JAVA中的AJAX技术(3)_H5之家 - 中国HTML5教程资源分享第一站

首先，我们仍然是对Struts应用来做配置，仍然是在struts-config,xml文件里做配置，如下：
<action type="com.ajax.CheckAction"
     scope="request" path="/ajax/check">
       <forward path="/check.jsp"/>
</action>

    跟普通的Struts应用的配置一样，只是没有ActionForm的配置。
    下面是Action类：
package com.ajax;

import java.io.PrintWriter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.DynaActionForm;

/**
* @author Administrator
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class CheckAction extends Action
{
  public final ActionForward execute(ActionMapping mapping, ActionForm form,
             HttpServletRequest request,
             HttpServletResponse response)
   throws Exception
   {
    System.out.println("haha...............................");
    String username= request.getParameter("username");
    System.out.println(username);
    String retn;
    if("educhina".equals(username)) retn = "Can't use the same name with the old use,pls select a difference...";
    else retn = "congraducation!you can use this name....";
    PrintWriter out=response.getWriter();
             out.write(retn);
             out.close();
    return mapping.findForward("success");
   }
  public static void main(String[] args)
  {
  }
}

    我们可以看到里面的逻辑跟上例中Servlet里的逻辑一样。最后，我们来看看JSP:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Check.html</title>

<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">



</head>
<script type="text/javascript">
  var http_request = false;
function send_request(url) {//初始化、指定处理函数、发送请求的函数
   http_request = false;
   //开始初始化XMLHttpRequest对象
   if(window.XMLHttpRequest) { //Mozilla 浏览器
    http_request = new XMLHttpRequest();
    if (http_request.overrideMimeType) {//设置MiME类别
     http_request.overrideMimeType('text/xml');
    }
   }
   else if (window.ActiveXObject) { // IE浏览器
    try {
     http_request = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (e) {
     try {
      http_request = new ActiveXObject("Microsoft.XMLHTTP");
     } catch (e) {}
    }
   }
   if (!http_request) { // 异常，创建对象实例失败
    window.alert("不能创建XMLHttpRequest对象实例.");
    return false;
   }
   http_request.onreadystatechange = processRequest;
   // 确定发送请求的方式和URL以及是否同步执行下段代码
   http_request.open("GET", url, true);
   http_request.send(null);
}
// 处理返回信息的函数
     function processRequest() {
         if (http_request.readyState == 4) { // 判断对象状态
             if (http_request.status == 200) { // 信息已经成功返回，开始处理信息
                 alert(http_request.responseText);
             } else { //页面不正常
                 alert("您所请求的页面有异常。");
             }
         }
     }
function userCheck() {
   var f = document.forms[0];
   var username = f.username.value;
   if(username=="") {
    window.alert("The user name can not be null!");
    f.username.focus();
    return false;
   }
   else {
    send_request('ajax/check.do?username='+username);
   }
}

</script>
<body>
  <form action="" method="post">
User Name:<input type="text" value=""> 
<input type="button" value="check">
<input type="submit" value="submit">
</form>
</body>
</html>

    我们可以看到，JSP基本是一样的，除了要发送的url：ajax/check.do?username='+username。