dwr3+spring实现消息实时推送

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。

原文地址http://www.xiongge.club/1239.html