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How to check if username is unique using AJAX

一个新手Original: 2017-09-27 09:35:471690browse

After learning theory, you must use practical operations to consolidate your knowledge.

Write a simple example below to check whether the user name is unique (code directly):

Front-end interface:

<%@ page language="java" contentType="text/html; charset=GB18030"
    pageEncoding="GB18030"%><!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=GB18030"><title>检测用户名是否唯一</title><style type="text/css"><!--#toolTip {    position:absolute;    left:331px;    top:39px;    width:98px;    height:48px;    padding-top:45px;    padding-left:25px;    padding-right:25px;    z-index:1;    display:none;    color:red;    background-image: url(images/tooltip.jpg);}--></style></head><body style="margin: 0px;"><form method="post" action="" name="form1"><table width="509" height="352" border="0" align="center" cellpadding="0" cellspacing="0" background="images/bg.gif">
  <tr>
    <td height="54"> </td>
  </tr>
  <tr>
    <td height="253" valign="top">
    <p style="position:absolute;">


    <table width="100%" height="250" border="0" cellpadding="0" cellspacing="0">
      <tr>
        <td width="18%" height="54" align="right" style="color:#8e6723 "><b>用户名：</b></td>
        <td width="49%"><input name="username" type="text" id="username" size="32"></td>
        <td width="33%"><img  src="images/checkBt.jpg"    style="max-width:90%"  style="max-width:90%" style="cursor:hand;" onClick="checkUser(form1.username);" alt="How to check if username is unique using AJAX" ></td>
      </tr>
      <tr>
        <td height="51" align="right" style="color:#8e6723 "><b>密码：</b></td>
        <td><input name="pwd1" type="password" id="pwd1" size="35"></td>
        <td rowspan="2">     <p id="toolTip"></p></td>
      </tr>
      <tr>
        <td height="56" align="right" style="color:#8e6723 "><b>确认密码：</b></td>
        <td><input name="pwd2" type="password" id="pwd2" size="35"></td>
        </tr>
      <tr>
        <td height="55" align="right" style="color:#8e6723 "><b>E-mail：</b></td>
        <td colspan="2"><input name="email" type="text" id="email" size="45"></td>
      </tr>
      <tr>
        <td> </td>
        <td colspan="2"><input type="image" name="imageField" src="images/registerBt.jpg"></td>
      </tr>
    </table>
    </p>
    </td>
  </tr>
  <tr>
    <td> </td>
  </tr></table></form></body></html>

AJAX file:

<script language="javascript">function createRequest(url) {
    http_request = false;    
    if (window.XMLHttpRequest) {                                   // 非IE浏览器
        http_request = new XMLHttpRequest();                          //创建XMLHttpRequest对象
    } else if (window.ActiveXObject) {                             // IE浏览器
        try {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");    //创建XMLHttpRequest对象
        } catch (e) {            
        try {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");  //创建XMLHttpRequest对象
           } catch (e) {}
        }
    }    if (!http_request) {
        alert("不能创建XMLHttpRequest对象实例！");        
        return false;
    }
    http_request.onreadystatechange = getResult;                       //调用返回结果处理函数
    http_request.open(&#39;GET&#39;, url, true);                               //创建与服务器的连接
    http_request.send(null);                                       //向服务器发送请求}function getResult() {
    if (http_request.readyState == 4) {             // 判断请求状态
        if (http_request.status == 200) {           // 请求成功，开始处理返回结果
            document.getElementById("toolTip").innerHTML=http_request.responseText; //设置提示内容
            document.getElementById("toolTip").style.display="block";   //显示提示框
        } else {                            // 请求页面有错误
            alert("您所请求的页面有错误！");
        }
    }
}function checkUser(userName){
    if(userName.value==""){
        alert("请输入用户名！");userName.focus();return;
    }else{
        createRequest(&#39;checkUser.jsp?user=&#39;+userName.value);
    }
}</script>

jsp file:

This example does not connect to the database, but simply uses an array to simply represent registered users.

<%@ page language="java" import="java.util.*" pageEncoding="GB18030" %>
<%
    String[] userList={"明日科技","mr","mrsoft","wgh"};         //创建一个一维数组
    String user=new String(request.getParameter("user").getBytes("ISO-8859-1"),"GB18030");  //获取用户名
    Arrays.sort(userList);                                  //对数组排序 
    int result=Arrays.binarySearch(userList,user);              //搜索数组
    if(result>-1){        
    out.println("很抱歉，该用户名已经被注册！");          //输出检测结果
    }else{        
    out.println("恭喜您，该用户名没有被注册！");          //输出检测结果
    }
%>

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How to check if username is unique using AJAX

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