java netty实现客户端和服务端长连接的完整代码

在Java中，Netty是一个高性能的网络应用框架，非常适合实现客户端和服务端的长连接。以下是一个简单的Netty示例，展示了如何创建一个TCP服务器和客户端进行全双工通信：

**服务端（Server.java）：**

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;

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

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new LineBasedFrameDecoder(1024));
                            ch.pipeline().addLast(new StringDecoder());
                            ch.pipeline().addLast(new SimpleServerHandler());
                        }
                    });

            ChannelFuture f = b.bind(8080).sync();
            System.out.println("Server started and listening on port " + f.channel().localAddress());

            // Keep the server running until interrupted.
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }
}

// ... (定义SimpleServerHandler类处理客户端消息)

**客户端（Client.java）：**

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;

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

        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new LineBasedFrameEncoder(1024));
                            ch.pipeline().addLast(new StringDecoder());
                            ch.pipeline().addLast(new SimpleClientHandler());
                        }
                    });

            ChannelFuture f = b.connect("localhost", 8080).sync();
            SocketChannel channel = (SocketChannel) f.channel();
            channel.writeAndFlush("Hello Server!");

            // Read and process messages from the server.
            String response = "";
            byte[] data = new byte[1024];
            while ((response = channel.readBytes(data)) > 0) {
                System.out.println("Received: " + new String(data, 0, response));
            }

            // Gracefully close the connection when done.
            channel.close();
        } finally {
            group.shutdownGracefully();
        }
    }
}

// ... (定义SimpleClientHandler类发送请求并处理响应)

在这个例子中，`LineBasedFrameDecoder`用于拆分行，`StringDecoder`将字节流转换为字符串。`SimpleServerHandler`和`SimpleClientHandler`是自定义处理器，用于服务器和客户端的实际业务逻辑。