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最近项目要实现一个消息推送的功能，主要就是发送站内信或者系统主动推送消息给当前在线的用户。每次的消息内容保存数据库，方便用户下次登录后也能看到。如果当前用户在线，收到站内信就主动弹出提示。一开始想到的是前台定时轮询通过ajax查询是否有未读消息。但是这种对系统压力太大。然后网上查询dwr可以主动实时推送消息。现把实现代码贴出来，方便以后使用。
web.xml加入如下配置
<!-- dwr 实时推送 start-->
<servlet>
<servlet-name>dwr</servlet-name>
<servlet-class>org.directwebremoting.spring.DwrSpringServlet
</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/dwr.xml</param-value>
</init-param>
<init-param>
<param-name>crossDomainSessionSecurity</param-name>
<param-value>false</param-value>
</init-param>
<init-param>
<param-name>allowScriptTagRemoting</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>classes</param-name>
<param-value>java.lang.Object</param-value>
</init-param>
<init-param>
<param-name>activeReverseAjaxEnabled</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>initApplicationScopeCreatorsAtStartup</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>maxWaitAfterWrite</param-name>
<param-value>3000</param-value>
</init-param>
<init-param>
<param-name>debug</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>logLevel</param-name>
<param-value>WARN</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>dwr</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>
<!-- dwr 实时推送 end -->
web.xml同级目录下新建dwr.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN" "http://getahead.org/dwr/dwr30.dtd">
<dwr>
<!-- dwr 实时推送 end-->
<create creator="new" javascript="MessagePush">
<param name="class" value="com.xsw.dwrMsg.service.MessagePush"/>
</create>
<create creator="new" javascript="TestPush">
<param name="class" value="com.xsw.dwrMsg.service.TestPush"/>
</create>
<!-- dwr 实时推送 end-->
</allow>
</dwr>
MessagePush类
/**
* 版权所有(C) 2016 xsw
* @author xsw
* @date 2017-6-23 下午05:38:43
*/
package com.xsw.dwrMsg.service;
import javax.servlet.ServletException;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.WebContextFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* @ClassName: MessagePush
* @Description: TODO()
* @author xsw
* @date 2017-6-23 下午05:38:43
*
*/
public class MessagePush {
private static Logger logger = LoggerFactory.getLogger(MessagePush.class);
public void onPageLoad(String userId) {
ScriptSession scriptSession = WebContextFactory.get().getScriptSession();
scriptSession.setAttribute(userId, userId);
DwrScriptSessionManagerUtil dwrScriptSessionManagerUtil = new DwrScriptSessionManagerUtil();
try {
dwrScriptSessionManagerUtil.init();
logger.info("["+userId+"]初始化，登录到推送的页面,站内信发送页面");
} catch (ServletException e) {
e.printStackTrace();
}
}
}
DwrScriptSessionManagerUtil工具类
/**
* 版权所有(C) 2016 xsw
* @author xsw
* @date 2017-6-26 下午06:31:46
*/
package com.xsw.dwrMsg.service;
import javax.servlet.ServletException;
import javax.servlet.http.HttpSession;
import org.directwebremoting.Container;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.event.ScriptSessionEvent;
import org.directwebremoting.event.ScriptSessionListener;
import org.directwebremoting.extend.ScriptSessionManager;
import org.directwebremoting.servlet.DwrServlet;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.ylink.eu.base.web.EUWebUtil;
/**
* @ClassName: DwrScriptSessionManagerUtil
* @Description: TODO()
* @author xsw
* @date 2017-6-26 下午06:31:46
*
*/
public class DwrScriptSessionManagerUtil extends DwrServlet{
private static final long serialVersionUID = -7504612622407420071L;
private static Logger logger = LoggerFactory.getLogger(DwrScriptSessionManagerUtil.class);
public void init()throws ServletException {
Container container = ServerContextFactory.get().getContainer();
ScriptSessionManager manager = container.getBean(ScriptSessionManager.class);
ScriptSessionListener listener = new ScriptSessionListener() {
public void sessionCreated(ScriptSessionEvent ev) {
//HttpSession session = WebContextFactory.get().getSession();
String userId =EUWebUtil.getUserContext().getAccountName();
logger.info("a ScriptSession is created!["+userId+"]");
ev.getSession().setAttribute("userId", userId);
}
public void sessionDestroyed(ScriptSessionEvent ev) {
logger.info("a ScriptSession is distroyed");
}
};
manager.addScriptSessionListener(listener);
}
}
TestPush类
/**
* 版权所有(C) 2016 xsw
* @author xsw
* @date 2017-6-26 下午05:42:51
*/
package com.xsw.dwrMsg.service;
import java.util.Collection;
import org.directwebremoting.Browser;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ScriptSessionFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* @ClassName: TestPush
* @Description: TODO()
* @author xsw
* @date 2017-6-26 下午05:42:51
*
*/
public class TestPush {
private static Logger logger = LoggerFactory.getLogger(TestPush.class);
public void sendMessageAuto(String userid, String message){
logger.info("发送消息["+message+"]给["+userid+"]");
final String userId = userid;
final String autoMessage = message;
Browser.withAllSessionsFiltered(new ScriptSessionFilter() {
public boolean match(ScriptSession session){
if (session.getAttribute("userId") == null)
return false;
else
return (session.getAttribute("userId")).equals(userId);
}
}, new Runnable(){
private ScriptBuffer script = new ScriptBuffer();
public void run(){
script.appendCall("showMessage", autoMessage);
Collection<ScriptSession> sessions = Browser
.getTargetSessions();
for (ScriptSession scriptSession : sessions){
scriptSession.addScript(script);
}
}
});
}
}
引入JavaScript文件，具体如下：
<script type="text/javascript" src="<%=basepath%>dwr/engine.js"></script> <script type="text/javascript" src="<%=basepath%>dwr/util.js"></script> <script type="text/javascript" src="<%=basepath%>dwr/interface/MessagePush.js"></script>
接收消息html页面具体内容代码如下：
<%@ 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>DWR DEMO</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>
<script type='text/javascript' src='dwr/engine.js'></script>
<script type='text/javascript' src='dwr/util.js'></script>
<script type="text/javascript" src="dwr/interface/MessagePush.js"></script>
<script type="text/javascript">
//通过该方法与后台交互，确保推送时能找到指定用户
function onPageLoad(){
var userId = '${userinfo.userId}';
MessagePush.onPageLoad(userId);
}
//推送信息
function showMessage(autoMessage){
alert(autoMessage);
}
</script>
<body onload="onPageLoad();dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true);;">
This is my DWR DEOM page. <hr>
<br>
<div id="DemoDiv">demo</div>
</body>
</html>
发送消息html页面具体内容代码如下：
<%@ 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 'MyJsp.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">
<script type='text/javascript' src='dwr/engine.js'></script>
<script type='text/javascript' src='dwr/util.js'></script>
<script type='text/javascript' src='dwr/interface/TestPush.js'></script>
<script type="text/javascript">
function testPush() {
var msg = document.getElementById("msgId").value;
TestPush.sendMessageAuto(msg,"www.xiongge.club");
}
</script>
</head>
<body>
id值: <input type="text" name="msgId" id="msgId" /> <br />
<input type="button" value="Send" onclick="testPush()" />
</body>
</html>
以上基本完成一个实时推送的功能。同时登陆用户A和B到系统，在A页面发送消息给B，B会alert出A发送的消息。以上代码仅供参考，优化扩展的方式有很多，欢迎交流。
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