1.usercheck.html

href="../lib/ligerUI/skins/Aqua/css/usertext.css" rel="stylesheet"

type="text/css" />

填写用户名

/>

id="verifyButton"/>

2.usertext.css

.userClass {

border: 1px solid red ;

background-image:

url(../../../../../images/star.gif);

background-repeat: repeat-x;

background-position: bottom;

}

3.useropera.js

$(document).ready(function(){

$("#verifyButton").click(function(){

var userName=$("#text1").val();

if(userName==""){

alert("用户名不能为空");

}else{

//将用户名传到servlet中

$.get("http://127.0.0.1:8080/ServletDemo/Demo?user="+ encodeURI(encodeURI(userName)),null,function(response){

$("#result").html(response);

});

}

});

$("#text1").keyup(function(){

var value =

$(this).val();

if(value==""){

$(this).addClass("userClass");

}else {

$(this).removeClass("userClass");

}

});

});

4.Demo

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class Demo extends HttpServlet {

public

Demo() {

}

public void

doGet(HttpServletRequest req,HttpServletResponse res){

try{

res.setHeader("Cache-Control", "no-cache");

res.setContentType("text/text;charset=UTF-8");

req.setCharacterEncoding("UTF-8");

String

u=req.getParameter("user");; //PrintWriter pw=res.getWriter(); FileReader fr=new

FileReader("E:\\jquery\\JQuery\\file\\userName.txt");

BufferedReader br=new

BufferedReader(fr);

String line;

boolean flag=false;

while((line

=br.readLine())!=null){

if(line.equalsIgnoreCase(u)){

PrintWriter out = res.getWriter();

out.write("此用户名已经被注册!");

out.flush();

out.close(); flag=true; }

}

br.close();

if(!flag){