DWR的使用

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DWR包括两个主要部分:

1.一个Java Servlet处理请求和服务器上运行将响应发送回浏览器。

2.JavaScript,可以运行在浏览器发送请求动态地更新网页。

DWR是通过基于Java的动态生成的Javascript 类。 Ajax代码做一些魔法使的感觉发生在浏览器上执行,但事实上服务器执行的代码和DWR编组数据转发。

这个方法从Java远程函数的JavaScript给DWR 用户感觉很像传统的RPC机制(好处,它运行在网络上,不需要浏览器插件)。

1.首先配置web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app version="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/javaeehttp://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">    <welcome-file-list>        <welcome-file>index.jsp</welcome-file>    </welcome-file-list>    <servlet>        <display-name>DWR Servlet</display-name>        <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></web-app>

2.在web.xml的同级目录下也就是web-inf下创建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>    <allow>        <create creator="new" javascript="JDate">            <param name="class" value="java.util.Date"/>        </create>        <create creator="new" javascript="DwrDemo">            <param name="class" value="com.wem.Dome.DwrDemo"/>        </create>    </allow></dwr>

3.在项目lib中导入如下包

1.dwr.jar
2.commons-logging-1.0.4.jar

4.创建一个java类，如在dwr.xml中写的DwrDemo.java

package com.wem.Dome;public class DwrDemo {    public String getHello(String name) {        System.out.println("我进入了getHello方法");        return name + " 你好！";    }}

5.创建jsp文件MyDwr.jsp

<%--  Created by IntelliJ IDEA.  User: Administrator  Date: 2016-07-26  Time: 9:56  To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></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/DwrDemo.js'></script><script>    function test(){        DwrDemo.getHello("java", {            callback:function(str) {                alert(str);            }        });    }</script><body>     <input type="button" onclick="test()" value="点击"/></body></html>

点击显示如下

后台打印情况

二:服务器推送数据到前台，调用相关js方法

DwrDemo.java修改为

package com.wem.Dome;import org.directwebremoting.Browser;import org.directwebremoting.ScriptBuffer;import org.directwebremoting.ScriptSession;import java.util.Collection;public class DwrDemo {    public String getHello(String name) {        System.out.println("我进入了getHello方法");        Runnable run = new Runnable(){            private ScriptBuffer script = new ScriptBuffer();            public void run() {                //设置要调用的 js及参数                script.appendCall("load","很高兴认识你");                //得到所有ScriptSession                Collection<ScriptSession> sessions = Browser.getTargetSessions();                //遍历每一个ScriptSession                for (ScriptSession scriptSession : sessions){                    scriptSession.addScript(script);                }            }        };        //执行推送        Browser.withAllSessions(run);        return null;    }}

2.MyDwr.jsp修改为

<%--  Created by IntelliJ IDEA.  User: Administrator  Date: 2016-07-26  Time: 9:56  To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></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/DwrDemo.js'></script><script>    function test(){        DwrDemo.getHello("java", {            callback:function(str) {                alert(str);            }        });    }    //这个方法用来启动该页面的ReverseAjax功能    dwr.engine.setActiveReverseAjax(true);    //设置在页面关闭时，通知服务端销毁会话    dwr.engine.setNotifyServerOnPageUnload(true);    //这个函数是提供给后台推送的时候 调用的    function load(value){        document.getElementById("pID").innerHTML=value;    }</script><body>     <input type="button" onclick="test()" value="点击"/>    <p id="pID">java你好</p></body></html>

原显示结果

推送后的结果

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