你敢信？就是这个 Netty 的网络框架差点把我整疯了，哭 jj

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发布于: 2020 年 12 月 09 日
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不知道大家对下面的这个图标眼熟不
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对，这就是netty，最近差点整疯了我的一个网络框架，下方是官网对他的描述，感兴趣大家可以去官网看一下，这不是今天的重点，接着往下看：
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为啥说这玩意快把我整疯了啊，哎，好奇害死猫啊，我这人是对网络一窍不通，所以网络的东西我一般是不去触碰的，但是，最近公司的人以及各大论坛里面，netty这个技术真的是如日中天，我身边的朋友去面试的回来也说这个技术问的有点多啊，我好奇心作怪就想去试一下，然后在网上查找了很多资料和代码实现，我就觉得没啥，于是自己搭建了一下玩玩，比方说下面我要跟大家说的这个重点：netty+springboot实现 长连接 - 心跳 - 自动重连 - 通信
然后出问题了，我作为程序员的执拗，不能有bug，这就出问题了，我们先来看一下网上的源码
package com.gzky.study;
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import com.gzky.study.netty.MsgPckDecode;
import com.gzky.study.netty.MsgPckEncode;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.timeout.IdleStateHandler;
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import java.util.Scanner;
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/**
 * @author biws
 * @date 2020/11/20
 **/
public class TestFor {
    private static NioEventLoopGroup worker = new NioEventLoopGroup();
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    private static Channel channel;
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    private static Bootstrap bootstrap;
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    boolean flag = true;
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    public static void main(String[] args) {
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        for (int i = 0; i < 30; i++) {
            long start = System.currentTimeMillis();
            Scanner sc= new Scanner(System.in);
            long end = System.currentTimeMillis();
            long l1 = end - start;
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            long start2 = System.currentTimeMillis();
            start();
            long end2 = System.currentTimeMillis();
            long l2 = end2 - start2;
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            if (l1 > l2) {
                System.out.println("Scanner大，false");
            } else {
                System.out.println("true--------------");
            }
        }
    }
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    private static void start() {
        bootstrap = new Bootstrap();
        bootstrap.group(worker)
                .channel(NioSocketChannel.class)
                .option(ChannelOption.TCP_NODELAY, true)
                .handler(new ChannelInitializer<Channel>() {
                    @Override
                    protected void initChannel(Channel ch) throws Exception {
                        // TODO Auto-generated method stub
                        ChannelPipeline pipeline = ch.pipeline();
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                        pipeline.addLast(new IdleStateHandler(3, 3, 5));
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                        pipeline.addLast(new MsgPckDecode());
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                        pipeline.addLast(new MsgPckEncode());
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                    }
                });
        doConnect();
    }
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    protected static void doConnect() {
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        if (channel != null && channel.isActive()) {
            return;
        }
        ChannelFuture connect = bootstrap.connect("127.0.0.1", 8089);
        //实现监听通道连接的方法
        connect.addListener(new ChannelFutureListener() {
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            @Override
            public void operationComplete(ChannelFuture channelFuture) throws Exception {
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                if (channelFuture.isSuccess()) {
                    channel = channelFuture.channel();
                    System.out.println("连接成功");
                }
            }
        });
    }
}
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好了，到这里，没问题，成功实现，我就觉得这也没啥啊，这不是挺简单的嘛，难道说他们是在面试的时候问道底层源码啊，这玩意整不了 啊，可能这就是命啊，我就没关，让他执行着，喝口饮料休息一下，没想到突然就报错了，然后又好了，emmmm，这不是自己给自己找事啊
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通过测试，模拟30次大约有3次失败的样子，回看源码，其实代码中存在的矛盾不难发现，就是Scanner和Channel谁的创建时间更短。可能在他的电脑上没有什么问题，但是在我这里就不行，感觉更像是在赌博，看你运气怎么样，这样那行啊，理工科的男孩子怎么能靠赌博呢？
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但是，咋整，我就在这一块就是一个渣渣啊，没办法，最后还是求助了公司的大神，幸好代码量不是特别大，抽了个周末的下午，俺俩一起在原有的代码基础上对客户端进行可以定程度的改造，现在所有的功能都已经实现，下面附上改进后的代码，有需要的朋友可以自己动手实现一下
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还是建议实现一下，毕竟可能我这里可以了，但是在你的pc端又会有其他的而不一样的问题，当然了，要是有云服务器测试一下更 不错
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一、pom文件
<!-- 解码and编码器 -->
<!-- https://mvnrepository.com/artifact/org.msgpack/msgpack -->
<dependency>
    <groupId>org.msgpack</groupId>
    <artifactId>msgpack</artifactId>
    <version>0.6.12</version>
</dependency>
<!-- 引入netty依赖 -->
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.6.Final</version>
</dependency>
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二、配置项
package com.gzky.study.netty;
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/**
 * 配置项
 *
*
 * @author biws
 * @date 2020/11/20
 **/
public interface TypeData {
    //客户端代码
    byte PING = 1;
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    //服务端代码
    byte PONG = 2;
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    //顾客
    byte CUSTOMER = 3;
}
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三、消息类型分离器
package com.gzky.study.netty;
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import org.msgpack.annotation.Message;
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import java.io.Serializable;
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/**
 * 消息类型分离器
 *
*
 * @author biws
 * @date 2020/11/20
 **/
@Message
public class Model implements Serializable {
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    private static final long serialVersionUID = 1L;
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    //类型
    private int type;
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    //内容
    private String body;
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    public int getType() {
        return type;
    }
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    public void setType(int type) {
        this.type = type;
    }
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    public String getBody() {
        return body;
    }
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    public void setBody(String body) {
        this.body = body;
    }
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    @Override
    public String toString() {
        return "Model{" +
                "type=" + type +
                ", body='" + body + '\'' +
                '}';
    }
}
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四、编码器
package com.gzky.study.netty;
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import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import org.msgpack.MessagePack;
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/**
 * 编码器
 *
*
 * @author biws
 * @date 2020/11/20
 **/
public class MsgPckEncode extends MessageToByteEncoder<Object> {
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    @Override
    protected void encode(ChannelHandlerContext ctx, Object msg, ByteBuf buf)
            throws Exception {
        // TODO Auto-generated method stub
        MessagePack pack = new MessagePack();
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        byte[] write = pack.write(msg);
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        buf.writeBytes(write);
    }
}
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五、解码器
package com.gzky.study.netty;
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import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageDecoder;
import org.msgpack.MessagePack;
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import java.util.List;
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/**
 * 解码器
 *
*
 * @author biws
 * @date 2020/11/20
 **/
public class MsgPckDecode extends MessageToMessageDecoder<ByteBuf> {
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    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf msg,
                          List<Object> out) throws Exception {
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        final  byte[] array;
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        final int length = msg.readableBytes();
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        array = new byte[length];
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        msg.getBytes(msg.readerIndex(), array, 0, length);
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        MessagePack pack = new MessagePack();
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        out.add(pack.read(array, Model.class));
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    }
}
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六、公用控制器
package com.gzky.study.netty;
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import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.timeout.IdleStateEvent;
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/**
 * 公用控制器
 *
 * @author biws
 * @date 2020/11/20
 **/
public abstract class Middleware extends ChannelInboundHandlerAdapter {
    protected String name;
    //记录次数
    private int heartbeatCount = 0;
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    //获取server and client 传入的值
    public Middleware(String name) {
        this.name = name;
    }
    /**
     *继承ChannelInboundHandlerAdapter实现了channelRead就会监听到通道里面的消息
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        Model m = (Model) msg;
        int type = m.getType();
        switch (type) {
            case 1:
                sendPongMsg(ctx);
                break;
            case 2:
                System.out.println(name + " get  pong  msg  from" + ctx.channel().remoteAddress());
                break;
            case 3:
                handlerData(ctx,msg);
                break;
            default:
                break;
        }
    }
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    protected abstract void handlerData(ChannelHandlerContext ctx,Object msg);
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    protected void sendPingMsg(ChannelHandlerContext ctx){
        Model model = new Model();
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        model.setType(TypeData.PING);
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        ctx.channel().writeAndFlush(model);
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        heartbeatCount++;
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        System.out.println(name + " send ping msg to " + ctx.channel().remoteAddress() + "count :" + heartbeatCount);
    }
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    private void sendPongMsg(ChannelHandlerContext ctx) {
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        Model model = new Model();
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        model.setType(TypeData.PONG);
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        ctx.channel().writeAndFlush(model);
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        heartbeatCount++;
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        System.out.println(name +" send pong msg to "+ctx.channel().remoteAddress() +" , count :" + heartbeatCount);
    }
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    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt)
            throws Exception {
        IdleStateEvent stateEvent = (IdleStateEvent) evt;
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        switch (stateEvent.state()) {
            case READER_IDLE:
                handlerReaderIdle(ctx);
                break;
            case WRITER_IDLE:
                handlerWriterIdle(ctx);
                break;
            case ALL_IDLE:
                handlerAllIdle(ctx);
                break;
            default:
                break;
        }
    }
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    protected void handlerAllIdle(ChannelHandlerContext ctx) {
        System.err.println("---ALL_IDLE---");
    }
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    protected void handlerWriterIdle(ChannelHandlerContext ctx) {
        System.err.println("---WRITER_IDLE---");
    }
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    protected void handlerReaderIdle(ChannelHandlerContext ctx) {
        System.err.println("---READER_IDLE---");
    }
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    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        // TODO Auto-generated method stub
        System.err.println(" ---"+ctx.channel().remoteAddress() +"----- is  action" );
    }
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    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        // TODO Auto-generated method stub
        System.err.println(" ---"+ctx.channel().remoteAddress() +"----- is  inAction");
    }
}
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七、客户端
package com.gzky.study.netty;
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import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.timeout.IdleStateHandler;
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import java.util.Scanner;
import java.util.concurrent.TimeUnit;
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/**
 * Client客户端
*
 * @author biws
 * @date 2020/11/20
 **/
public class Client {
    private NioEventLoopGroup worker = new NioEventLoopGroup();
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    private Channel channel;
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    private Bootstrap bootstrap;
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    boolean flag = true;
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    public static void main(String[] args) {
        Client client = new Client();
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        client.start();
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        client.sendData();
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		//通信结束，关闭客户端
        client.close();
    }
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    private void close() {
        channel.close();
        worker.shutdownGracefully();
    }
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    private void start() {
        bootstrap = new Bootstrap();
        bootstrap.group(worker)
                .channel(NioSocketChannel.class)
                .option(ChannelOption.TCP_NODELAY, true)
                .handler(new ChannelInitializer<Channel>() {
                    @Override
                    protected void initChannel(Channel ch) throws Exception {
                        // TODO Auto-generated method stub
                        ChannelPipeline pipeline = ch.pipeline();
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                        pipeline.addLast(new IdleStateHandler(3, 3, 5));
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                        pipeline.addLast(new MsgPckDecode());
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                        pipeline.addLast(new MsgPckEncode());
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                        pipeline.addLast(new Client3Handler(Client.this));
                    }
                });
        doConnect();
    }
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    /**
     * 连接服务端 and 重连
     */
    protected void doConnect() {
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        if (channel != null && channel.isActive()) {
            return;
        }
        ChannelFuture connect = bootstrap.connect("127.0.0.1", 8089);
        //实现监听通道连接的方法
        connect.addListener(new ChannelFutureListener() {
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            @Override
            public void operationComplete(ChannelFuture channelFuture) throws Exception {
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                if (channelFuture.isSuccess()) {
                    channel = channelFuture.channel();
                    System.out.println("连接成功");
                } else {
                    if (flag) {
                        System.out.println("每隔2s重连....");
                        channelFuture.channel().eventLoop().schedule(new Runnable() {
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                            @Override
                            public void run() {
                                // TODO Auto-generated method stub
                                doConnect();
                            }
                        }, 2, TimeUnit.SECONDS);
                    }
                }
            }
        });
    }
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    /**
     * 向服务端发送消息
     */
    private void sendData() {
    	//创建连接成功之前停在这里等待
        while (channel == null || !channel.isActive()) {
            System.out.println("等待连接···");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("连接成功等待输入：");
        flag = true;
        Scanner sc = new Scanner(System.in);
        while (flag) {
            String nextLine = sc.nextLine();
            if ("end".equalsIgnoreCase(nextLine)) {
                flag = false;
            }
            Model model = new Model();
            model.setType(TypeData.CUSTOMER);
            model.setBody(nextLine);
            channel.writeAndFlush(model);
        }
    }
}
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八、客户端控制器
package com.gzky.study.netty;
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import io.netty.channel.ChannelHandlerContext;
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/**
 * 客户端控制器
*
 * @author biws
 * @date 2020/11/20
 **/
public class Client3Handler extends Middleware {
    private Client client;
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    public Client3Handler(Client client) {
        super("client");
        this.client = client;
    }
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    @Override
    protected void handlerData(ChannelHandlerContext ctx, Object msg) {
        // TODO Auto-generated method stub
        Model model = (Model) msg;
        System.out.println("client  收到数据： " + model.toString());
    }
    @Override
    protected void handlerAllIdle(ChannelHandlerContext ctx) {
        // TODO Auto-generated method stub
        super.handlerAllIdle(ctx);
        sendPingMsg(ctx);
    }
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        // TODO Auto-generated method stub
        super.channelInactive(ctx);
        client.doConnect();
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        System.out.println(name + "exception :"+ cause.toString());
    }
}
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九、服务端
package com.gzky.study.netty;
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import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.timeout.IdleStateHandler;
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/**
 * 服务端
*
 * @author biws
 * @date 2020/11/20
 **/
public class Server {
    public static void main(String[] args) {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
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        EventLoopGroup workerGroup = new NioEventLoopGroup(4);
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
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            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .localAddress(8089)
                    .childHandler(new ChannelInitializer<Channel>() {
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                        @Override
                        protected void initChannel(Channel ch) throws Exception {
                            // TODO Auto-generated method stub
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new IdleStateHandler(10,3,10));
                            pipeline.addLast(new MsgPckDecode());
                            pipeline.addLast(new MsgPckEncode());
                            pipeline.addLast(new Server3Handler());
                        }
                    });
            System.out.println("start server 8089 --");
            ChannelFuture sync = serverBootstrap.bind().sync();
            sync.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            //优雅的关闭资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
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}
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十、服务端控制器
package com.gzky.study.netty;
﻿
import io.netty.channel.ChannelHandlerContext;
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/**
 * 服务端控制器
 *
 * @author biws
 * @date 2020/11/20
 **/
public class Server3Handler extends Middleware {
    public Server3Handler() {
        super("server");
        // TODO Auto-generated constructor stub
    }
    @Override
    protected void handlerData(ChannelHandlerContext ctx, Object msg) {
        // TODO Auto-generated method stub
        Model model  = (Model) msg;
        System.out.println("server 接收数据 ： " +  model.toString());
        model.setType(TypeData.CUSTOMER);
        model.setBody("client你好，server已接收到数据："+model.getBody());
        ctx.channel().writeAndFlush(model);
        System.out.println("server 发送数据： " + model.toString());
    }
    @Override
    protected void handlerReaderIdle(ChannelHandlerContext ctx) {
        // TODO Auto-generated method stub
        super.handlerReaderIdle(ctx);
        System.err.println(" ---- client "+ ctx.channel().remoteAddress().toString() + " reader timeOut, --- close it");
        ctx.close();
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        System.err.println( name +"  exception" + cause.toString());
    }
}
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十一、测试1、启动服务端
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2、启动客户端
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3、客户端发消息﻿
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服务端控制台就可以收到hello，并且回信。
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好了，到这里，netty - springboot - 长连接 - 心跳 - 自动重连 - 通信就完成了，不知道你实现了没有，建议你可以先收藏，等有时间了自己实现一下，尤其是刚接触的，觉得写得还不错的，可以转发一下，让更多人看见，谢谢
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新的技术学习必定是充满BUG的，但是，解决了就是一片光明，这样一点点的改BUG中，剩下的就是你成长的路径
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希望可以对大家有帮助，喜欢的小伙伴可以关注公众号：小迁不秃头，每天不定时更新，干货满满！