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kaptcha是一个简单好用的验证码生成工具，有了它，你可以生成各种样式的验证码，因为它是可配置的。kaptcha工作的原理是调用 com.google.code.kaptcha.servlet.KaptchaServlet，生成一个图片。同时将生成的验证码字符串放到 HttpSession中。
使用kaptcha可以方便的配置：
第一步：添加kaptcha依赖的jar包
第二步：配置web.xml 文件
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <!-- kaptcha验证码配置 --> <servlet> <!-- 生成图片的Servlet --> <servlet-name>Kaptcha</servlet-name> <servlet-class> com.google.code.kaptcha.servlet.KaptchaServlet </servlet-class> <!-- 是否有边框--> <init-param> <param-name>kaptcha.border</param-name> <param-value>no</param-value> </init-param> <!-- 字体颜色 --> <init-param> <param-name>kaptcha.textproducer.font.color</param-name> <param-value>red</param-value> </init-param> <!-- 图片宽度 --> <init-param> <param-name>kaptcha.image.width</param-name> <param-value>135</param-value> </init-param> <!-- 使用哪些字符生成验证码 --> <init-param> <param-name>kaptcha.textproducer.char.string</param-name> <param-value>ACDEFHKPRSTWX345679</param-value> </init-param> <!-- 图片高度 --> <init-param> <param-name>kaptcha.image.height</param-name> <param-value>50</param-value> </init-param> <!-- 字体大小 --> <init-param> <param-name>kaptcha.textproducer.font.size</param-name> <param-value>43</param-value> </init-param> <!-- 干扰线的颜色 --> <init-param> <param-name>kaptcha.noise.color</param-name> <param-value>black</param-value> </init-param> <!-- 字符个数 --> <init-param> <param-name>kaptcha.textproducer.char.length</param-name> <param-value>4</param-value> </init-param> <!-- 使用哪些字体 --> <init-param> <param-name>kaptcha.textproducer.font.names</param-name> <param-value>Arial</param-value> </init-param> </servlet> <!-- 映射的url --> <servlet-mapping> <servlet-name>Kaptcha</servlet-name> <url-pattern>/Kaptcha.jpg</url-pattern> </servlet-mapping> <!-- 检查验证码是否输入正确 --> <servlet> <servlet-name>VerifyServlet</servlet-name> <servlet-class> me.gacl.web.controller.VerifyServlet </servlet-class> </servlet> <servlet-mapping> <servlet-name>VerifyServlet</servlet-name> <url-pattern>/servlet/VerifyServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
第三步：添加控制器
package me.gacl.web.controller; 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 VerifyServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charaset=utf-8"); response.setHeader("pragma", "no-cache"); response.setHeader("cache-control", "no-cache"); PrintWriter out = null; try { // 响应数据 String resultData; // 获取传过来的验证码 String verifyCode = request.getParameter("verifyCode"); System.out.println("verifyCode----" + verifyCode); if (verifyCode == "") { resultData = "N"; } else { // 获取kaptcha生成存放在session中的验证码 String kaptchaValue = (String) request .getSession() .getAttribute( com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY); // 比较输入的验证码和实际生成的验证码是否相同 if (kaptchaValue == null || kaptchaValue == "" || !verifyCode.equalsIgnoreCase(kaptchaValue)) { resultData = "N"; } else { resultData = "Y"; } } out = response.getWriter(); out.write(resultData); out.flush(); } catch (Exception e) { e.printStackTrace(); } finally { if (out != null) { out.close(); } } } }
第四步：添加页面index.jsp .
<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML>
<html>
<head>
<title>显示KaptchaServlet生成的验证码</title>
<script type="text/javascript"
src="${pageContext.request.contextPath}/js/jquery-1.9.1.min.js"></script>
<script type="text/javascript">
//点击切换验证码
function changeVerifyCode(){
$("#yzmImg").attr("src","Kaptcha.jpg?"+Math.floor(Math.random()*100));
}
//提交
function doSubmit() {
var verifyCodeValue = $("#verifyCode").val();
if(verifyCodeValue.replace(/\s/g,"") == "") {
alert("请输入验证码");
}else {
//提交前先异步检查验证码是否输入正确
var verifyUrl = "${pageContext.request.contextPath}/servlet/VerifyServlet?verifyCode="+verifyCodeValue;
$.ajax({
type:"GET",
url:verifyUrl,
success:function(returnData){
if(returnData!="Y") {
alert("请输入正确的验证码！");
}else {
//验证码正确，进行提交操作
alert("验证码输入正确，提交表单");
}
},
error:function(e){
alert(e);
}
});
}
}
</script>
</head>
<body>
<form>
<table>
<tr>
<td>
请输入验证码：
</td>
<td>
<input type="text" name="verifyCode" id="verifyCode">
<img src="Kaptcha.jpg" onclick="changeVerifyCode()" id="yzmImg"
style="cursor: pointer;">
<a href="javascript:void(0)" onclick="changeVerifyCode()">看不清，换一张</a>
</td>
</tr>
<tr>
<td>
</td>
<td>
<input type="button" value="提交" onclick="doSubmit()">
</td>
</tr>
</table>
</form>
</body>
</html>
源码下载：http://yunpan.cn/cwrSZdFaJv2sS 访问密码 888e
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原文地址：http://www.cnblogs.com/liuhongfeng/p/4538162.html
