package tt;
import java.io.IOException;
import java.io.
PRintWr
ITer;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
p
ublic class
testA extends HttpServlet {
private
static final long serialVersionUID = -7999241892841130740L;
protected void doGet(HttpServletRequest request,
HttpServletResponse response) t
hrows ServletException, IOException {
request.setCharacterEncoding("utf-8");
String n
ame = request.getParameter("name");
response.setContentTy
PE("text/
XMl; charset=utf-8");
response.setHeader("Cache-Control", "no-cache");
PrintWriter out = response.getWriter();
out.println("<pront>");
if (name.equals("yangjinde")) {
out.println("<content>" + "对不起,'yangjinde'此名已经注册" + "</content>");
} else {
out.println("<content>" + "可以注册哦" + "</content>");
}
out.println("</pront>");
out.close();
}
}
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HT
ML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>
;my JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="e
xpires" content="0">
<meta http-equiv="keywo
rds" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script>
//设一个变量
VAR XMLHttpReq=false;
//创建一个XMLHttpRequest对象
function createXMLHttpRequest(){
if(window.XMLHttpRequest){ //Mozilla
XMLHttpReq=new XMLHttpRequest();
}
else if(window.ActiveXObject){
try{
XMLHttpReq=new ActiveXObject("Msxml2.XMLHTTP");
}catch(e){
try{
XMLHttpReq=new ActiveXObject("Microsoft.XMLHTTP");
}catch(e){}
}
}
}
//发送请求函数
function send(url){
createXMLHttpRequest();
XMLHttpReq.open("GET",url,true);
XMLHttpReq.onreadystatechange=proce; //指定响应的函数
XMLHttpReq.send(null); //发送请求
}
function proce(){
if(XMLHttpReq.readyState
==4){ //对象状态
if(XMLHttpReq.status==200){//信息已成功返回，
开始处理信息
var res=XMLHttpReq.responseXML.
getelementsbytagname("content")[0].
FirstChild.data;
window.alert(res);
document.getElementById("data").innerHTML = res;
document.getElementById("name").value = res;
}else{
window.alert("不好
意思，所请求的页面有异常");
}
}
}
//身份验证
function check(){
var name=document.getElementById("name").value;
if(name==""){
alert("请输入内容哦");
return false;
}
else{
send('lo
gin?name='+name);
}
}
</script>
</head>
<body>
<form action="
LOGin" method="post">
<tr><td>姓名: <input id="name" type="text" name="name"/>
<input type="button" value="点我试试看" onClick="check()"/>
</td>
</tr>
<tr><td><div id="data">等下我会变哦！！</div></td></tr>
</form>
</body>
</html>
3.
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
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/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<servlet-name>login</servlet-name>
<servlet-class>tt.TestA</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>login</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>