Netty章节二十三：Netty自定义实现粘包与粘包

Netty自定义实现粘包与粘包

TCP粘包与拆包 问题的展现程序

默认不适应任何编解码器的情况下

Server

public class MyServer {
    public static void main(String[] args) throws Exception {

        HashMap<Object, Object> objectObjectHashMap = new HashMap<>();
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();

            serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new MyServerInitializer());
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}
//----------------------------------------------------------------------
public class MyServerInitializer extends ChannelInitializer<SocketChannel> {

    /**
        每连接一个客户端initChannel就会被调用一次
     */
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();

        pipeline.addLast(new MyServerHandler());
    }
}
//----------------------------------------------------------------------
public class MyServerHandler extends SimpleChannelInboundHandler<ByteBuf> {

    /**记录服务器端接收到了几次*/
    private int count;

    /**
     * @param ctx 上下文，可以获取远程的信息，地址、连接对象
     * @param msg 客户端发来的请求对象
     * @throws Exception
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
        byte[] buffer = new byte[msg.readableBytes()];
        msg.readBytes(buffer);

        String message = new String(buffer, Charset.forName("utf-8"));

        System.out.println("服务器端接收到的消息内容：" + message);
        System.out.println("服务器端接收到的消息数量：" + (++count));

        //向客户端返回数据
        ByteBuf responseByteBuf = Unpooled.copiedBuffer(UUID.randomUUID().toString(), Charset.forName("utf-8"));
        ctx.writeAndFlush(responseByteBuf);
    }


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

Client

public class MyClient {
    public static void main(String[] args) throws Exception {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
                    .handler(new MyClientInitializer());
            //与对应的url建立连接通道
            ChannelFuture channelFuture = bootstrap.connect("localhost",8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            eventLoopGroup.shutdownGracefully();
        }

    }
}
//----------------------------------------------------------------------
public class MyClientInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();

        pipeline.addLast(new MyClientHandler());
    }
}
//----------------------------------------------------------------------
public class MyClientHandler extends SimpleChannelInboundHandler<ByteBuf> {

    private int count;

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        for (int i = 0; i < 5; i++) {
            ByteBuf buffer = Unpooled.copiedBuffer("sent from client", Charset.forName("utf-8"));
            ctx.writeAndFlush(buffer);
        }
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
        byte[] buffer = new byte[msg.readableBytes()];
        msg.readBytes(buffer);

        String message = new String(buffer, Charset.forName("utf-8"));

        System.out.println("客户端接收到的消息内容：" + message);
        System.out.println("客户端接收到的消息数量：" + (++count));
    }

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

测试

Server输出

服务器端接收到的消息内容：sent from clientsent from clientsent from clientsent from clientsent from client
服务器端接收到的消息数量：1

Client输出

客户端接收到的消息内容：9226b8cf-0e10-41db-9e0e-684310854fc1
客户端接收到的消息数量：1

很明显是错误的，我们一共发送了5条消息但是服务器端却把它当成了一条消息进行接收了

解决问题自定义粘包与拆包

协议对象

/**
 * 协议对象
 */
public class PersonProtocol {

    /**value 消息体的长度，向后再读取length个字节为一个消息，content的长度*/
    private int length;

    /**消息体，length表示的长度就是它的内容长度*/
    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;
    }
}

消息解码器

/**
 * 消息解码器，用于定义接收一个消息的粘包的规则
 */
public class MyPersonDecoder extends ReplayingDecoder<Void> {

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        System.out.println("MyPersonDecoder decoder invoked !");

        //读取一个int(4个字节)，它表示消息体的长度
        int length = in.readInt();

        //用于消息体内容
        byte[] content = new byte[length];
        in.readBytes(content);

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

        out.add(personProtocol);
    }
}

消息编码器

public class MyPersonEncoder extends MessageToByteEncoder<PersonProtocol> {
    @Override
    protected void encode(ChannelHandlerContext ctx, PersonProtocol msg, ByteBuf out) throws Exception {
        System.out.println("MyPersonEncoder encode invoked !");

        out.writeInt(msg.getLength());
        out.writeBytes(msg.getContent());
    }
}

Server

public class MyServer {
    public static void main(String[] args) throws Exception {

        HashMap<Object, Object> objectObjectHashMap = new HashMap<>();
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();

            serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new MyServerInitializer());
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}
//----------------------------------------------------------------------
public class MyServerInitializer extends ChannelInitializer<SocketChannel> {

    /**
        每连接一个客户端initChannel就会被调用一次
     */
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();

        pipeline.addLast(new MyPersonDecoder());
        pipeline.addLast(new MyPersonEncoder());
        pipeline.addLast(new MyServerHandler());
    }
}
//----------------------------------------------------------------------
public class MyServerHandler extends SimpleChannelInboundHandler<PersonProtocol> {

    /**记录服务器端接收到了几次*/
    private int count;

    /**
     * @param ctx 上下文，可以获取远程的信息，地址、连接对象
     * @param msg 客户端发来的请求对象
     * @throws Exception
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, PersonProtocol msg) throws Exception {
        int length = msg.getLength();
        byte[] content = msg.getContent();

        System.out.println("服务端接收到的数据：");
        System.out.println("长度：" + length);
        System.out.println("内容：" + new String(content, Charset.forName("utf-8")));

        System.out.println("服务器端接收到的消息数量：" + (++count));

        //向客户端返回数据
        String responseMessage = UUID.randomUUID().toString();
        byte[] responseContent = responseMessage.getBytes(Charset.forName("utf-8"));
        int responseLength  = responseContent.length;

        PersonProtocol personProtocol = new PersonProtocol();
        personProtocol.setLength(responseLength);
        personProtocol.setContent(responseContent);

        ctx.writeAndFlush(personProtocol);
    }


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

Client

public class MyClient {
    public static void main(String[] args) throws Exception {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {

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

                            pipeline.addLast(new MyPersonDecoder());
                            pipeline.addLast(new MyPersonEncoder());
                            pipeline.addLast(new MyClientHandler());
                        }
                    });
            //与对应的url建立连接通道
            ChannelFuture channelFuture = bootstrap.connect("localhost",8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            eventLoopGroup.shutdownGracefully();
        }

    }
}
//----------------------------------------------------------------------
public class MyClientHandler extends SimpleChannelInboundHandler<PersonProtocol> {

    private int count;

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        for (int i = 0; i < 5; i++) {
            String messageToBeSent = "sent from client";
            byte[] content = messageToBeSent.getBytes(Charset.forName("utf-8"));
            int length = content.length;

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

            ctx.writeAndFlush(personProtocol);
        }
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, PersonProtocol msg) throws Exception {
        int length = msg.getLength();
        byte[] content = msg.getContent();

        System.out.println("客户端接收到的消息： ");

        System.out.println("长度：" + length);
        System.out.println("内容：" + new String(content,Charset.forName("utf-8")));

        System.out.println("客户端接收到的消息数量：" + (++count));
    }

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