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; @Autowired ProjectInitializer nettyInitializer; @PostConstruct public 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channel bootstrap.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 */ @PreDestroy public void destroy() throws InterruptedException { if (bossGroup != null) { bossGroup.shutdownGracefully().sync(); } if (workGroup != null) { workGroup.shutdownGracefully().sync(); } } }
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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); } }
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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; @Autowired WebSocketHandler webSocketHandler; @Override protected 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 */ @Override public 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 */ @Override protected 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channel JSONObject 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ID AttributeKey<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")); } @Override public 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); } @Override public 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 { @Override public 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)); } @Override public 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。
