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

@Component
public class WebSocketConfig {

  @Bean
  public ServerEndpointExporter serverEndpointExporter() {

    return new ServerEndpointExporter();
  }
}

@Component
@ServerEndpoint("/webSocket")
@Slf4j
public class WebSocket {

  private Session session;

  private static CopyOnWriteArraySet<WebSocket> webSockets = new CopyOnWriteArraySet<>();

  private MessageVO messageVO = new MessageVO();

  @OnOpen
  public void onOpen(Session session) {
    this.session = session;
    webSockets.add(this);


    messageVO.setType(1);
    messageVO.setUserNum(webSockets.size());
    messageVO.setMessage("有新的连接");

    ObjectMapper mapper = new ObjectMapper();

    String Json = "";
    try {
      Json = mapper.writeValueAsString(messageVO);
    } catch (Exception ex) {
      log.error(ex.getMessage());
    }

    this.sendMessage(Json);
    log.info("【websocket消息】有新的连接, 总数:{}", webSockets.size());
  }


  @OnClose
  public void onClose() {
    webSockets.remove(this);

    messageVO.setType(2);
    messageVO.setUserNum(webSockets.size());
    messageVO.setMessage("有用户离开");

    ObjectMapper mapper = new ObjectMapper();

    String Json = "";
    try {
      Json = mapper.writeValueAsString(messageVO);
    } catch (Exception ex) {
      log.error(ex.getMessage());
    }

    this.sendMessage(Json);


    log.info("【websocket消息】连接断开, 总数:{}", webSockets.size());
  }

  @OnMessage
  public void onMessage(String message) {

    messageVO.setType(3);
    messageVO.setUserNum(webSockets.size());
    messageVO.setMessage(message);

    ObjectMapper mapper = new ObjectMapper();

    String Json = "";
    try {
      Json = mapper.writeValueAsString(messageVO);
    } catch (Exception ex) {
      log.error(ex.getMessage());
    }

    this.sendMessage(Json);

    log.info("【websocket消息】收到客户端发来的消息:{}", message);
  }

  public void sendMessage(String message) {
    for (WebSocket webSocket : webSockets) {
      log.info("【websocket消息】广播消息, message={}", message);
      try {
        webSocket.session.getBasicRemote().sendText(message);
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
}

<script type="application/javascript">
  var websocket = null;
  var cahtNum = $('.chat-num').text();
  if ('WebSocket' in window) {
    websocket = new WebSocket('ws://localhost:8080/chat/webSocket');

  } else {
    alert('该浏览器不支持websocket');
  }

  websocket.onopen = function (event) {
    console.log('websocket建立连接');
  }

  websocket.onclose = function (event) {
    console.log('websocket关闭连接');
  }

  websocket.onmessage = function (event) {
    console.log('websocket收到消息' + event.data);
    var result = $.parseJSON(event.data);
    if (result.type == 3) {
      var element = document.getElementById('message-template').innerHTML;
      $('.message-container').append(element);
      $(".message-content:last").html(result.message);
    }
    else {
      $('.chat-num').text(result.userNum);
    }

  }

  websocket.onerror = function (event) {
    console.log('websocket通信发生错误');

  }

  window.onbeforeunload = function (event) {
    websocket.close();
  }

  $('.send-message').click(function () {
    var message = $('.chat-message').val();
    if (message == "") {
      mdui.alert('请输入要发送的消息');
      return;
    }
    sendmessage(message);
    $('.chat-message').val("");
  })

  function sendmessage(message) {
    websocket.send(message);
  }
</script>