<dependency>
   <groupId>io.netty</groupId>
   <artifactId>netty-all</artifactId>
   <version>4.1.25.Final</version>
  </dependency>

@Component
public class WebSocketServer {

 /**
  * 主線程池
  */
 private EventLoopGroup bossGroup;
 /**
  * 工作線程池
  */
 private EventLoopGroup workerGroup;
 /**
  * 服務器
  */
 private ServerBootstrap server;
 /**
  * 回調
  */
 private ChannelFuture future;

 public void start() {
  future = server.bind(9001);
  System.out.println("netty server - 啟動成功");
 }

 public WebSocketServer() {
  bossGroup = new NioEventLoopGroup();
  workerGroup = new NioEventLoopGroup();

  server = new ServerBootstrap();
  server.group(bossGroup, workerGroup)
    .channel(NioServerSocketChannel.class)
    .childHandler(new WebsocketInitializer());
 }
}

public class WebsocketInitializer extends ChannelInitializer<SocketChannel> {
 
 @Override
 protected void initChannel(SocketChannel ch) throws Exception {
  ChannelPipeline pipeline = ch.pipeline();
  // ------------------
  // 用于支持Http協議
  // ------------------
  // websocket基于http協議，需要有http的編解碼器
  pipeline.addLast(new HttpServerCodec());
  // 對寫大數據流的支持
  pipeline.addLast(new ChunkedWriteHandler());
  // 添加對HTTP請求和響應的聚合器:只要使用Netty進行Http編程都需要使用
  //設置單次請求的文件的大小
  pipeline.addLast(new HttpObjectAggregator(1024 * 64));
  //webSocket 服務器處理的協議，用于指定給客戶端連接訪問的路由 :/ws
  pipeline.addLast(new WebSocketServerProtocolHandler("/ws"));
  // 添加Netty空閑超時檢查的支持
  // 1. 讀空閑超時（超過一定的時間會發送對應的事件消息）
  // 2. 寫空閑超時
  // 3. 讀寫空閑超時
  pipeline.addLast(new IdleStateHandler(4, 8, 12));
  //添加心跳處理
  pipeline.addLast(new HearBeatHandler());
  // 添加自定義的handler
  pipeline.addLast(new ChatHandler());

 }
}

@Component
public class NettyListener implements ApplicationListener<ContextRefreshedEvent> {

 @Resource
 private WebSocketServer websocketServer;

 @Override
 public void onApplicationEvent(ContextRefreshedEvent event) {
  if(event.getApplicationContext().getParent() == null) {
   try {
    websocketServer.start();
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
 }
}

public class UserChannelMap {
 /**
  * 用戶保存用戶id與通道的Map對象
  */
// private static Map<String, Channel> userChannelMap;

 /* static {
  userChannelMap = new HashMap<String, Channel>();
 }*/

 /**
  * 定義一個channel組，管理所有的channel
  * GlobalEventExecutor.INSTANCE 是全局的事件執行器，是一個單例
  */
 private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

 /**
  * 存放用戶與Chanel的對應信息，用于給指定用戶發送消息
  */
 private static ConcurrentHashMap<String,Channel> userChannelMap = new ConcurrentHashMap<>();

 private UserChannelMap(){}
 /**
  * 添加用戶id與channel的關聯
  * @param userNum
  * @param channel
  */
 public static void put(String userNum, Channel channel) {
  userChannelMap.put(userNum, channel);
 }

 /**
  * 根據用戶id移除用戶id與channel的關聯
  * @param userNum
  */
 public static void remove(String userNum) {
  userChannelMap.remove(userNum);
 }

 /**
  * 根據通道id移除用戶與channel的關聯
  * @param channelId 通道的id
  */
 public static void removeByChannelId(String channelId) {
  if(!StringUtils.isNotBlank(channelId)) {
   return;
  }
  for (String s : userChannelMap.keySet()) {
   Channel channel = userChannelMap.get(s);
   if(channelId.equals(channel.id().asLongText())) {
    System.out.println("客戶端連接斷開,取消用戶" + s + "與通道" + channelId + "的關聯");
    userChannelMap.remove(s);
    UserService userService = SpringUtil.getBean(UserService.class);
    userService.logout(s);
    break;
   }
  }
 }

 /**
  * 打印所有的用戶與通道的關聯數據
  */
 public static void print() {
  for (String s : userChannelMap.keySet()) {
   System.out.println("用戶id:" + s + " 通道:" + userChannelMap.get(s).id());
  }
 }

 /**
  * 根據好友id獲取對應的通道
  * @param receiverNum 接收人編號
  * @return Netty通道
  */
 public static Channel get(String receiverNum) {
  return userChannelMap.get(receiverNum);
 }

 /**
  * 獲取channel組
  * @return
  */
 public static ChannelGroup getChannelGroup() {
  return channelGroup;
 }

 /**
  * 獲取用戶channel map
  * @return
  */
 public static ConcurrentHashMap<String,Channel> getUserChannelMap(){
  return userChannelMap;
 }
}

public class Message {
 /**
  * 消息類型
  */
 private Integer type;
 /**
  * 聊天消息
  */
 private String message;
 /**
  * 擴展消息字段
  */
 private Object ext;
 public Integer getType() {
  return type;
 }

 public void setType(Integer type) {
  this.type = type;
 }

 public MarketChatRecord getChatRecord() {
  return marketChatRecord;
 }
 public void setChatRecord(MarketChatRecord chatRecord) {
  this.marketChatRecord = chatRecord;
 }

 public Object getExt() {
  return ext;
 }

 public void setExt(Object ext) {
  this.ext = ext;
 }

 @Override
 public String toString() {
  return "Message{" +
    "type=" + type +
    ", marketChatRecord=" + marketChatRecord +
    ", ext=" + ext +
    '}';
 }

}

public class ChatHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
 private static final Logger log = LoggerFactory.getLogger(WebSocketServer.class);


 /**
  * 用來保存所有的客戶端連接
  */
 private static ChannelGroup clients = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

 /**
  *當Channel中有新的事件消息會自動調用
  */
 @Override
 protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
  // 當接收到數據后會自動調用
  // 獲取客戶端發送過來的文本消息
  Gson gson = new Gson();
  log.info("服務器收到消息：{}",msg.text());
  System.out.println("接收到消息數據為：" + msg.text());
  Message message = gson.fromJson(msg.text(), Message.class); 
//根據業務要求進行消息處理
  switch (message.getType()) {
   // 處理客戶端連接的消息
   case 0:
    // 建立用戶與通道的關聯
   // 處理客戶端發送好友消息
    break;
   case 1:
   // 處理客戶端的簽收消息
    break;
   case 2:
    // 將消息記錄設置為已讀
    break;
   case 3:
    // 接收心跳消息
    break;
   default:
    break;
  }

 }

 // 當有新的客戶端連接服務器之后，會自動調用這個方法
 @Override
 public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
  log.info("handlerAdded 被調用"+ctx.channel().id().asLongText());
  // 添加到channelGroup 通道組
  UserChannelMap.getChannelGroup().add(ctx.channel());
//  clients.add(ctx.channel());
 }

 @Override
 public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
  log.info("{異常:}"+cause.getMessage());
  // 刪除通道
  UserChannelMap.getChannelGroup().remove(ctx.channel());
  UserChannelMap.removeByChannelId(ctx.channel().id().asLongText());
  ctx.channel().close();
 }

 @Override
 public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
  log.info("handlerRemoved 被調用"+ctx.channel().id().asLongText());
  //刪除通道
  UserChannelMap.getChannelGroup().remove(ctx.channel());
  UserChannelMap.removeByChannelId(ctx.channel().id().asLongText());
  UserChannelMap.print();
 }

}

public class HearBeatHandler extends ChannelInboundHandlerAdapter {

 @Override
 public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
  if(evt instanceof IdleStateEvent) {
   IdleStateEvent idleStateEvent = (IdleStateEvent)evt;

   if(idleStateEvent.state() == IdleState.READER_IDLE) {
    System.out.println("讀空閑事件觸發...");
   }
   else if(idleStateEvent.state() == IdleState.WRITER_IDLE) {
    System.out.println("寫空閑事件觸發...");
   }
   else if(idleStateEvent.state() == IdleState.ALL_IDLE) {
    System.out.println("---------------");
    System.out.println("讀寫空閑事件觸發");
    System.out.println("關閉通道資源");
    ctx.channel().close();
   }
  }
 }
}