javaweb开发中异步ajax请求之DWR框架详解（通过直接访问java类实现异步请求处理）

   DWR是一个开源的服务器端ajax框架，js通过直接调用普通java类中的方法实现服务器端数据处理。原理：框架根据配置在加载页面的时候自动生成ajax代码供前端调用。

        该框架只需一个jar包 csdn有下载：dwr(免费)

   web.xml

    

<listener><!--配置监听器 默认启动时加载dwr.xml（后面有配置） 路径和web.xml一致-->
    <listener-class>org.directwebremoting.servlet.DwrListener</listener-class>
  </listener>
  <servlet><!-- 配置servlet和映射路径 下面有相关参数 比如fileUploadMaxBytes是允许文件上传的大小-->
    <servlet-name>dwr-invoker</servlet-name>
    <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
    <init-param>
      <param-name>fileUploadMaxBytes</param-name>
      <param-value>25000000000000</param-value>
    </init-param>
    <init-param>
      <param-name>debug</param-name>
      <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>accessLogLevel</param-name>
      <param-value>runtimeexception</param-value>
    </init-param>
    <init-param>
      <param-name>activeReverseAjaxEnabled</param-name>
      <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>initApplicationScopeCreatorsAtStartup</param-name>
      <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>jsonRpcEnabled</param-name>
      <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>jsonpEnabled</param-name>
      <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>preferDataUrlSchema</param-name>
      <param-value>false</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dwr-invoker</servlet-name>
    <url-pattern>/dwr/*</url-pattern>
  </servlet-mapping>

   dwr.xml（与web.xml在同一目录）

   

<?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="mytest"><!-普通java类-->
      <param name="class" value="org.ITschool.dwr.utilcontroller.mytest"/>
    </create>
    <!-- this is a bad idea for live, but can be useful in testing -->
    <!-- <create creator="spring" javascript="User_Service">
     <param name="BeanName" value="User_Service" />
     </create>-->
      <create javascript="User_Service" creator="spring"><!--使用Spring配置中的bean-->
     <param name="beanName" value="User_Service"/>
      </create>
    <create creator="new" javascript="Uploadprocess">
      <param name="class" value="org.ITschool.dwr.utilcontroller.Uploadprocess"/>
    </create>
     <create creator="new" javascript="uploadFile">
      <param name="class" value="org.ITschool.dwr.utilcontroller.uploadFile"/>
    </create>
    
    <convert converter="exception" match="java.lang.Exception"/>
    <convert converter="bean" match="java.lang.StackTraceElement"/>
   
  </allow>

</dwr>

   现在看下上面mytest.java文件的代码(以我项目中的代码为例)

package org.ITschool.dwr.utilcontroller;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.directwebremoting.WebContext;
import org.directwebremoting.WebContextFactory;

import net.sf.json.JSON;
import net.sf.json.JSONObject;

public class mytest {
	
  public JSON getInfo(String info1){
	    JSONObject json=new JSONObject();
	    json.put("name", "XXXX");
	    json.put("name1", info1);
	 
	  return json;
  }}

  最后看下前端调用了(引入必要的js)

<script type='text/javascript' src='dwr/engine.js'></script><!--必须引入的 js代码由框架自动生成-->
<script type='text/javascript' src='dwr/util.js'></script><!--必须引入的  js代码由框架自动生成-->
<script type='text/javascript' src='dwr/interface/mytest.js'></script><!---dwr.xml中配置的mytest java类->

   再看调用

<script type='text/javascript'>
 mytest.getInfo(“方法参数”,function(data){//前一个是方法参数 后面是回调函数

  alert(data.name)

});
</script>

运行结果：弹出 XXXX内容的提示框架。