netty解决粘包问题，利用ReplayingDecoder

Question

问题描述

利用netty的ReplayingDecoder解决tcp的粘包和拆包问题

问题出现的环境背景及自己尝试过哪些方法

当客户端发送10条数据给服务器端时，服务器端只接收到了一条总的消息

相关代码

// 请把代码文本粘贴到下方（请勿用图片代替代码）

PersonProtocol.java

public class PersonProtocol {
    private int length;

    private byte[] content;

    public int getLength() {
        return length;
    }

    public void setLength(int length) {
        this.length = length;
    }

    public byte[] getContent() {
        return content;
    }

    public void setContent(byte[] content) {
        this.content = content;
    }
}

PersonDecoder.java

public class PersonDecoder extends ReplayingDecoder<Void> {

    @Override
    protected void decode(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf, List<Object> list) throws Exception {
        int length = byteBuf.readInt();
        byte[] content = new byte[length];
        byteBuf.readBytes(content);

        PersonProtocol personProtocol = new PersonProtocol();
        personProtocol.setLength(length);
        personProtocol.setContent(content);
        list.add(personProtocol);
    }
}

PersonEncoder.java

public class PersonEncoder extends MessageToByteEncoder<PersonProtocol> {

    @Override
    protected void encode(ChannelHandlerContext ctx, PersonProtocol msg, ByteBuf out) throws Exception {
        int length = msg.getLength();
        byte[] content = msg.getContent();

        out.writeInt(length);
        out.writeBytes(content);
    }
}

Server.java

public class Server {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try{
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class).childHandler(new ServerInitlization());
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

ServerInitlization.java

public class ServerInitlization extends ChannelInitializer<Channel> {
    @Override
    protected void initChannel(Channel channel) throws Exception {
        ChannelPipeline pipeline = channel.pipeline();

        pipeline.addLast(new PersonDecoder());
        pipeline.addLast(new PersonEncoder());
        pipeline.addLast(new ServerHandler());
    }
}

ServerHandler.java

public class ServerHandler extends SimpleChannelInboundHandler<PersonProtocol> {
    private int count = 0;
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, PersonProtocol msg) throws Exception {
        String content = new String(msg.getContent(), Charset.forName("utf-8"));
        System.out.println("Server - 接收到的消息为：" + content);
        System.out.println("Server - 接收到的消息体长度为：" + content.length());
        System.out.println("Server - 接收到的消息数量为：" + (++count));

        String result = new String("Server接收到的消息为："+content);
        PersonProtocol personProtocol = new PersonProtocol();
        personProtocol.setLength(result.length());
        personProtocol.setContent(result.getBytes(Charset.forName("utf-8")));
        ctx.writeAndFlush(personProtocol);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
    }
}

Client.java

public class Client {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup worker = new NioEventLoopGroup();

        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(worker).channel(NioSocketChannel.class).handler(new ClientInitialization());
            ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            worker.shutdownGracefully();
        }
    }
}

ClientInitialization.java

public class ClientInitialization extends ChannelInitializer<Channel> {
    @Override
    protected void initChannel(Channel ch) throws Exception {
        ChannelPipeline channelPipeline = ch.pipeline();

        channelPipeline.addLast(new PersonDecoder());
        channelPipeline.addLast(new PersonEncoder());
        channelPipeline.addLast(new ClientHandler());
    }
}

ClientHandler.java

public class ClientHandler extends SimpleChannelInboundHandler<PersonProtocol> {
    private int count = 0;
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, PersonProtocol msg) throws Exception {
        System.out.println("Client - 接收消息：" + msg.getContent());
        System.out.println("Client - 接收消息长度：" + msg.getLength());
        System.out.println(++count);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        for(int i = 0 ; i < 10 ; i++){
            String body = "来自客户端" + UUID.randomUUID().toString() + ":" + "发送的消息：" + i;
            PersonProtocol personProtocol = new PersonProtocol();
            personProtocol.setLength(body.length());
            personProtocol.setContent(body.getBytes());
            ctx.writeAndFlush(personProtocol);
            System.out.println("123");
        }
    }
}

你期待的结果是什么？实际看到的错误信息又是什么？

结果：
服务器端：
Server - 接收到的消息为：来自客户端caa4be43-1957-4d72-8866-518e6dba56
Server - 接收到的消息体长度为：39
Server - 接收到的消息数量为：1
客户端：
123
123
123
123
123
123
123
123
123
123
Client - 接收消息：[B@7cb85a04
Client - 接收消息长度：53
1

期望的结果是服务器端能够收到来自客户端发来的10条消息。