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Spring中Netty的应用

news 2025/11/1 14:14:39

基于 Spring Boot 3.x + Netty 4.1.x 的 服务端、客户端、WebFlux、WebSocket 四合一实践
含 完整源码、生命周期、线程模型、自动配置 解析

背景

Tomcat/Jetty 是阻塞式 Servlet 容器，高并发场景下线程消耗大。
Netty 采用 NIO + 事件驱动，单线程可支撑 万级连接。
Spring Boot 3.x 官方支持 WebFlux 与 Reactor Netty，整合更丝滑。

整体架构

mermaid-diagram

场景一：内嵌 Netty 作为 Web 容器（WebFlux）

1. 引入依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

spring-boot-starter-webflux 默认使用 Reactor Netty（Netty 的响应式封装）。

2. 自定义配置（可选）

@Configuration
public class NettyWebFluxConfig implements WebServerFactoryCustomizer<NettyReactiveWebServerFactory> {@Overridepublic void customize(NettyReactiveWebServerFactory factory) {factory.addServerCustomizers(httpServer ->httpServer.port(9000).option(ChannelOption.SO_BACKLOG, 1024).childOption(ChannelOption.TCP_NODELAY, true));}
}

3. 路由示例

@SpringBootApplication
public class WebFluxApplication {public static void main(String[] args) {SpringApplication.run(WebfluxApplication.class, args);}@Beanpublic RouterFunction<ServerResponse> route() {return RouterFunctions.route(GET("/hello"), req -> ServerResponse.ok().bodyValue("Hello Netty"));}
}

访问 http://localhost:9000/hello 即可返回 Hello Netty。

场景二：自定义 TCP/UDP 服务器

1. Maven 依赖

<dependency><groupId>io.netty</groupId><artifactId>netty-all</artifactId><version>4.1.110.Final</version>
</dependency>

2. 启动器（跟随 Spring 生命周期）

@Component
public class TcpServer implements SmartLifecycle {private final EventLoopGroup boss = new NioEventLoopGroup(1);private final EventLoopGroup worker = new NioEventLoopGroup(0);private Channel channel;@Overridepublic void start() {try {ServerBootstrap bootstrap = new ServerBootstrap().group(boss, worker).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) {ChannelPipeline p = ch.pipeline();p.addLast(new StringDecoder());p.addLast(new StringEncoder());p.addLast(new SimpleChannelInboundHandler<String>() {@Autowiredprivate EchoService service; // Spring 注入@Overrideprotected void channelRead0(ChannelHandlerContext ctx, String msg) {ctx.writeAndFlush(service.echo(msg));}});}});channel = bootstrap.bind(8888).sync().channel();} catch (InterruptedException e) {Thread.currentThread().interrupt();}}@Overridepublic void stop() {if (channel != null) channel.close();boss.shutdownGracefully();worker.shutdownGracefully();}@Overridepublic boolean isRunning() {return channel != null && channel.isActive();}
}

3. 业务 Service

@Service
public class EchoService {public String echo(String msg) {return "Echo: " + msg;}
}

场景三：WebSocket 长连接

@Component
public class WebSocketServer implements SmartLifecycle {@Overridepublic void start() throws Exception {ServerBootstrap bootstrap = new ServerBootstrap().group(new NioEventLoopGroup(1), new NioEventLoopGroup()).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) {ch.pipeline().addLast(new HttpServerCodec()).addLast(new HttpObjectAggregator(65536)).addLast(new WebSocketServerProtocolHandler("/ws")).addLast(new SimpleChannelInboundHandler<TextWebSocketFrame>() {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame frame) {ctx.writeAndFlush(new TextWebSocketFrame("Received: " + frame.text()));}});}});bootstrap.bind(9999).sync();}
}

客户端连接 ws://localhost:9999/ws 即可实时通信。

Spring Boot 自动装配源码走读

1. 入口：`ReactorNettyAutoConfiguration`

@AutoConfiguration
@ConditionalOnClass(HttpServer.class)
@EnableConfigurationProperties(ServerProperties.class)
public class ReactorNettyAutoConfiguration {@Beanpublic NettyReactiveWebServerFactory nettyReactiveWebServerFactory() {return new NettyReactiveWebServerFactory();}
}

2. 工厂创建 `ServerBootstrap`

public class NettyReactiveWebServerFactory extends AbstractReactiveWebServerFactory {@Overridepublic WebServer getWebServer(HttpHandler httpHandler) {return new NettyWebServer(HttpServer.create().port(getPort()).handle(new ReactorHttpHandlerAdapter(httpHandler)));}
}

生命周期与线程模型

阶段	线程	说明
启动	主线程	Spring Boot `SmartLifecycle`
Accept	Boss EventLoop	单线程处理连接事件
I/O	Worker EventLoop	多线程处理读写
业务	Worker 或自定义线程池	耗时任务外移

最佳实践

建议	配置
线程数	Boss=1，Worker=CPU*2
ChannelOption	`SO_BACKLOG=1024`, `TCP_NODELAY=true`
ChannelHandler	使用 `@Sharable` 保证单例
内存	`ByteBuf.release()` 避免泄漏

常见问题 FAQ

问题	解决
端口冲突	`server.port` 与 `netty.port` 分离
Handler 非 Spring Bean	使用 `@Component` + `@Autowired`
优雅关闭	`EventLoopGroup.shutdownGracefully()`