netty中的WebSocket长连接开发

一、netty中的WebSocket长连接开发

在Netty中开发WebSocket长连接需要完成以下步骤：

创建WebSocket服务器
配置WebSocket服务器的ChannelHandler
实现业务处理逻辑

下面是相关的示例代码：

public class WebSocketServer {
    private static final String HOST = "127.0.0.1";
    private static final int PORT = 8888;

    public void start() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap()
                    .group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            // 配置WebSocket协议参数
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new HttpServerCodec());
                            pipeline.addLast(new HttpObjectAggregator(65536));
                            pipeline.addLast(new ChunkedWriteHandler());
                            pipeline.addLast(new WebSocketServerProtocolHandler("/ws"));
                            
                            // 自定义的WebSocket消息处理器
                            pipeline.addLast(new MyWebSocketHandler());
                        }
                    });

            ChannelFuture future = bootstrap.bind(HOST, PORT).sync();
            System.out.println("WebSocket server started at port " + PORT);
            future.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        new WebSocketServer().start();
    }
}

在上述代码中，我们采用了Netty的ServerBootstrap来创建WebSocket服务器。在通道的pipeline中添加了一些WebSocket协议相关的处理器：

HttpServerCodec：将HTTP请求和响应消息编解码为HTTP消息
HttpObjectAggregator：聚合HTTP消息分段
ChunkedWriteHandler：支持异步写大的码流（例如大文件传输），但不占用过多的内存，防止发生Java内存溢出
WebSocketServerProtocolHandler：实现WebSocket协议的握手和控制帧处理

同时，我们还自定义了一个MyWebSocketHandler类来实现业务逻辑，该类需要继承ChannelInboundHandlerAdapter或其子类，并重写channelRead方法。

public class MyWebSocketHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof TextWebSocketFrame) {
            String text = ((TextWebSocketFrame) msg).text();
            System.out.println("Received message: " + text);
            
            // 业务逻辑处理代码...
            
            // 发送消息给客户端
            ctx.channel().writeAndFlush(new TextWebSocketFrame("Hello, client!"));
        } else {
            super.channelRead(ctx, msg);
        }
    }

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