JAVA集成WebSocket,实现服务器与客户端握手

r囧r小猫 2022-05-29 11:42 502阅读 0赞

###                                       WebSocket实现服务器与客户端握手 ###

自学的WebSocket途中遇到很多坑，希望需要使用的朋友可以少走弯路，

使用的环境:tomcat7.0,mysql,springMvc,spring,Mybatis

主要使用2个jar包 这2个jar包在tomcat7的 lib文件夹里面有

catalina.jar        websocket-api.jar

其他jar包截图如下

![70][]

本章实例中,实现了客户端之间的通信和服务器响应数据给客户端

1.客户端之间的通信，打开2个浏览器模仿QQ聊天功能

![70 1][]![70 2][]

2.服务器与客户端之间的通信

当数据库信息发生改变时候，服务器把最新的数据响应给客户端

![70 3][]

这是数据没改变的时候的

![70 4][]

当数据库发生改变时候，服务器把最新的数据推送给客户端

![70 5][]![70 6][]

没改变的时候，服务器不会推送数据

![70 7][]![70 8][]

主要类3个

![70 9][]

GetHttpSession用与在MyWebSocket类中获取HttpSession对象

package ljm.web;
    import javax.servlet.http.HttpSession;
    import javax.websocket.HandshakeResponse;
    import javax.websocket.server.HandshakeRequest;
    import javax.websocket.server.ServerEndpointConfig;
    
    public class GetHttpSession extends ServerEndpointConfig.Configurator
    {
    	@Override
    	public void modifyHandshake(ServerEndpointConfig config,
    	HandshakeRequest request,HandshakeResponse response){
    		HttpSession httpSession = (HttpSession)request.getHttpSession();
    		config.getUserProperties().put(HttpSession.class.getName(),httpSession);
    }
    }

MyWebSocket用实现服务器与客户端的通信

package ljm.web;
    import java.io.IOException;
    import java.util.concurrent.CopyOnWriteArraySet;
    import javax.servlet.http.HttpSession;
    import javax.websocket.EndpointConfig;
    import javax.websocket.OnClose;
    import javax.websocket.OnError;
    import javax.websocket.OnMessage;
    import javax.websocket.OnOpen;
    import javax.websocket.Session;
    import javax.websocket.server.ServerEndpoint;
    
    import org.springframework.web.context.ContextLoader;
    
    import ljm.service.UserService;
    
    @ServerEndpoint(value="/chat",configurator=GetHttpSession.class)
    public class MyWebSocket {
    	private UserService userService = (UserService) ContextLoader.getCurrentWebApplicationContext().getBean("userService");  
    	
    	//静态变量，用来记录当前在线连接数。应该把它设计成线程安全的。
        private static int onlineCount = 0;
        //更新数据的线程
        RefreshThread thread =null;
        //concurrent包的线程安全Set，用来存放每个客户端对应的MyWebSocket对象。若要实现服务端与单一客户端通信的话，可以使用Map来存放，其中Key可以为用户标识
        private static CopyOnWriteArraySet<MyWebSocket> webSocketSet = new CopyOnWriteArraySet<MyWebSocket>();
         
        //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;
         
        /**
         * 连接建立成功调用的方法
         * @param session  可选的参数。session为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
         * @throws Exception 
         */
        @OnOpen
        public void onOpen(Session session,EndpointConfig config) throws Exception{	
        	Integer age=userService.findUserAge(1);
        	System.out.println(age);
            this.session = session;
            webSocketSet.add(this);
            HttpSession se= (HttpSession) config.getUserProperties().get(HttpSession.class.getName());
           se.setAttribute("userId", 1);
            thread=new RefreshThread(session,se);
            thread.start();
            addOnlineCount();           //在线数加1
            System.out.println("有新连接加入！当前在线人数为" + getOnlineCount());
        }
         
        /**
         * 连接关闭调用的方法
         */
        @OnClose
        public void onClose(){
        	thread.stopThread();
            webSocketSet.remove(this);  //从set中删除
            subOnlineCount();           //在线数减1    
            System.out.println("有一连接关闭！当前在线人数为" + getOnlineCount());
        }
         
        /**
         * 收到客户端消息后调用的方法
         * @param message 客户端发送过来的消息
         * @param session 可选的参数
         */
        @OnMessage
        public void onMessage(String message, Session session) {
            System.out.println("来自客户端的消息:" + message);
             
            //群发消息
            for(MyWebSocket item: webSocketSet){             
                try {
                    item.sendMessage(message);
                } catch (IOException e) {
                    e.printStackTrace();
                    continue;
                }
            }
        }
         
        /**
         * 发生错误时调用
         * @param session
         * @param error
         */
        @OnError
        public void onError(Session session, Throwable error){
            System.out.println("发生错误");
            error.printStackTrace();
        }
         
        /**
         * 这个方法与上面几个方法不一样。没有用注解，是根据自己需要添加的方法。
         * @param message
         * @throws IOException
         */
        public void sendMessage(String message) throws IOException{
            //同步
        	this.session.getBasicRemote().sendText(message);
            //异步this.session.getAsyncRemote().sendText(message);
        }
        public static synchronized int getOnlineCount() {
            return onlineCount;
        }
     
        public static synchronized void addOnlineCount() {
            MyWebSocket.onlineCount++;
        }
         
        public static synchronized void subOnlineCount() {
            MyWebSocket.onlineCount--;
        }
        
    }

RefreshThread线程用于查询数据库有没有新的通知信息

package ljm.web;
    import javax.servlet.http.HttpSession;
    import javax.websocket.Session;
    
    import org.springframework.web.context.ContextLoader;
    
    import ljm.service.UserService;
    public class RefreshThread extends Thread {
    	  private Session session;
    	  private Integer currentAge;
    	  private HttpSession se;
    	  UserService userService;
    	  private volatile boolean stop = false;
    	  //关闭线程
    	  public void stopThread() {
    			 this.stop = true;
    		}	
    	  public RefreshThread(Session session,HttpSession se) throws Exception {
    		  userService = (UserService) ContextLoader.getCurrentWebApplicationContext().getBean("userService");  
    	        this.session = session;
    	        this.se=se;
    	        currentAge =userService.findUserAge((Integer) se.getAttribute("userId")) ;//此时是0条最新消息
    	    }
    	@Override
    	public void run() {
    		Integer age=null;
    		while (true) {
    			try {
    				Integer id=(Integer) se.getAttribute("userId");
    				age=userService.findUserAge(id);
    					if(age!=currentAge){
    					session.getBasicRemote().sendText(age+"");
    					currentAge=age;
    					}
    				  //一秒刷新一次
                    Thread.sleep(1000);
    			} catch (Exception e) {
    				e.printStackTrace();
    			}
    			
    	}
    	}	
    }

其次就是配置要通讯的JSP页面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    <%
    String path = request.getContextPath();
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
    %>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <base href="<%=basePath%>">
        
        <title>My JSP 'index.jsp' starting page</title>
    	<meta http-equiv="pragma" content="no-cache">
    	<meta http-equiv="cache-control" content="no-cache">
    	<meta http-equiv="expires" content="0">    
    	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    	<meta http-equiv="description" content="This is my page">
      </head>
     <body>
         Welcome<br/>
        <input id="text" type="text" /><button onclick="send()">Send</button>    <button onclick="closeWebSocket()">Close</button>
        <div id="message">
        </div>
      </body>
       
      <script type="text/javascript">
          var websocket = null;
           
          //判断当前浏览器是否支持WebSocket
          if('WebSocket' in window){
              websocket = new WebSocket("ws://localhost:8080/webSocketDemo/chat");
          }
          else{
              alert('Not support websocket');
          }
          //连接发生错误的回调方法
          websocket.onerror = function(){
              setMessageInnerHTML("error");
          };
           
          //连接成功建立的回调方法
          websocket.onopen = function(event){
              setMessageInnerHTML("open");
          };
          //接收到消息的回调方法
          websocket.onmessage = function(event){
              setMessageInnerHTML(event.data);
          };
           
          //连接关闭的回调方法
          websocket.onclose = function(){
              setMessageInnerHTML("close");
          };
           
          //监听窗口关闭事件，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，server端会抛异常。
          window.onbeforeunload = function(){
              websocket.close();
          };
          //将消息显示在网页上
          function setMessageInnerHTML(innerHTML){
              document.getElementById('message').innerHTML += innerHTML + '<br/>';
          }
           
          //关闭连接
          function closeWebSocket(){
              websocket.close();
          }
           
          //发送消息
          function send(){
              var message = document.getElementById('text').value;
              websocket.send(message);
          }
      </script>
    </html>

注意事项

![70 10][]

[70]: /images/20220529/46ec2a52a62f4a819825ae5be53f73fb.png
[70 1]: https://img-blog.csdn.net/2018032300475232?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21pbmcxOTk1MTIyNA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 2]: /images/20220529/d34d769d21d64202b4d6eb3b65c418b1.png
[70 3]: /images/20220529/8ce571d326d44098802c7660f54680bb.png
[70 4]: /images/20220529/08cd59a5c51749f3af530b7573b9117b.png
[70 5]: https://img-blog.csdn.net/20180323005355577?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21pbmcxOTk1MTIyNA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 6]: /images/20220529/8e0d6b6e3e6b475790fbdbdd655d0937.png
[70 7]: https://img-blog.csdn.net/20180323005505316?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21pbmcxOTk1MTIyNA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 8]: /images/20220529/148ff7811d464a35921f228b9d38be2a.png
[70 9]: /images/20220529/69d306b6fbcb4a17b738bb32f97ad2de.png
[70 10]: /images/20220529/d537346d75b1446089023c7b745bf25d.png