DWR3实现服务器端向客户端精确推送消息

发布时间：2020-12-15 21:44:39 所属栏目：百科来源：网络整理

导读：我这种刚开始学习DWR的人来说要看懂真的蛮难。不过即便如此， http://www.blogjava.net/stevenjohn/archive/2012/07/07/382447.html这片文章还是给了我很大帮助，再次表示感谢，下面我将这两天的研究详细记录下来备忘，也希望能帮助到像我一样的人。只写过程

我这种刚开始学习DWR的人来说要看懂真的蛮难。不过即便如此， http://www.blogjava.net/stevenjohn/archive/2012/07/07/382447.html这片文章还是给了我很大帮助，再次表示感谢，下面我将这两天的研究详细记录下来备忘，也希望能帮助到像我一样的人。只写过程，不写原理（不是不写，而是有些地方我也不太懂），下面开始：

第一、在项目中引入dwr.jar，然后在web.xml中进行配置，配置如下：

Java代码

<servlet>
<servlet-name>dwr-invoker</servlet-name>
<servlet-class>
org.directwebremoting.servlet.DwrServlet
</servlet-class>
<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>

        <servlet-name>dwr-invoker</servlet-name>

        <servlet-class>

            org.directwebremoting.servlet.DwrServlet

        </servlet-class>

        <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>

第二：在web.xml的同级目录下新建dwr.xml文件，内容如下

Java代码

<!DOCTYPEdwrPUBLIC
"-//GetAheadLimited//DTDDirectWebRemoting3.0//EN"
"http://getahead.org/dwr/dwr30.dtd">
<dwr>
<alow>
<createcreator="new"javascript="MessagePush">
<paramname="class"value="com.huatech.messageremind.service.MessagePush"/>
</create>
<createcreator="new"javascript="TestPush">
<paramname="class"value="com.huatech.messageremind.service.Test"/>
</create>
</alow>
</dwr>

<!DOCTYPE dwr PUBLIC
     "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN"
     "http://getahead.org/dwr/dwr30.dtd">

<dwr>
     <alow>
          <create creator="new" javascript="MessagePush">
            <param name="class" value="com.huatech.messageremind.service.MessagePush"/>
         </create>
          <create creator="new" javascript="TestPush">
            <param name="class" value="com.huatech.messageremind.service.Test"/>
         </create>
     </alow>
</dwr>

这个是dwr的基本配置，MessagePush在页面的javascript中使用，这个是对被推送页面开放的java类，Test是对推送页面开放的java类。场景：管理员后台登陆，发布一条消息，通过Test推送到后台，后台通过MessagePush推送给指定的用户，当然，至于怎么找到指定的用户，下面会说。

第三，被推送的页面代码

Java代码

<%@pagelanguage="java"import="java.util.*"pageEncoding="utf-8"%>
<%
Stringpath=request.getContextPath();
StringbasePath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01Transitional//EN">
<html>
<head>
<basehref="<%=basePath%>">
<title>DWRDEMO</title>
<metahttp-equiv="pragma"content="no-cache">
<metahttp-equiv="cache-control"content="no-cache">
<metahttp-equiv="expires"content="0">
<metahttp-equiv="keywords"content="keyword1,keyword2,keyword3">
<metahttp-equiv="description"content="Thisismypage">
</head>
<scripttype='text/javascript'src='dwr/engine.js'></script>
<scripttype='text/javascript'src='dwr/util.js'></script>
<scripttype="text/javascript"src="dwr/interface/MessagePush.js"></script>
<scripttype="text/javascript">
//通过该方法与后台交互，确保推送时能找到指定用户
functiononPageLoad(){
varuserId='${userinfo.humanid}';
MessagePush.onPageLoad(userId);
}
//推送信息
functionshowMessage(autoMessage){
alert(autoMessage);
}
</script>
<bodyonload="onPageLoad();dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true);;">
ThisismyDWRDEOMpage.<hr>
<br>
<divid="DemoDiv">demo</div>
</body>
</html>

<%@ 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,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.humanid}';
            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>

以上代码的简单解释：

页面页面onload的3个函数都是必须的，后两个是dwr的，第一个是将登录用户的userid与对应的scriptSession进行处理，以便精确推送的时候能找到推送对象

第四 MessagePush类中实现的方法如下：

Java代码

publicvoidonPageLoad(StringuserId){
ScriptSessionscriptSession=WebContextFactory.get().getScriptSession();
scriptSession.setAttribute(userId,userId);
DwrScriptSessionManagerUtildwrScriptSessionManagerUtil=newDwrScriptSessionManagerUtil();
try{
dwrScriptSessionManagerUtil.init();
System.out.println("cacaca");
}catch(ServletExceptione){
e.printStackTrace();
}
}

      public void onPageLoad(String userId) {

        ScriptSession scriptSession = WebContextFactory.get().getScriptSession();

        scriptSession.setAttribute(userId,userId);

        DwrScriptSessionManagerUtil dwrScriptSessionManagerUtil = new DwrScriptSessionManagerUtil();

        try {

               dwrScriptSessionManagerUtil.init();
               System.out.println("cacaca");

        } catch (ServletException e) {

               e.printStackTrace();

        }

 }

里面对应的DwrScriptSessionManagerUtil 对应如下：

Java代码

importjavax.servlet.ServletException;
importjavax.servlet.http.HttpSession;
importorg.directwebremoting.Container;
importorg.directwebremoting.ServerContextFactory;
importorg.directwebremoting.WebContextFactory;
importorg.directwebremoting.event.ScriptSessionEvent;
importorg.directwebremoting.event.ScriptSessionListener;
importorg.directwebremoting.extend.ScriptSessionManager;
importorg.directwebremoting.servlet.DwrServlet;
publicclassDwrScriptSessionManagerUtilextendsDwrServlet{
privatestaticfinallongserialVersionUID=-7504612622407420071L;
publicvoidinit()throwsServletException{
Containercontainer=ServerContextFactory.get().getContainer();
ScriptSessionManagermanager=container.getBean(ScriptSessionManager.class);
ScriptSessionListenerlistener=newScriptSessionListener(){
publicvoidsessionCreated(ScriptSessionEventev){
HttpSessionsession=WebContextFactory.get().getSession();
StringuserId=((User)session.getAttribute("userinfo")).getHumanid()+"";
System.out.println("aScriptSessioniscreated!");
ev.getSession().setAttribute("userId",userId);
}
publicvoidsessionDestroyed(ScriptSessionEventev){
System.out.println("aScriptSessionisdistroyed");
}
};
manager.addScriptSessionListener(listener);
}
}

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;

public class DwrScriptSessionManagerUtil extends DwrServlet{

    private static final long serialVersionUID = -7504612622407420071L;

    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 =((User) session.getAttribute("userinfo")).getHumanid()+"";
                         System.out.println("a ScriptSession is created!");
                         ev.getSession().setAttribute("userId",userId);
                  }
                  public void sessionDestroyed(ScriptSessionEvent ev) {
                         System.out.println("a ScriptSession is distroyed");
                  }
           };
           manager.addScriptSessionListener(listener);
    }
}

第五推送页面代码：

Java代码

<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-8"%>
<%
Stringpath=request.getContextPath();
StringbasePath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01Transitional//EN">
<html>
<head>
<basehref="<%=basePath%>">
<title>MyJSP'MyJsp.jsp'startingpage</title>
<metahttp-equiv="pragma"content="no-cache">
<metahttp-equiv="cache-control"content="no-cache">
<metahttp-equiv="expires"content="0">
<metahttp-equiv="keywords"content="keyword1,keyword3">
<metahttp-equiv="description"content="Thisismypage">
<scripttype="text/javascript"src="<%=request.getContextPath()%>/js/jquery-1.5.1.js"></script>
<scripttype='text/javascript'src='dwr/engine.js'></script>
<scripttype='text/javascript'src='dwr/util.js'></script>
<scripttype='text/javascript'src='dwr/interface/TestPush.js'></script>
<scripttype="text/javascript">
functiontest(){
varmsg=document.getElementById("msgId").value;
//msg={msgId:'1',context:$("#msgContext").val()};
TestPush.sendMessageAuto(msg,"哈哈哈");
}
</script>
</head>
<body>
id    :<inputtype="text"name="msgId"id="msgId"/><br/>
<inputtype="button"value="Send"onclick="test()"/>
</body>
</html>

<%@ 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,keyword3">
	<meta http-equiv="description" content="This is my page">
	<script type="text/javascript" src="<%=request.getContextPath() %>/js/jquery-1.5.1.js"></script>
	<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 test() {
		var msg = document.getElementById("msgId").value;
		//msg = {msgId: '1',context: $("#msgContext").val()};
		TestPush.sendMessageAuto(msg,"哈哈哈");
		
	}
	</script>
  </head>
  
  <body>
    id&nbsp;&nbsp;&nbsp;&nbsp;: <input type="text" name="msgId" id="msgId" /> <br />
   
   	<input type="button" value="Send" onclick="test()"  />
   	
  </body>
</html>

第六：精确推送要实现的代码：

Java代码

publicclassTest{
publicvoidsendMessageAuto(Stringuserid,Stringmessage){
finalStringuserId=userid;
finalStringautoMessage=message;
Browser.withAllSessionsFiltered(newScriptSessionFilter(){
publicbooleanmatch(ScriptSessionsession){
if(session.getAttribute("userId")==null)
returnfalse;
else
return(session.getAttribute("userId")).equals(userId);
}
},newRunnable(){
privateScriptBufferscript=newScriptBuffer();
publicvoidrun(){
script.appendCall("showMessage",autoMessage);
Collection<ScriptSession>sessions=Browser
.getTargetSessions();
for(ScriptSessionscriptSession:sessions){
scriptSession.addScript(script);
}
}
});
}
}

public class Test{
    public void sendMessageAuto(String userid,String message){
        
        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);
                }
            }
        });
    }
}

至此这个例子的代码都已经贴出来了，应该是可以跑通的，有问题的话可以给我留言。当然，要自己写个登录，然后把userId放到session里面，这个比较简单，就不贴代码了，有问题可以在http://download.csdn.net/detail/luojia_wang/5275588上下载原项目。我只是简单的做了一个能实现功能的例子，还有很多地方要研究，比如跟spring整合，还可能有很多优化，等我继续学习一下再说.

（编辑：李大同）

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