Netty是一个非常优秀的Socket框架。如果需要在SpringBoot开发的app中，提供Socket服务，那么Netty是不错的选择。

Netty与SpringBoot的整合，我想无非就是要整合几个地方

• 让netty跟springboot生命周期保持一致，同生共死
• 让netty能用上ioc中的Bean
• 让netty能读取到全局的配置

整合Netty，提供WebSocket服务

这里演示一个案例，在SpringBoot中使用Netty提供一个Websocket服务。

servlet容器本身提供了websocket的实现，但这里用netty的实现 :sparkling_heart:

添加依赖

<dependency> <groupId>io.netty</groupId> <artifactId>netty-all</artifactId></dependency>

是的，不用声明版本号。因为spring-boot-dependencies中已经声明了最新的netty依赖。

通过yaml配置基本的属性

server: port: 80logging: level: root: DEBUGmanagement: endpoints: web: exposure: include: "*" endpoint: shutdown: enabled: truenetty: websocket: # Websocket服务端口 port: 1024 # 绑定的网卡 ip: 0.0.0.0 # 消息帧最大体积 max-frame-size: 10240 # URI路径 path: /channel

App使用了，actuator ，并且开启暴露了 shutdown 端点，可以让SpringBoot App优雅的停机。 在这里通过 netty.websocket.* 配置 websocket服务相关的配置。

通过 ApplicationRunner 启动Websocket服务

import java.net.InetSocketAddress;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.BeansException;import org.springframework.beans.factory.annotation.Value;import org.springframework.boot.ApplicationArguments;import org.springframework.boot.ApplicationRunner;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;import org.springframework.context.ApplicationListener;import org.springframework.context.event.ContextClosedEvent;import org.springframework.stereotype.Component;import io.netty.bootstrap.ServerBootstrap;import io.netty.channel.Channel;import io.netty.channel.ChannelFutureListener;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelPipeline;import io.netty.channel.EventLoopGroup;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioServerSocketChannel;import io.netty.handler.codec.http.DefaultFullHttpResponse;import io.netty.handler.codec.http.FullHttpRequest;import io.netty.handler.codec.http.HttpObjectAggregator;import io.netty.handler.codec.http.HttpResponseStatus;import io.netty.handler.codec.http.HttpServerCodec;import io.netty.handler.codec.http.HttpVersion;import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;import io.netty.handler.codec.http.websocketx.extensions.compression.WebSocketServerCompressionHandler;import io.netty.handler.stream.ChunkedWriteHandler;import io.springboot.netty.websocket.handler.WebsocketMessageHandler;/** * 初始化Netty服务 * @author Administrator */@Componentpublic class NettyBootsrapRunner implements ApplicationRunner, ApplicationListener<ContextClosedEvent>, ApplicationContextAware { private static final Logger LOGGER = LoggerFactory.getLogger(NettyBootsrapRunner.class); @Value("${netty.websocket.port}") private int port; @Value("${netty.websocket.ip}") private String ip; @Value("${netty.websocket.path}") private String path; @Value("${netty.websocket.max-frame-size}") private long maxFrameSize; private ApplicationContext applicationContext; private Channel serverChannel; public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; } public void run(ApplicationArguments args) throws Exception { EventLoopGroup bossGroup = new NioEventLoopGroup(); EventLoopGroup workerGroup = new NioEventLoopGroup(); try { ServerBootstrap serverBootstrap = new ServerBootstrap(); serverBootstrap.group(bossGroup, workerGroup); serverBootstrap.channel(NioServerSocketChannel.class); serverBootstrap.localAddress(new InetSocketAddress(this.ip, this.port)); serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel socketChannel) throws Exception { ChannelPipeline pipeline = socketChannel.pipeline(); pipeline.addLast(new HttpServerCodec()); pipeline.addLast(new ChunkedWriteHandler()); pipeline.addLast(new HttpObjectAggregator(65536)); pipeline.addLast(new ChannelInboundHandlerAdapter() { @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { if(msg instanceof FullHttpRequest) { FullHttpRequest fullHttpRequest = (FullHttpRequest) msg; String uri = fullHttpRequest.uri(); if (!uri.equals(path)) { // 访问的路径不是 websocket的端点地址，响应404 ctx.channel().writeAndFlush(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.NOT_FOUND)) .addListener(ChannelFutureListener.CLOSE); return ; } } super.channelRead(ctx, msg); } }); pipeline.addLast(new WebSocketServerCompressionHandler()); pipeline.addLast(new WebSocketServerProtocolHandler(path, null, true, maxFrameSize)); /** * 从IOC中获取到Handler */ pipeline.addLast(applicationContext.getBean(WebsocketMessageHandler.class)); } }); Channel channel = serverBootstrap.bind().sync().channel(); this.serverChannel = channel; LOGGER.info("websocket 服务启动，ip={},port={}", this.ip, this.port); channel.closeFuture().sync(); } finally { bossGroup.shutdownGracefully(); workerGroup.shutdownGracefully(); } } public void onApplicationEvent(ContextClosedEvent event) { if (this.serverChannel != null) { this.serverChannel.close(); } LOGGER.info("websocket 服务停止"); }}

NettyBootsrapRunner 实现了 ApplicationRunner, ApplicationListener<ContextClosedEvent> , ApplicationContextAware 接口。

这样一来， NettyBootsrapRunner 可以在App的启动和关闭时执行Websocket服务的启动和关闭。而且通过 ApplicationContextAware 还能获取到 ApplicationContext

通过IOC管理 Netty 的Handler

import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.SimpleChannelInboundHandler;import io.netty.channel.ChannelFutureListener;import io.netty.channel.ChannelHandler.Sharable;import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;import io.netty.handler.codec.http.websocketx.WebSocketCloseStatus;import io.netty.handler.codec.http.websocketx.WebSocketFrame;import io.springboot.netty.service.DiscardService;/** * * @author Administrator * */@Sharable@Componentpublic class WebsocketMessageHandler extends SimpleChannelInboundHandler<WebSocketFrame> { private static final Logger LOGGER = LoggerFactory.getLogger(WebsocketMessageHandler.class); @Autowired DiscardService discardService; @Override protected void channelRead0(ChannelHandlerContext ctx, WebSocketFrame msg) throws Exception { if (msg instanceof TextWebSocketFrame) { TextWebSocketFrame textWebSocketFrame = (TextWebSocketFrame) msg; // 业务层处理数据 this.discardService.discard(textWebSocketFrame.text()); // 响应客户端 ctx.channel().writeAndFlush(new TextWebSocketFrame("我收到了你的消息：" + System.currentTimeMillis())); } else { // 不接受文本以外的数据帧类型 ctx.channel().writeAndFlush(WebSocketCloseStatus.INVALID_MESSAGE_TYPE).addListener(ChannelFutureListener.CLOSE); } } @Override public void channelInactive(ChannelHandlerContext ctx) throws Exception { super.channelInactive(ctx); LOGGER.info("链接断开：{}", ctx.channel().remoteAddress()); } @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { super.channelActive(ctx); LOGGER.info("链接创建：{}", ctx.channel().remoteAddress()); }}

handler已经是一个IOC管理的Bean，可以自由的使用依赖注入等Spring带来的快捷功能。由于是单例存在，所有的链接都使用同一个hander，所以尽量不要保存任何实例变量。

这个Handler处理完毕客户端的消息后，给客户端会响应一条： "我收到了你的消息：" + System.currentTimeMillis() 的消息

为了演示在Handler中使用业务层，这里假装注入了一个 DiscardService 服务。它的逻辑很简单，就是丢弃消息

public void discard (String message) { LOGGER.info("丢弃消息:{}", message);}

演示

启动客户端

<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Websocket</title> </head> <body> </body> <script type="text/javascript"> ;(function(){ const websocket = new WebSocket('ws://localhost:1024/channel'); websocket.onmessage = e => { console.log('收到消息:', e.data); } websocket.onclose = e => { let {code, reason} = e; console.log(`链接断开:code=$[code], reason=${reason}`); } websocket.onopen = () => { console.log(`链接建立...`); websocket.send('Hello'); } websocket.onerror = e => { console.log('链接异常:', e); } })(); </script></html>

链接创建后就给服务端发送一条消息： Hello

关闭服务端

使用 PostMan 请求服务器的停机端点

日志

客户端日志

服务端日志

2020-06-22 17:08:22.728 INFO 9392 --- [ main] io.undertow : starting server: Undertow - 2.1.3.Final
2020-06-22 17:08:22.740 INFO 9392 --- [ main] org.xnio : XNIO version 3.8.0.Final
2020-06-22 17:08:22.752 INFO 9392 --- [ main] org.xnio.nio : XNIO NIO Implementation Version 3.8.0.Final
2020-06-22 17:08:22.839 INFO 9392 --- [ main] org.jboss.threads : JBoss Threads version 3.1.0.Final
2020-06-22 17:08:22.913 INFO 9392 --- [ main] o.s.b.w.e.undertow.UndertowWebServer : Undertow started on port(s) 80 (http)
2020-06-22 17:08:22.931 INFO 9392 --- [ main] io.springboot.netty.NettyApplication : Started NettyApplication in 4.536 seconds (JVM running for 5.175)
2020-06-22 17:08:23.653 INFO 9392 --- [ main] i.s.n.w.runner.NettyBootsrapRunner : websocket 服务启动，ip=0.0.0.0,port=1024
2020-06-22 17:08:28.484 INFO 9392 --- [ XNIO-1 task-1] io.undertow.servlet : Initializing Spring DispatcherServlet 'dispatcherServlet'
2020-06-22 17:08:28.484 INFO 9392 --- [ XNIO-1 task-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2020-06-22 17:08:28.492 INFO 9392 --- [ XNIO-1 task-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 8 ms
2020-06-22 17:08:28.724 INFO 9392 --- [ntLoopGroup-3-1] i.s.n.w.handler.WebsocketMessageHandler : 链接创建：/0:0:0:0:0:0:0:1:12093
2020-06-22 17:08:28.790 INFO 9392 --- [ntLoopGroup-3-1] i.s.netty.service.DiscardService : 丢弃消息:Hello
2020-06-22 17:08:33.688 INFO 9392 --- [ Thread-232] i.s.n.w.runner.NettyBootsrapRunner : websocket 服务停止
2020-06-22 17:08:33.691 INFO 9392 --- [ntLoopGroup-3-1] i.s.n.w.handler.WebsocketMessageHandler : 链接断开：/0:0:0:0:0:0:0:1:12093
2020-06-22 17:08:33.699 INFO 9392 --- [ Thread-232] io.undertow : stopping server: Undertow - 2.1.3.Final
2020-06-22 17:08:33.704 INFO 9392 --- [ Thread-232] io.undertow.servlet : Destroying Spring FrameworkServlet 'dispatcherServlet'
2020-06-22 17:08:33.708 INFO 9392 --- [ Thread-232] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor'

Netty会在SpringBoot App启动后启动，App停止后关闭，可以正常的对外提供服务 并且Handler交给IOC管理可以注入Service，完成业务处理。

总结

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