利用Java搭建个简单的Netty通信实例教程

<dependencies>
  <!-- Netty -->
  <dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.10.Final</version>
  </dependency>

  <dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.25</version>
  </dependency>

  <!-- Protostuff -->
  <dependency>
    <groupId>com.dyuproject.protostuff</groupId>
    <artifactId>protostuff-core</artifactId>
    <version>1.0.9</version>
  </dependency>

  <dependency>
    <groupId>com.dyuproject.protostuff</groupId>
    <artifactId>protostuff-runtime</artifactId>
    <version>1.0.9</version>
  </dependency>

  <!-- Objenesis -->
  <dependency>
    <groupId>org.objenesis</groupId>
    <artifactId>objenesis</artifactId>
    <version>2.1</version>
  </dependency>

  <!-- fastjson -->
  <dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.38</version>
  </dependency>
</dependencies>

public class Request {

  private String requestId;

  private Object parameter;

  public String getRequestId() {
    return requestId;
  }

  public void setRequestId(String requestId) {
    this.requestId = requestId;
  }

  public Object getParameter() {
    return parameter;
  }

  public void setParameter(Object parameter) {
    this.parameter = parameter;
  }
}

public class Response {

  private String requestId;

  private Object result;

  public String getRequestId() {
    return requestId;
  }

  public void setRequestId(String requestId) {
    this.requestId = requestId;
  }

  public Object getResult() {
    return result;
  }

  public void setResult(Object result) {
    this.result = result;
  }
}

public class RpcDecoder extends ByteToMessageDecoder {

  // 目标对象类型进行解码
  private Class<?> target;

  public RpcDecoder(Class target) {
    this.target = target;
  }

  @Override
  protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
    if (in.readableBytes() < 4) {  // 不够长度丢弃
      return;
    }
    in.markReaderIndex();  // 标记一下当前的readIndex的位置
    int dataLength = in.readInt(); // 读取传送过来的消息的长度。ByteBuf 的readInt()方法会让他的readIndex增加4

    if (in.readableBytes() < dataLength) { // 读到的消息体长度如果小于我们传送过来的消息长度，则resetReaderIndex. 这个配合markReaderIndex使用的。把readIndex重置到mark的地方
      in.resetReaderIndex();
      return;
    }
    byte[] data = new byte[dataLength];
    in.readBytes(data);

    Object obj = JSON.parseObject(data, target);  // 将byte数据转化为我们需要的对象
    out.add(obj);
  }
}

public class RpcEncoder extends MessageToByteEncoder {

  //目标对象类型进行编码
  private Class<?> target;

  public RpcEncoder(Class target) {
    this.target = target;
  }

  @Override
  protected void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out) throws Exception {
    if (target.isInstance(msg)) {
      byte[] data = JSON.toJSONBytes(msg);  // 使用fastJson将对象转换为byte
      out.writeInt(data.length); // 先将消息长度写入，也就是消息头
      out.writeBytes(data);  // 消息体中包含我们要发送的数据
    }
  }

}

public class NettyServerHandler extends ChannelInboundHandlerAdapter {

  @Override
  public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    Request request = (Request) msg;

    System.out.println("Client Data:" + JSON.toJSONString(request));

    Response response = new Response();
    response.setRequestId(request.getRequestId());
    response.setResult("Hello Client !");

    // client接收到信息后主动关闭掉连接
    ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
  }

  @Override
  public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    ctx.flush();
  }

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

public class NettyServer {

  private static final Logger logger = LoggerFactory.getLogger(NettyServer.class);

  private String ip;
  private int port;

  public NettyServer(String ip, int port) {
    this.ip = ip;
    this.port = port;
  }

  public void server() throws Exception {

    EventLoopGroup bossGroup = new NioEventLoopGroup();
    EventLoopGroup workerGroup = new NioEventLoopGroup();

    try {

      final ServerBootstrap serverBootstrap = new ServerBootstrap();

      serverBootstrap.group(bossGroup, workerGroup)
          .channel(NioServerSocketChannel.class)
          .option(ChannelOption.SO_BACKLOG, 1024)
          .option(ChannelOption.SO_SNDBUF, 32 * 1024)
          .option(ChannelOption.SO_RCVBUF, 32 * 1024)
          .option(ChannelOption.SO_KEEPALIVE, true)
          .childHandler(new ChannelInitializer<SocketChannel>() {
            protected void initChannel(SocketChannel socketChannel) throws Exception {
              socketChannel.pipeline().addLast(new RpcDecoder(Request.class))
                  .addLast(new RpcEncoder(Response.class))
                  .addLast(new NettyServerHandler());
            }
          });

      serverBootstrap.childOption(ChannelOption.SO_KEEPALIVE, true); // 开启长连接

      ChannelFuture future = serverBootstrap.bind(ip, port).sync();

//      if (future.isSuccess()) {
//
//        new Register().register("/yanzhenyidai/com.yanzhenyidai.server", ip + ":" + port);
//      }

      future.channel().closeFuture().sync();
    } finally {
      bossGroup.shutdownGracefully();
      workerGroup.shutdownGracefully();
    }
  }

  public static void main(String[] args) throws Exception {
    new NettyServer("127.0.0.1", 20000).server();
  }
}

public class NettyClient extends SimpleChannelInboundHandler<Response> {

  private final String ip;
  private final int port;
  private Response response;

  public NettyClient(String ip, int port) {
    this.ip = ip;
    this.port = port;
  }

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

  @Override
  protected void channelRead0(ChannelHandlerContext channelHandlerContext, Response response) throws Exception {
    this.response = response;
  }

  public Response client(Request request) throws Exception {
    EventLoopGroup group = new NioEventLoopGroup();

    try {

      // 创建并初始化 Netty 客户端 Bootstrap 对象
      Bootstrap bootstrap = new Bootstrap();
      bootstrap.group(group);
      bootstrap.channel(NioSocketChannel.class);
      bootstrap.handler(new ChannelInitializer<SocketChannel>() {
        @Override
        public void initChannel(SocketChannel channel) throws Exception {
          ChannelPipeline pipeline = channel.pipeline();

          pipeline.addLast(new RpcDecoder(Response.class));
          pipeline.addLast(new RpcEncoder(Request.class));
          pipeline.addLast(NettyClient.this);
        }
      });
      bootstrap.option(ChannelOption.TCP_NODELAY, true);


//      String[] discover = new Discover().discover("/yanzhenyidai/com.yanzhenyidai.server").split(":");

      // 连接 RPC 服务器
      ChannelFuture future = bootstrap.connect(ip, port).sync();

      // 写入 RPC 请求数据并关闭连接
      Channel channel = future.channel();

      channel.writeAndFlush(request).sync();
      channel.closeFuture().sync();

      return response;
    } finally {
      group.shutdownGracefully();
    }
  }

  public static void main(String[] args) throws Exception {
    Request request = new Request();
    request.setRequestId(UUID.randomUUID().toString());
    request.setParameter("Hello Server !");
    System.out.println(JSON.toJSONString(new NettyClient("127.0.0.1", 30000).client(request)));
  }
}