocketClient.class);

    public static String CLIENT_VERSION = "client_version";
    private static final int DEFAULT_PORT = 80;
    /**
     * 长链重连间隔时间，单位s
     */
    public static long RECONNECT_INTERVAL = 10;
    /**
     * 长链心跳时间，单位s
     */
    public static long FETCH_PERIOD = 30;

    public static String host = "127.0.0.1";
    public static int port = 8585;

    private Channel channel = null;
    private NioEventLoopGroup nioEventLoopGroup;

    public AtomicBoolean CHANNEL_IS_READY = new AtomicBoolean(false);

    private ScheduledExecutorService RECONNECT_TIMER;
    private ScheduledExecutorService HEARTBEAT_TIMER;
    static final String URL = System.getProperty("url", "ws://127.0.0.1:8585/boot/imserver/1111");
    URI uri = new URI(URL);

    static {
        // RECONNECT_TIMER = Executors.newSingleThreadScheduledExecutor();
    }


    public SocketClient(URI uri) throws URISyntaxException {
        this.uri = uri;
    }

    private void start() {
        Bootstrap boot = new Bootstrap();
        nioEventLoopGroup = new NioEventLoopGroup(Runtime.getRuntime().availableProcessors());

        try {
            HttpHeaders httpHeaders = new DefaultHttpHeaders();
            httpHeaders.add(CLIENT_VERSION, 1);

            WebSocketClientHandshaker webSocketClientHandshaker = WebSocketClientHandshakerFactory.newHandshaker(uri,
                WebSocketVersion.V13, null, false, httpHeaders);

            boot.group(nioEventLoopGroup)
                .option(ChannelOption.TCP_NODELAY, true)
                .channel(NioSocketChannel.class);

            WebSocketClientFrameHandler webSocketFrameHandler = new WebSocketClientFrameHandler();
            webSocketFrameHandler.setSocketClient(this);

            ClientChannelInitializer clientChannelInitializer =
                new ClientChannelInitializer(webSocketClientHandshaker, webSocketFrameHandler);

            boot.handler(new LoggingHandler(LogLevel.INFO));
            boot.handler(clientChannelInitializer);

            port = (uri.getPort() == -1) ? DEFAULT_PORT : uri.getPort();
            host = uri.getHost();
            channel = boot.connect(host, port).sync().channel();
            LOG.info("SocketClient has started. CHANNEL_IS_READY = " + CHANNEL_IS_READY.get());
            webSocketFrameHandler.getChannelPromise().sync();
            LOG.info("SocketClient has started full. CHANNEL_IS_READY = " + CHANNEL_IS_READY.get());
        }
        catch(Exception ex) {
            ex.printStackTrace();
            LOG.error("connect error. uri " + uri.toString());
        }
        finally {
            // nioEventLoopGroup.shutdownGracefully();
        }
    }

    /**
     * 客户端连接服务端
     */
    public void connect() {
        stop();
        start();
        startReconnect();
        doHeartBeat();
    }

    /**
     * 开启线程-断开重连
     */
    public void startReconnect() {
        RECONNECT_TIMER = new ScheduledThreadPoolExecutor(1,
            new NamedThreadFactory("reconnect-schedule-pool", Boolean.TRUE, Thread.NORM_PRIORITY));

        // https://www.jianshu.com/p/502f9952c09b
        RECONNECT_TIMER.scheduleAtFixedRate(new ReconnectTimerTask(this),
            RECONNECT_INTERVAL * 1000L, RECONNECT_INTERVAL * 1000L, TimeUnit.MILLISECONDS);
    }

    /**
     * 心跳
     */
    private void doHeartBeat() {
        HEARTBEAT_TIMER = new ScheduledThreadPoolExecutor(1,
            new NamedThreadFactory("heartbeat-schedule-pool", Boolean.TRUE, Thread.NORM_PRIORITY));

        // https://www.jianshu.com/p/502f9952c09b
        HEARTBEAT_TIMER.scheduleAtFixedRate(new HeartBeatTimerTask(this),
            FETCH_PERIOD * 1000L, FETCH_PERIOD * 1000L, TimeUnit.MILLISECONDS);
    }

    /**
     * 客户端停止
     */
    public void stop() {
        try {
            if(nioEventLoopGroup != null) {
                nioEventLoopGroup.shutdownGracefully();
            }

            if(channel != null) {
                channel.close();
            }

            if(RECONNECT_TIMER != null) {
                RECONNECT_TIMER.shutdown();
                RECONNECT_TIMER = null;
            }

            if(HEARTBEAT_TIMER != null) {
                HEARTBEAT_TIMER.shutdown();
                HEARTBEAT_TIMER = null;
            }
        }
        catch(Exception ex) {
            //do nothing.
        }
    }


    public boolean isValid() {
        if (channel != null && channel.isActive()) {
            return true;
        } else {
            return false;
        }
    }

    public Channel getChannel() {
        return channel;
    }

    public static void main(String[] args) {
        try {
            new SocketClient(new URI(URL)).connect();
        } catch (URISyntaxException e) {
            e.printStackTrace();
        }
    }
}

重连成功截图：