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基于HTML，以GET方式，检查注册用户名是否在数据库中已存在

2017-02-03 10:02 435 查看

08_register.jsp

<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>基于HTML，以GET或POST方式，检查注册用户名是否在数据库中已存在</title>
</head>
<body>

<form>
用户名[GET]：<input id="usernameID" type="text" name="username" maxlength="4"/>
光标移出后，立即检查结果
</form>
<hr/>
<span id="resID"></span>

<script type="text/javascript">
//创建AJAX异步对象，即XMLHttpRequest
function createAJAX(){
var ajax = null;
try{
ajax = new ActiveXObject("microsoft.xmlhttp");
}catch(e1){
try{
ajax = new XMLHttpRequest();
}catch(e2){
alert("你的浏览器不支持ajax，请更换浏览器");
}
}
return ajax;
}
</script>

<script type="text/javascript">
//定位文本框，同时提供焦点失去事件
document.getElementById("usernameID").onblur = function(){
//获取文本框中输入的值
var username = this.value;
//如果用户没有填内容
if(username.length == 0){
//提示
document.getElementById("resID").innerHTML = "用户名必填";
}else{
//对汉字进行UTF-8(U8)的编码
username = encodeURI(username);
//NO1)
var ajax = createAJAX();
//NO2)
var method = "GET";
var url = "${pageContext.request.contextPath}/UserServlet?time="+new Date().getTime()+"&username=" + username;
ajax.open(method,url);
//NO3)
ajax.send(null);

//--------------------------------------------------------等待

//NO4)
ajax.onreadystatechange = function(){
if(ajax.readyState == 4){
if(ajax.status == 200){
//NO5)
var tip = ajax.responseText;
//NO6)
document.getElementById("resID").innerHTML = tip;
}
}
}
}
}
</script>
</body>
</html>

UserServlet.java

package cn.itcast.javaee.js.user;

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;

/**
* 基于HTML，以GET或POST方式，检查注册用户名是否在数据库中已存在
* @author AdminTC
*/
public class UserServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
String username = request.getParameter("username");
byte[] buf = username.getBytes("ISO8859-1");
username = new String(buf,"UTF-8");
System.out.println("username=" + username);
String tip = "<font color='green'>可以注册</font>";
if("杰克".equals(username)){
tip = "<font color='red'>该用户已存在</font>";
}
response.setContentType("text/html;charset=UTF-8");
PrintWriter pw = response.getWriter();
pw.write(tip);
pw.flush();
pw.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
String username = request.getParameter("username");
System.out.println("username=" + username);

String tip = "images/MsgSent.gif";
if("杰克".equals(username)){
tip = "images/MsgError.gif";
}
response.setContentType("text/html;charset=UTF-8");
PrintWriter pw = response.getWriter();
pw.write(tip);
pw.flush();
pw.close();
}
}

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