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基于Java的WebSocket推送

2016-05-15 16:21  tony4geek  阅读(46889)  评论(7)  编辑  收藏  举报

WebSocket的主动推送

关于消息推送，现在的解决方案如轮询、长连接或者短连接，当然还有其他的一些技术框架，有的是客户端直接去服务端拿数据。
其实推送推送主要讲的是一个推的概念，WebSocket是一种主动推送消息的技术。

基于Java的WebSocket

这里主要是结合网上的例子实现下。

简单的客户端JavaScript

<!DOCTYPE html>
<html>
<head>
<title>Testing websockets</title>
</head>
<body>
  <div>
    <input type="submit" value="Start" onclick="start()" />
  </div>
  <div id="messages"></div>
  <script type="text/javascript">
    var webSocket =
      new WebSocket('ws://localhost:8080/wesocket/websocketTest');
    webSocket.onerror = function(event) {
      onError(event)
    };
 
    webSocket.onopen = function(event) {
      onOpen(event)
    };
 
    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;
    }
  </script>
</body>
</html>

服务端

package com.tony.websocket;

import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;

@ServerEndpoint("/websocketTest")
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");
	}
}

pom.xml 文件

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.tony</groupId>
	<artifactId>wesocket</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<dependencies>
		<dependency>
			<groupId>javax.websocket</groupId>
			<artifactId>javax.websocket-api</artifactId>
			<version>1.0-rc5</version>
			<scope>provided</scope>
		</dependency>
	</dependencies>
</project>

我这里用的是JDK是 jdk1.8.0_60 ，Tomcat用的是 apache-tomcat-7.0.64 。
1、建立连接

2、发送消息

3、服务端推送消息