ajax real-time verification whether username exists-javaTutorial-php.cn

ajax real-time verification whether username exists

巴扎黑

Release： 2016-12-03 11:53:06

Original

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1. jsp page

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>ajax验证用户名是否可用</title>
<script type="text/javascript">
var xmlHttp = null;
function checkUserName(){
var userName = document.getElementById("userName").value;
if(window.ActiveXObject){
// 申明XMLHttpRequest对象，针对较低版本的IE（5，6，7）
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); 
}else{
// 申明XMLHttpRequest对象，针对较高版本的IE（8+，以及主流浏览器）
xmlHttp = new XMLHttpRequest();
}
// get方式提交，带参数，异步
xmlHttp.open("get","ajax?userName="+userName,true);
// 调用回调函数
xmlHttp.onreadystatechange = callback;
xmlHttp.send();
}
// 回调函数
function callback(){
if(xmlHttp.readyState == 4){
            if(xmlHttp.status == 200){
                // xmlHttp.responseText，获取后台返回信息
                document.getElementById("label").innerHTML = xmlHttp.responseText;
            }else{
                alert("AJAX服务器返回错误！");
            }    
        }
}
function checkForm(){
if(document.getElementById("label").innerHTML != "<font color=\"green\">用户名可用</font>"){
             document.getElementById("userName").focus();
             return false;
         }
return true;
}
</script>
</head>
<body>
<form action="login" method="post" onsubmit="return checkForm()">
用户名：<input type="text" onblur="checkUserName()" id="userName" name="userName">
<label id="label"></label><br>
密码：<input type="password"><br>
<input type="submit">
</form>
</body>
</html>

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2. web.xml

Java code

<!-- ajax获取信息 -->  
<servlet>  
  <servlet-name>AjaxServlet</servlet-name>  
  <servlet-class>com.servlet.AjaxServlet</servlet-class>  
</servlet>  
<servlet-mapping>  
  <servlet-name>AjaxServlet</servlet-name>  
  <url-pattern>/ajax</url-pattern>  
</servlet-mapping>

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3. servlet

Java code

package com.servlet;  
  
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 AjaxServlet extends HttpServlet {  
    private static final long serialVersionUID = 1L;  
    protected void doGet(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
        this.doPost(request, response);  
    }  
  
    protected void doPost(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
        request.setCharacterEncoding("UTF-8");  
        response.setContentType("text/html;charset=UTF-8");  
        PrintWriter out = response.getWriter();  
          
        String userName = request.getParameter("userName");  
          
        if(userName.equals("admin")){  
            out.print("<font color=&#39;red&#39;>用户名已经存在</font>");  
        }  
        else if (userName.length() == 0) {  
            out.print("<font color=&#39;red&#39;>用户不能为空</font>");  
        }  
        else if (userName.indexOf(" ") > 0) {  
            out.print("<font color=&#39;red&#39;>用户不能含有空格</font>");  
        }  
        else if (userName.length() > 10 || userName.length() < 4) {  
            out.print("<font color=&#39;red&#39;>用户长度在4-10之间</font>");  
        }  
        else {  
            out.print("<font color=&#39;green&#39;>用户名可用</font>");  
        }  
        out.flush();  
        out.close();  
    }  
}

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