1、在工程中引入dwr.jar，之后修改配置web.xml文件，添加配置具体代码如下：
1<servlet> 2 <servlet-name>dwr-invoker</servlet-name> 3 <servlet-class> 4 org.directwebremoting.servlet.DwrServlet 5 </servlet-class> 6 <init-param> 7 <param-name>crossDomainSessionSecurity</param-name> 8 <param-value>false</param-value> 9 </init-param> 10 <init-param> 11 <param-name>allowScriptTagRemoting</param-name> 12 <param-value>true</param-value> 13 </init-param> 14 <init-param> 15 <param-name>classes</param-name> 16 <param-value>java.lang.Object</param-value> 17 </init-param> 18 <init-param> 19 <param-name>activeReverseAjaxEnabled</param-name> 20 <param-value>true</param-value> 21 </init-param> 22 <init-param> 23 <param-name>initApplicationScopeCreatorsAtStartup</param-name> 24 <param-value>true</param-value> 25 </init-param> 26 <init-param> 27 <param-name>maxWaitAfterWrite</param-name> 28 <param-value>3000</param-value> 29 </init-param> 30 <init-param> 31 <param-name>debug</param-name> 32 <param-value>true</param-value> 33 </init-param> 34 <init-param> 35 <param-name>logLevel</param-name> 36 <param-value>WARN</param-value> 37 </init-param> 38 </servlet>
2、在web.xml统计目录下新增dwr.xml文件，具体内容如下：
1<!DOCTYPE dwr PUBLIC 2 "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN" 3 "http://getahead.org/dwr/dwr30.dtd"> 4 <dwr> 5 <alow> 6 <create creator="new" javascript="MessagePush"> 7 <param name="class" value="com.yoodb.service.MessagePush"/> 8 </create> 9 <create creator="new" javascript="TestPush"> 10 <param name="class" value="com.yoodb.service.TestPush"/> 11 </create> 12 </alow> 13 </dwr>
MessagePush在页面的javascript中使用，com.yoodb.service.MessagePush实现了想要调用的方法，其中MessagePush.java对被推送页面开放的java类，Test.java是对推送页面开放的java类。在javascript中使用MessagePush.java类中实现的方法，即可在dwr中调用。
3、引入JavaScript文件，具体如下：
1<script type="text/javascript" src="<%=basepath%>dwr/engine.js"></script> 2<script type="text/javascript" src="<%=basepath%>dwr/util.js"></script> 3<script type="text/javascript" src="<%=basepath%>dwr/interface/MessagePush.js"></script>
注意：
1)dwr.xml配置的javascript中engine.js和util.js是必须引入的文件。
2)在任何一个用户登录的时候，都需要将其userId或者其他唯一性标识放入session中，我放的是userId，这里就以userId为唯一性标识。
3)在载入想推送的页面时，需要onload一个我在MessagePush类中实现的方法，当然了，需要使用dwr调用
被推送html页面具体内容代码如下：
1<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> 2<% 3String path = request.getContextPath(); 4String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 5%> 6<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 7<html> 8 <head> 9 <base href="<%=basePath%>"> 10 <title>DWR DEMO</title> 11 <meta http-equiv="pragma" content="no-cache"> 12 <meta http-equiv="cache-control" content="no-cache"> 13 <meta http-equiv="expires" content="0"> 14 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 15 <meta http-equiv="description" content="This is my page"> 16 </head> 17 <script type='text/javascript' src='dwr/engine.js'></script> 18 <script type='text/javascript' src='dwr/util.js'></script> 19 <script type="text/javascript" src="dwr/interface/MessagePush.js"></script> 20 21 <script type="text/javascript"> 22 //通过该方法与后台交互，确保推送时能找到指定用户 23 function onPageLoad(){ 24 var userId = '${userinfo.userId}'; 25 MessagePush.onPageLoad(userId); 26 } 27 //推送信息 28 function showMessage(autoMessage){ 29 alert(autoMessage); 30 } 31 </script> 32 <body onload="onPageLoad();dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true);;"> 33 This is my DWR DEOM page. <hr> 34 <br> 35 <div id="DemoDiv">demo</div> 36 </body> 37</html>
其中MessagePush.java文件中实现方法，如下：
1public class MessagePush{ 2 public void onPageLoad(String userId) { 3 ScriptSession scriptSession = WebContextFactory.get().getScriptSession(); 4 scriptSession.setAttribute(userId, userId); 5 DwrScriptSessionManagerUtil dwrScriptSessionManagerUtil = new DwrScriptSessionManagerUtil(); 6 try { 7 dwrScriptSessionManagerUtil.init(); 8 System.out.println("cacaca"); 9 } catch (ServletException e) { 10 e.printStackTrace(); 11 } 12 } 13}
对于onPageLoad()方法中DwrScriptSessionManagerUtil类的实现，具体如下：
1import javax.servlet.ServletException; 2import javax.servlet.http.HttpSession; 3 4import org.directwebremoting.Container; 5import org.directwebremoting.ServerContextFactory; 6import org.directwebremoting.WebContextFactory; 7import org.directwebremoting.event.ScriptSessionEvent; 8import org.directwebremoting.event.ScriptSessionListener; 9import org.directwebremoting.extend.ScriptSessionManager; 10import org.directwebremoting.servlet.DwrServlet; 11 12public class DwrScriptSessionManagerUtil extends DwrServlet{ 13 14 private static final long serialVersionUID = -7504612622407420071L; 15 16 public void init()throws ServletException { 17 18 Container container = ServerContextFactory.get().getContainer(); 19 ScriptSessionManager manager = container.getBean(ScriptSessionManager.class); 20 ScriptSessionListener listener = new ScriptSessionListener() { 21 public void sessionCreated(ScriptSessionEvent ev) { 22 HttpSession session = WebContextFactory.get().getSession(); 23 24 String userId =((User) session.getAttribute("userinfo")).getHumanid()+""; 25 System.out.println("a ScriptSession is created!"); 26 ev.getSession().setAttribute("userId", userId); 27 } 28 public void sessionDestroyed(ScriptSessionEvent ev) { 29 System.out.println("a ScriptSession is distroyed"); 30 } 31 }; 32 manager.addScriptSessionListener(listener); 33 } 34}
4、推送html页面具体内容代码如下：
1<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> 2<% 3String path = request.getContextPath(); 4String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 5%> 6<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 7<html> 8 <head> 9 <base href="<%=basePath%>"> 10 <title>My JSP 'MyJsp.jsp' starting page</title> 11 <meta http-equiv="pragma" content="no-cache"> 12 <meta http-equiv="cache-control" content="no-cache"> 13 <meta http-equiv="expires" content="0"> 14 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 15 <meta http-equiv="description" content="This is my page"> 16 <script type='text/javascript' src='dwr/engine.js'></script> 17 <script type='text/javascript' src='dwr/util.js'></script> 18 <script type='text/javascript' src='dwr/interface/TestPush.js'></script> 19 20 <script type="text/javascript"> 21 22 function testPush() { 23 var msg = document.getElementById("msgId").value; 24 TestPush.sendMessageAuto(msg,"www.yoodb.com"); 25 26 } 27 </script> 28 </head> 29 30 <body> 31 id值: <input type="text" name="msgId" id="msgId" /> <br /> 32 <input type="button" value="Send" onclick="testPush()" /> 33 </body> 34</html>
其中TeshPush.java文件，具体内容如下：
1public class TestPush{ 2 public void sendMessageAuto(String userid, String message){ 3 4 final String userId = userid; 5 final String autoMessage = message; 6 Browser.withAllSessionsFiltered(new ScriptSessionFilter() { 7 public boolean match(ScriptSession session){ 8 if (session.getAttribute("userId") == null) 9 return false; 10 else 11 return (session.getAttribute("userId")).equals(userId); 12 } 13 }, new Runnable(){ 14 15 private ScriptBuffer script = new ScriptBuffer(); 16 17 public void run(){ 18 19 script.appendCall("showMessage", autoMessage); 20 21 Collection<ScriptSession> sessions = Browser 22 23 .getTargetSessions(); 24 25 for (ScriptSession scriptSession : sessions){ 26 scriptSession.addScript(script); 27 } 28 } 29 }); 30 } 31}