用Ajax可以在不刷新整个页面的情况下与服务器动态连接，这里做了个简单小的例子用到了jsp ajax servlet
先创建一个web项目 Login_demo
1.首先写个servlet，用户输入的登陆信息被提交到这里servlet中，对用户输入的信息判断
Loginservlet.java
在web.xml中的配置如下
<servlet>
<servlet-name>Loginservlet</servlet-name>
<servlet-class>com.login.Loginservlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Loginservlet</servlet-name>
<url-pattern>/servlet/Loginservlet</url-pattern>
</servlet-mapping>
——————————————————————
package com.login;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Loginservlet extends HttpServlet {
public Loginservlet() {
super();
}
public void destroy() {
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
response.setCharacterEncoding("gbk");
PrintWriter out = response.getWriter();
String name = request.getParameter("name");
String pass = request.getParameter("pass");
//这里为了方便就硬性的给了两个值，当然你可以从数据库中得到
if(name.equals("luofang")&&pass.equals("123")){
out.print("suc");//用户名密码正确就返回字符suc
} else {
out.print("fail");//失败就返回字符fail
}
out.flush();
out.close();
}
public void init() throws ServletException {
// Put your code here
}
}
2.现在来写jsp页面主要就是写javascript
<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>用户登陆</title>
</head><script language="javascript">
var xmlhttp;
var name;
//创建XMLHttprequest
function createXMLHttpRequest(){
if(window.ActiveXObject){
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}else{
xmlhttp = new XMLHttpRequest();
}
}
function startRequest(){
name=document.getElementById("name").value;
var pass=document.getElementById("pass").value;
if(name==""){
alert("用户名为空！");
return false;
}
if(pass==""){
alert("密码为空！");
return false;
}
var url="http://localhost:8080/Login_demo/servlet/Loginservlet?name="+name+"&pass="+pass;
createXMLHttpRequest();
//设置状态改变时所调用的函数
xmlhttp.onreadystatechange = stateChange ;
//设置对服务器的调用
xmlhttp.open("GET",url,true);
//发送请求
xmlhttp.send(null);
}
function stateChange(){
if(xmlhttp.readyState==4){
if(xmlhttp.status==200){
//做你想在页面上做的事情
//document.getElementById("mess").innerHTML=xmlhttp.responseText;
//如果用户名密码正确返回suc，错误返回fail
if(xmlhttp.responseText=="suc"){
// document.getElementById('login').style.display='none';
//document.getElementById("mess").innerHTML=name+"：您好！";
document.getElementById('login').innerHTML=name+":您好!";
}
else{
alert("登陆失败！用户名或密码不正确！");
document.getElementById("pass").value="";
document.getElementById("name").focus();
}
}
}
}
</script>
<body>
<div style="width:570">
<div style="float:left" id="login">
名字：<input type="text" maxlength="10" size="10" name="name" id="name">
密码：<input type="password" maxlength="10" size="10" name="pass" id="pass">
<input type="submit" value="登陆" onclick="startRequest();return false;">
</div>
<div style="float:right" id="mess">
<div>
</div>
</body>
</html>
这样就ok了
