简单验证码实现

1、first.jsp页面代码

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>    
<html> 
    <head> 
        <title>验证码</title> 
        <meta http-equiv='content-type' content='text/html;charset=utf-8'/>
        <link href="${pageContext.request.contextPath}/statics/localcss/first.css" rel="stylesheet"> 
        <script type='text/javascript' src='jquery-1.7.2.js'></script> 
           <script  type="text/javascript" 
            src="${pageContext.request.contextPath}/statics/localjs/first.js"></script>
    
    </head> 
    <body onload='createCode()'> 
    <div> 
            用户名：<input type="text" name="loginCode" placeholder="请输入用户名"/><br/>
         密   码：<input type="password" name="password" placeholder="请输入密码"/><br/>
                      验证码：<input type = "text" id = "input" placeholder="请输入验证码"/>   
            <input type="button" id="code" onclick="createCode()" title='点击更换验证码' /> 
            <input type = "button" value = "验证" onclick = "validate()"/> 
        </div>   
    </body> 
</html>

2、添加样式

#code{ 
font-family:Arial,宋体; 
font-style:italic; 
color:green; 
border:0; 
padding:2px 3px; 
letter-spacing:3px; 
font-weight:bolder; 
width:60px;
background-image: url("${pageContext.request.contextPath }/statics/img/761658199044341639.jpg")   //背景图片可以自己设置
}

3、first.js

var code; //在全局定义验证码   

function createCode() {
    code = "";
    var codeLength = 4;//验证码的长度   
    var checkCode = document.getElementById("code");
    var random = new Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 'A', 'B', 'C', 'D',
            'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q',
            'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z');//随机数   
    for ( var i = 0; i < codeLength; i++) {//循环操作   
        var index = Math.floor(Math.random() * 36);//取得随机数的索引（0~35）   
        code += random[index];//根据索引取得随机数加到code上   
    }
    checkCode.value = code;//把code值赋给验证码   
}
//校验验证码   
function validate() {
    var inputCode = document.getElementById("input").value.toUpperCase(); //取得输入的验证码并转化为大写         
    if (inputCode.length <= 0) { //若输入的验证码长度为0   
        alert("请输入验证码！"); //则弹出请输入验证码   
    } else if (inputCode != code) { //若输入的验证码与产生的验证码不一致时   
        alert("验证码输入错误！@_@"); //则弹出验证码输入错误   
        createCode();//刷新验证码   
        document.getElementById("input").value = "";//清空文本框   
    } else { //输入正确时   
        alert("合格！^-^");
    }
}

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