学习笔记，供大家参考
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1. 导入JAR包 javax.websocket-api

   <dependency><groupId>javax.websocket</groupId><artifactId>javax.websocket-api</artifactId><version>1.1</version><scope>provided</scope>
   </dependency>
   

2. 编写WebSocket.class

   package cn.bigchin.spark.app.ws;import cn.bigchin.spark.Spark;
   import cn.bigchin.spark.SparkConst;
   import cn.bigchin.spark.expand.event.SparkEvent;
   import com.jfinal.kit.Kv;
   import com.jfinal.kit.StrKit;
   import com.jfinal.log.Log;
   import javax.websocket.*;
   import javax.websocket.Session;
   import javax.websocket.server.PathParam;
   import javax.websocket.server.ServerEndpoint;import java.io.IOException;
   import java.util.concurrent.ConcurrentSkipListMap;/*** TODO:** @author 一川死水 (yichuan95@126.com)* @Date 2024/9/19*/
   @ServerEndpoint("/websocket/{id}")
   public class WebSocket {Log log = Log.getLog(WebSocket.class);private String id;//与某个客户端的连接会话，需要通过它来给客户端发送数据private Session session;//concurrent包的线程安全Set，用来存储每个客户端对应的MySocket对象private static ConcurrentSkipListMap<String, WebSocket> webSocketMap = new ConcurrentSkipListMap<>();@OnOpenpublic void onOpen(@PathParam("id") String id, Session session) throws IOException {this.session = session;this.id = id;webSocketMap.put(id, this);log.debug(String.format("用户:%s已连接", id));}@OnClosepublic void onClose(Session session) {log.debug(String.format("用户:%s已断开链接"));webSocketMap.remove(id);}@OnErrorpublic void onError(Session session, Throwable error) {error.printStackTrace();log.debug("链接异常", error);));}@OnMessagepublic void onMessage(Session session, String message) throws IOException {// 收到消息,根据自己的业务作实际处理判断是否在线，如原样发送回客户端session.getBasicRemote().sendText(message);}/*** TODO:群发自定义消息（建议使用此方法）** @param id      用户id id为null时 ，为群发* @param message 消息内容*/public static void sendMessage(String id, String message) throws IOException {for (String idKey : webSocketMap.keySet()) {if (StrKit.isBlank(id)) {webSocketMap.get(idKey).session.getAsyncRemote().sendText(message);} else {if (idKey.equals(id)) {webSocketMap.get(idKey).session.getAsyncRemote().sendText(message);}}}}
   }
   

3. 如果是在undertow 下启动,则要继续添加依赖,如果是tomcat环境下,可跳过这一步

    <!-- jfinal-undertow  --><dependency><groupId>com.jfinal</groupId><artifactId>jfinal-undertow</artifactId><version>2.0</version></dependency><!-- 开发 WebSockets 时开启下面的依赖 --><dependency><groupId>io.undertow</groupId><artifactId>undertow-websockets-jsr</artifactId><version>2.0.28.Final</version></dependency>
   

   然后在undertow启动添加websocket集成

    //configClass自行替换成自己的配置类UndertowServer server = UndertowServer.create(configClass);server.configWeb(webBuilder -> {webBuilder.addWebSocketEndpoint(WebSocket.class);});server.start();
   

4. 不拦截websocket的访问

   //在自己的配置类中添加拦截,
   //如果WebSocket 中的@ServerEndpoint配置地址有带.的,如@ServerEndpoint("/websocket.ws/{id}"),则无需添加拦截,因为带 "." 字符的 url 不会被 jfinal 框架当成 action,所以直接跳过了
   public void configHandler(Handlers me) {me.add(new UrlSkipHandler("^/websocket", false));
   }
   

5. 前端js代码

   let id='1'
   let webSocket = null;
   if (window.WebSocket) {if(Protocol == 'https'){websocket = new WebSocket('wss://' + host + '/websocket/' + id);}else{websocket = new WebSocket('ws://' + host + '/websocket/' + id);}      
   } else {   console.log("您的浏览器不支持WebSocket");return;
   }
   //打开事件
   webSocket.onopen = function (){console.log("WebSocket已打开");//webSocket.send("这是来自客户端的消息"+id+new Date());
   }
   //获得消息事件
   webSocket.onmessage = function (message){//收到消息,自行处理业务逻辑console.log(message)
   }
   //关闭事件
   webSocket.onclose = function (){console.log("Socket已关闭");
   }
   //发生了错误
   webSocket.onerror = function (){console.log("Socket发生了错误");
   }
   //发送消息
   function send(message) {websocket.send(message);
   }
   //当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口
   window.onbeforeunload = function () {websocket.close();
   }