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来源 | blog.csdn.net/weixin_44912855

学过 Netty 的都知道，Netty 对 NIO 进行了很好的封装，简单的 API，庞大的开源社区。深受广大程序员喜爱。基于此本文分享一下基础的 netty 使用。实战制作一个 Netty + websocket 的消息推送小栗子。

netty服务器

@Component
public class NettyServer {static final Logger log = LoggerFactory.getLogger(NettyServer.class);/*** 端口号*/@Value("${webSocket.netty.port:8888}")int port;EventLoopGroup bossGroup;EventLoopGroup workGroup;@AutowiredProjectInitializer nettyInitializer;@PostConstructpublic void start() throws InterruptedException {new Thread(() -> {bossGroup = new NioEventLoopGroup();workGroup = new NioEventLoopGroup();ServerBootstrap bootstrap = new ServerBootstrap();// bossGroup辅助客户端的tcp连接请求, workGroup负责与客户端之前的读写操作bootstrap.group(bossGroup, workGroup);// 设置NIO类型的channelbootstrap.channel(NioServerSocketChannel.class);// 设置监听端口bootstrap.localAddress(new InetSocketAddress(port));// 设置管道bootstrap.childHandler(nettyInitializer);// 配置完成，开始绑定server，通过调用sync同步方法阻塞直到绑定成功ChannelFuture channelFuture = null;try {channelFuture = bootstrap.bind().sync();log.info("Server started and listen on:{}", channelFuture.channel().localAddress());// 对关闭通道进行监听channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {e.printStackTrace();}}).start();}/*** 释放资源*/@PreDestroypublic void destroy() throws InterruptedException {if (bossGroup != null) {bossGroup.shutdownGracefully().sync();}if (workGroup != null) {workGroup.shutdownGracefully().sync();}}
}

Netty配置

管理全局Channel以及用户对应的channel（推送消息）

public class NettyConfig {/*** 定义全局单利channel组 管理所有channel*/private static volatile ChannelGroup channelGroup = null;/*** 存放请求ID与channel的对应关系*/private static volatile ConcurrentHashMap<String, Channel> channelMap = null;/*** 定义两把锁*/private static final Object lock1 = new Object();private static final Object lock2 = new Object();public static ChannelGroup getChannelGroup() {if (null == channelGroup) {synchronized (lock1) {if (null == channelGroup) {channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);}}}return channelGroup;}public static ConcurrentHashMap<String, Channel> getChannelMap() {if (null == channelMap) {synchronized (lock2) {if (null == channelMap) {channelMap = new ConcurrentHashMap<>();}}}return channelMap;}public static Channel getChannel(String userId) {if (null == channelMap) {return getChannelMap().get(userId);}return channelMap.get(userId);}
}

管道配置

@Component
public class ProjectInitializer extends ChannelInitializer<SocketChannel> {/*** webSocket协议名*/static final String WEBSOCKET_PROTOCOL = "WebSocket";/*** webSocket路径*/@Value("${webSocket.netty.path:/webSocket}")String webSocketPath;@AutowiredWebSocketHandler webSocketHandler;@Overrideprotected void initChannel(SocketChannel socketChannel) throws Exception {// 设置管道ChannelPipeline pipeline = socketChannel.pipeline();// 流水线管理通道中的处理程序（Handler），用来处理业务// webSocket协议本身是基于http协议的，所以这边也要使用http编解码器pipeline.addLast(new HttpServerCodec());pipeline.addLast(new ObjectEncoder());// 以块的方式来写的处理器pipeline.addLast(new ChunkedWriteHandler());pipeline.addLast(new HttpObjectAggregator(8192));pipeline.addLast(new WebSocketServerProtocolHandler(webSocketPath, WEBSOCKET_PROTOCOL, true, 65536 * 10));// 自定义的handler，处理业务逻辑pipeline.addLast(webSocketHandler);}
}

自定义handler

@Component
@ChannelHandler.Sharable
public class WebSocketHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {private static final Logger log = LoggerFactory.getLogger(NettyServer.class);/*** 一旦连接，第一个被执行*/@Overridepublic void handlerAdded(ChannelHandlerContext ctx) throws Exception {log.info("有新的客户端链接：[{}]", ctx.channel().id().asLongText());// 添加到channelGroup 通道组NettyConfig.getChannelGroup().add(ctx.channel());}/*** 读取数据*/@Overrideprotected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {log.info("服务器收到消息：{}", msg.text());// 获取用户ID,关联channelJSONObject jsonObject = JSONUtil.parseObj(msg.text());String uid = jsonObject.getStr("uid");NettyConfig.getChannelMap().put(uid, ctx.channel());// 将用户ID作为自定义属性加入到channel中，方便随时channel中获取用户IDAttributeKey<String> key = AttributeKey.valueOf("userId");ctx.channel().attr(key).setIfAbsent(uid);// 回复消息ctx.channel().writeAndFlush(new TextWebSocketFrame("服务器收到消息啦"));}@Overridepublic void handlerRemoved(ChannelHandlerContext ctx) throws Exception {log.info("用户下线了:{}", ctx.channel().id().asLongText());// 删除通道NettyConfig.getChannelGroup().remove(ctx.channel());removeUserId(ctx);}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {log.info("异常：{}", cause.getMessage());// 删除通道NettyConfig.getChannelGroup().remove(ctx.channel());removeUserId(ctx);ctx.close();}/*** 删除用户与channel的对应关系*/private void removeUserId(ChannelHandlerContext ctx) {AttributeKey<String> key = AttributeKey.valueOf("userId");String userId = ctx.channel().attr(key).get();NettyConfig.getChannelMap().remove(userId);}
}

推送消息接口及实现类

public interface PushMsgService {/*** 推送给指定用户*/void pushMsgToOne(String userId, String msg);/*** 推送给所有用户*/void pushMsgToAll(String msg);}

@Service
public class PushMsgServiceImpl implements PushMsgService {@Overridepublic void pushMsgToOne(String userId, String msg) {Channel channel = NettyConfig.getChannel(userId);if (Objects.isNull(channel)) {throw new RuntimeException("未连接socket服务器");}channel.writeAndFlush(new TextWebSocketFrame(msg));}@Overridepublic void pushMsgToAll(String msg) {NettyConfig.getChannelGroup().writeAndFlush(new TextWebSocketFrame(msg));}
}

测试

链接服务器

发送消息

调用接口，往前端推送消息！

OK！

一个简单的 netty 小栗子就完成了。

源码地址：https://gitee.com/dugt/springboot-netty-demo

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开发者：KaiFaX

面向全栈工程师的开发者
专注于前端、Java/Python/Go/PHP的技术社区