反向Ajax技术实例（二）

发布时间：2020-12-16 01:59:22 所属栏目：百科来源：网络整理

导读：1.创建一个Web Project项目，导入dwr.jar包。 2.修改web.xml文件如下： [c-sharp] view plain copy ?xmlversion= "1.0" encoding= "UTF-8" ? web-appversion= "2.5" xmlns= "http://java.sun.com/xml/ns/javaee" xmlns:xsi= "http://www.w3.org/2001/XMLSche

1.创建一个Web Project项目，导入dwr.jar包。

2.修改web.xml文件如下：

[c-sharp] 
   view plain 
   copy 
    
   
 <?xmlversion="1.0"encoding="UTF-8"?>
 <web-appversion="2.5"
 xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 <!--dwr核心servlet-->
 <listener>
 <listener-class>org.directwebremoting.servlet.DwrListener</listener-class>
 </listener>
 <servlet>
 <!--dwr核心servelt实现类-->
 <servlet-name>dwr</servlet-name>
 <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
 <!--设置dwr可调式-->
 <init-param>
 <param-name>debug</param-name>
 <param-value>true</param-value>
 </init-param>
 <!--设置ajax的反向技术-->
 <init-param>
 <param-name>activeReverseAjaxEnabled</param-name>
 <param-value>true</param-value>
 </init-param>
 <param-name>initApplicationScopeCreatorsAtStartip</param-name>
 <!--长连接时保持时间-->
 <param-name>maxWaitAfterWrite</param-name>
 <param-value>60</param-value>
 <load-on-startup>1</load-on-startup>
 </servlet>
 <servlet-mapping>
 <url-pattern>/dwr/*</url-pattern>
 </servlet-mapping>
 <welcome-file-list>
 <welcome-file>index.jsp</welcome-file>
 </welcome-file-list>
 </web-app>

3.创建一个SendingMessage.java类

copy

packagecom.yjpeng.dwr;

importjava.util.LinkedList;
importjava.util.List;
importjavax.naming.LinkLoopException;
importorg.directwebremoting.Browser;
importorg.directwebremoting.ScriptSession;
importorg.directwebremoting.ScriptSessions;
publicclassSendingMessage{
privateList<String>messages=newLinkedList<String>();
voidaddMessage(Stringmessage){
messages.add(message);
System.out.println("有客户请求消息:"+message);
Browser.withCurrentPage(newRunnable(){
voidrun(){
ScriptSessions.addFunctionCall("receiveMessage",messages);
}
});
}

4.创建dwr.xml文件

copy

<!DOCTYPEdwrPUBLIC

"-//GetAheadLimited//DTDDirectWebRemoting3.0//EN"
"http://getahead.org/dwr/dwr30.dtd">
<dwr>
<allow>
<createcreator="new"javascript="sendingMessage"scope="application">
<paramname="class"value="com.yjpeng.dwr.SendingMessage"></param>
</create>
</allow>
</dwr>

6.创建一个getMessage.jsp文件

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<script src="dwr/interface/sendingMessage.js"></script>
<script src="dwr/engine.js"></script>
<script src="dwr/util.js"></script>
<script type="text/javascript">
function sendMessage(){
var message = $("message").value;
sendingMessage.addMessage(message);
}

function receiveMessage(messages){
var chatlog = "";
for(var data in messages){
chatlog += "<div>" + messages[data] + "</div>";
}
dwr.util.setValue("list",chatlog,{escapeHtml:false});
}

</script>
</head>
<body onload="dwr.engine.setActiveReverseAjax(true);">
<form method="get" action="getMessage.jsp" >
input message:<input id="message" type="text"/>
<input type="button" value="sendMessage" onclick="sendMessage()"/>
<div id="list"></div>
</form>
</body>
</html>

6.把web项目部署到服务器上，启动服务器。分别打开多个浏览器。最后可以看到，在a浏览器发消息，b浏览器会自动出现a浏览器发出的消息。也就是消息的实时传递。

（编辑：李大同）

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