websocket——Firefox 无法建立到 ws://... 服务器的连接

快来打我* 2022-08-01 12:25 664阅读 0赞

页面访问java websocket服务时，出现异常，Firefox下的异常是：Firefox 无法建立到 ws://... 服务器的连接；

IE下的异常是：WebSocket Error: Incorrect HTTP response. Status code 404, Not Found

环境是：apache-tomcat-7.0.62、jdk1.7.0\_67、@ServerEndpoint("/websocket")这种声明式写法

我的排查步骤：

1、tomcat的JAVA\_HOME指向jdk7

2、Firefox参数调整，据说默认是关闭websocket的，但是我的版本是38.0.6，没有关闭

3、web.xml头部改为<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app\_3\_0.xsd" version="3.0">

4、最后发现，是由于我引入了一个javax.websocket-api.jar放到了WEB-INF/lib/下面，可能跟tomcat7的websocket-api.jar有冲突。

去掉javax.websocket-api.jar后异常消失

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="UTF-8">
    <title>Testing websocket</title>
    </head>
    <body>
    	<div>
    		<input type="submit" value="Start" οnclick="start()" />
    		<input type="button" value="Stop" οnclick="stop()" />
    	</div>
    	<div id="messages"></div>
    	<script type="text/javascript">
    		console.log(window.WebSocket);
    		var webSocket = new WebSocket('ws://127.0.0.1:8088/WebModule/websocket');
    
    		webSocket.onerror = function(event) {
    			onError(event)
    		};
    
    		webSocket.onopen = function(event) {
    			onOpen(event)
    		};
    
    		/* webSocket.onclose = function(event){
    			alert("要离开了？");
    		}; */
    		
    		webSocket.onmessage = function(event) {
    			onMessage(event)
    		};
    
    		function onMessage(event) {
    			document.getElementById('messages').innerHTML += '<br />'
    					+ event.data;
    		}
    
    		function onOpen(event) {
    			document.getElementById('messages').innerHTML = 'Connection established';
    		}
    
    		function onError(event) {
    			alert(event.data);
    		}
    
    		function start() {
    			webSocket.send('hello');
    			return false;
    		}
    		
    		function stop() {
    			webSocket.send('bye bye!');
    			webSocket.close();
    		}
    	</script>
    </body>
    </html>

import java.io.IOException;
    
    import javax.websocket.OnClose;
    import javax.websocket.OnMessage;
    import javax.websocket.OnOpen;
    import javax.websocket.Session;
    import javax.websocket.server.ServerEndpoint;
    
    @ServerEndpoint("/websocket")
    public class WebSocketTest {
    
    	@OnMessage
    	public void onMessage(String message, Session session) throws IOException, InterruptedException{
    		// Print the client message for testing purposes
    	    System.out.println("Received: " + message);
    	   
    	    // Send the first message to the client
    	    session.getBasicRemote().sendText("This is the first server message");
    	   
    	    // Send 3 messages to the client every 5 seconds
    	    int sentMessages = 0;
    	    while(sentMessages < 3){
    	      Thread.sleep(5000);
    	      session.getBasicRemote().sendText("This is an intermediate server message. Count: " + sentMessages);
    	      sentMessages++;
    	    }
    	   
    	    // Send a final message to the client
    	    session.getBasicRemote().sendText("This is the last server message");
    	}
    	
    	@OnOpen 
    	public void onOpen(){
    		System.out.println("Client connected");
    	}
    	
    	@OnClose
    	public void onClose(){
    		System.out.println("Connection closed");
    	}
    	
    }