dwr学习札记（一）

2012-11-22

dwr学习笔记（一）像以前学习编程语言一样，学习dwr第一步，也不免先写一个类似于hello，world这样的小代码，在

dwr学习笔记（一）
像以前学习编程语言一样，学习dwr第一步，也不免先写一个类似于hello，world这样的小代码，在这里闲话暂且按下，我们来看具体代码。

具体代码如下：

  index.jsp  <%@ 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>    <title>DWR - Test Home</title>    <script type='text/javascript' src='dwr/interface/Demo.js'></script>    <script type='text/javascript' src='dwr/engine.js'></script>    <script type='text/javascript' src='dwr/util.js'></script>    <script>      function load()      {        JavaDate.getYear(loadCallBack);      }      function loadCallBack(data)      {          alert(data+1900+'年');      }      function hello()      {          var name = document.getElementById("name").value;          Demo.sayHello(name,callBack);      }      function callBack(data)      {          dwr.util.setValue("result", data);      }    </script>  </head>  <body>      <input type="text" name="name" id="name"/>      <input type="button" onclick="hello();" name="button" value="button">      <span id="result" style="background: #eeffdd; padding: 10px"></span>     </body>  </html>

Demo.java:

 package com.wise.ajax;  public class Demo {     public String sayHello(String name){          String str = "hello,"+name;          return str;      }  }

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/javaee    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">    <servlet>        <servlet-name>dwr-invoker</servlet-name>        <servlet-class>uk.ltd.getahead.dwr.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>    <welcome-file-list>        <welcome-file>index.jsp</welcome-file>    </welcome-file-list></web-app>

dwr.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 1.0//EN" "http://www.getahead.ltd.uk/dwr/dwr10.dtd"><dwr>  <allow>    <create creator="new" javascript="JavaDate">      <param name="class" value="java.util.Date"/>    </create>    <create creator="new" javascript="Demo">      <param name="class" value="com.wise.ajax.Demo"/>    </create>  </allow></dwr>

类和配置文件都不难理解，另外dwr.util.setValue("result", data);一看就知道是<script type='text/javascript' src='dwr/util.js'></script> 中赋值的方法，sayHello(name,callBack)也容易理解，name是传入Demo.sayHello的参数，callBack是回调方法， getYear(loadCallBack)中getYear是不需要参数的，这里只需要指定回调方法即可。关键在于回调方法 callBack(data)中这个data，看了半天没看明白，后来上百度百科一查，才知道这个data是用于接收方法的返回值，也就是接收 Demo.sayHello这个方法的返回值。
另外既然dwr.util.setValue("result", data)可以赋值，当然dwr.util.getValue("result")就可以取得result的值咯，相当于document.getElementById("name").value;

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dwr学习札记（一）