DWR由服务器端向客户端推送消息

发布时间：2020-12-16 01:44:20 所属栏目：百科来源：网络整理

导读：实现步骤：第一、在项目中引入 dwr.jar ，然后在 web.xml 中进行配置，配置如下： servletservlet-namedwr-invoker/servlet-nameservlet-classorg.directwebremoting.servlet.DwrServlet/servlet-classinit-paramparam-namedebug/param-nameparam-valuetrue

实现步骤：

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

<servlet>
<servlet-name>dwr-invoker</servlet-name>
<servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
<init-param>
<param-name>debug</param-name>
<param-value>true</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>dwr-invoker</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>

第二：和同级目增加dwr.xml，内容如下

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

dwr的基本配置指向具体实现类，MessagePush在页面的javascript中使用（被推送者），Test推送者

第三，被推送的页面

<%@pagelanguage="java"import="java.util.*"pageEncoding="utf-8"%>
<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01Transitional//EN">
<html>
<head>
<metahttp-equiv="cache-control"content="no-cache">
</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">
functiononPageLoad(){
varuserId='${userinfo.id}';
MessagePush.onPageLoad(userId);
}
//推送信息
functionshowMessage(mgs){
alert(mgs);
}
</script>
<bodyonload="onPageLoad();dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true);">
<divid="DemoDiv">helloworld</div>
</body>
</html>

注意：页面加载时加载的函数setActiveReverseAjax和setNotifyServerOnPageUnload是dwr的，onPageLoad是将登陆的用户和scriptSession进行绑定，为以后的推送做准备。

第四 MessagePush类：

publicvoidonPageLoad(StringuserId){
ScriptSessionscriptSession=WebContextFactory.get().getScriptSession();
scriptSession.setAttribute(userId,userId);
DwrSSessionUtilss=newDwrSSessionUtil();
try{
ss.init();
}catch(ServletExceptione){
e.printStackTrace();
}
}

第五：DwrSSessionUtil ：

publicclassDwrSSessionUtilextendsDwrServlet{
publicvoidinit()throwsServletException{
Containercontainer=ServerContextFactory.get().getContainer();
ScriptSessionManagermanager=container.getBean(ScriptSessionManager.class);
ScriptSessionListenerlistener=newScriptSessionListener(){
publicvoidsessionCreated(ScriptSessionEventev){
HttpSessionsession=WebContextFactory.get().getSession();
StringuserId=((User)session.getAttribute("userinfo")).getId()+"";
System.out.println("aScriptSessioniscreated!");
ev.getSession().setAttribute("userId",userId);
}
publicvoidsessionDestroyed(ScriptSessionEventev){
System.out.println("aScriptSessionisdistroyed");
}
};
manager.addScriptSessionListener(listener);
}
}

第五 JSP页面：

<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-8"%>
<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01Transitional//EN">
<html>
<head>
<metahttp-equiv="cache-control"content="no-cache">
<metahttp-equiv="expires"content="0"
<scripttype="text/javascript"src="js/jquery-2.1.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;
TestPush.sendMessageAuto(msg,"收到没");
}
</script>
</head>
<body>
id：<inputtype="text"name="msgId"id="msgId"/><br/>
<inputtype="button"value="你好"onclick="test()"/>
</body>
</html>

第六：推送代码：

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(){
privateScriptBuffers=newScriptBuffer();
publicvoidrun(){
s.appendCall("showMessage",autoMessage);
Collection<ScriptSession>sessions=Browser.getTargetSessions();
for(ScriptSessionscriptSession:sessions){
scriptSession.addScript(s);
}
}
});
}
}

（编辑：李大同）

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