Ajax小程序（ajaxTest.jsp,AjaxServer.java）

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文件放置位置明细：

*************ajaxTest.jsp************************************

<%@ page contentType="text/html;charset=GBK"%>
<html>
<head>
<title>ajaxTest</title>
<script language="JavaScript">
var xmlhttp;
function submit() {
if (window.XMLHttpRequest) {
//IE7,IE8,FireFox,Mozilla,Opera,Safari都会创建成功；
//alert("IE7,IE8,FireFox,Mozilla,Opera,Safari");
xmlhttp = new XMLHttpRequest();
//如果服务器返回来的头不是text/html则忽略
if (xmlhttp.overrideMimeType) {
xmlhttp.overrideMimeType("text/xml");
}
}
else if (window.ActiveXObject){
//如果条件成立，则是IE6,IE5.5,IE5
//alert("IE6,IE5.5,IE5");
var activexName=["MSXML2.XMLHTTP.6.0","MSXML2.XMLHTTP.5.0",
"MSXML2.XMLHTTP.4.0","MSXML2.XMLHTTP.3.0","MSXML2.XMLHTTP","Miscrosoft.XMLHTTP",];
for(var i=0;i<activexName.length;i++)
{
try{
xmlhttp=new ActiveXObject(activexName[i]);
break;
}
catch(e){}
}
}
else if(xmlhttp==null||xmlhttp==undefind){
//alert("当前浏览器不支持XMLHttpRequest对象，请更换浏览器！");
}
//alert(xmlhttp);
//注册回调方法
xmlhttp.onreadystatechange=callback;//注意写的是方法名，不需要加（）
var username=document.getElementById("UserName").value;
//,设置与服务器端交互参数，用GET方法，true表示异步交互。
xmlhttp.open("GET","/AjaxServer?name="+username,true);
xmlhttp.send(null);
}
function callback()
//判断服务器的交互是否完成，判断服务器是否正确返回数据
{
if(xmlhttp.readyState==4)
{
//表示和服务器端交互已完成
if(xmlhttp.status==200)
//表示服务器的相应代码是200，正确返回了数据
//纯文本数据接收方法
{
var message=xmlhttp.responseText;
//xml对应的dom对象接收方法
//使用前提是服务器端需要设置contentType为text/xml
//var domXml=xmlhttp.responseText;

//向div标签中添加纯文本内容的方法
var div=document.getElementById("message");
div.innerHTML=message;
}
}
}
</script>
</head>
<body>
<input type="text" id="UserName"></input>
<input type="button" value="校验用户名" onclick="submit()"></input>
<div id="message"></div>
</body>

</html>

*************AjaxServer.java***********************************************************

package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;

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

public class AjaxServer extends HttpServlet {

/**
* Constructor of the object.
*/
public AjaxServer() {
super();
}

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}

/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try{
// request.setCharacterEncoding("UTF-8");
// response.setContentType("text/html;charset=gb18030");

response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();

Integer inte = (Integer) request.getSession().getAttribute("total");
int temp = 0;
if (inte == null) {
temp = 1;
} else {
temp = inte.intValue() + 1;
}
request.getSession().setAttribute("total",temp);

//1.取参数
String old = request.getParameter("name");
//String name = new String(old.getBytes("iso8859-1"),"UTF-8");
String name = URLDecoder.decode(old,"UTF-8");
//2.检查参数是否有问题
if(old == null || old.length() == 0){
out.println("用户名不能为空");
} else{
// String name = URLDecoder.decode(old,"UTF-8");
// byte[] by = old.getBytes("ISO8859-1");
// String name = new String(by,"utf-8");
// String name = URLDecoder.decode(old,"utf-8");
//3.校验操作
// String name = old;
if(name.equals("robin")){
//4。和传统应用不同之处。这一步需要将用户感兴趣的数据返回给页面段，而不是将一个新的页面发送给用户
//写法没有变化，本质发生了改变
out.println("用户名[" + name + "]已经存在，请使用其他用户名, " + temp);
} else{
out.println("用户名[" + name + "]尚未存在，可以使用该用户名注册, " + temp);
}
}
} catch(Exception e){
e.printStackTrace();
}
}

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}

}

**********web.xml****************************************************************

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/j2ee"
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>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ClassicServer</servlet-name>
<servlet-class>servlet.ClassicServer</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>AjaxServer</servlet-name>
<servlet-class>servlet.AjaxServer</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ClassicServer</servlet-name>
<url-pattern>/servlet/ClassicServer</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>AjaxServer</servlet-name>
<url-pattern>/servlet/AjaxServer</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

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