wiley

Ajax,它使浏览器可以为用户提供更为自然的浏览体验,对于j2EE WEB开发人员来说,使用DWR框架可以很简单的使用Ajax技术.
本文以一个DWR+SPRING的实例来说明DWR的使用
1、将dwr.jar放到应用的/WEB-INF/lib目录下
2、配置web.xml,增加如下代码:

<!--初始化WebApplicationContext-->
 <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/applicationContext.xml,/WEB-INF/action-servlet.xml</param-value>
 </context-param>
 <listener>
       <listener-class>
             org.springframework.web.context.ContextLoaderListener
       </listener-class>
 </listener>
<!--配置DWR拦截器-->
 <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>

3、增中dwr.xml文件
文件内容：

<?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="spring" javascript="DWRUser">
   <param name="beanName" value="DWRUser"/>
  </create>
 </allow>
</dwr>

creator属性的值可以是new,struts,spring......因为此处是整合spring来做的，所以设置成“spring”，javascript="DWRUser" 表示实例转换成javascript语言后以DWRUser命名，前台页面可以通过代码（<script type='text/javascript' src='../../dwr/interface/DWRUser.js'></script>）来调用。param元素的name属性值可以是class,beanName等，此处用beanName,value得值是定义在applicationContext.xml中某个bean的id值。
4、创建一个实体bean供DWR转换成js

package com.note.dwr;
import com.note.bussies.service.IUserService;
public class User {
 private IUserService ius;
 
 public IUserService getIus() {
  return ius;
 }
 public void setIus(IUserService ius) {
  this.ius = ius;
 }
 public User(){
  
 }
 public boolean isExist(String username) {
      Users user = this.ius.getUserByName(username);
      return (null == user) ? false : true;
 }
}

5、在applicationContext.xml中配置第4步写的bean

......
 <bean id="DWRUser" class="com.note.dwr.User">
  <property name="ius">
   <ref bean="UserService" />
  </property>
 </bean>
......

6、在视图页面中调用
先导入以下文，每个文件的功能这里不再详述

 <script type='text/javascript' src='../../dwr/interface/DWRUser.js'></script>
 <script type='text/javascript' src='../../dwr/engine.js'></script>
 <script type='text/javascript' src='../../dwr/util.js'></script>

因为我的视图文件是放在/view/user/下，所以这里用了../../返回到根
具体调用：

 <script type='text/javascript'>
  function regUserChked(){
   var username=$("username").value;
   DWRUser.isExist(username,showData);//showData回调函数
  }
  function showData(data){
      if(data){
           DWRUtil.setValue("userMsg","该用户名已经被注册，请更换您的用户名！");
      }else{
           DWRUtil.setValue("userMsg","恭喜您，该用户名尚未被注册！");      
      }
  }
 </script>
<input type="text" name="username" value="" onblur="regUserChked()" /><div id="userMsg"></div>