kaptcha是一个简单好用的验证码生成工具，通过配置，可以自己定义验证码大小、颜色、显示的字符等等。
1、下载kaptcha。
http://code.google.com/p/kaptcha/downloads/list
2、新建一个Web项目，并将下载压缩包中的kaptcha-2.3.2.jar放在项目的WEB-INF/lib目录下。
3、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"> <display-name></display-name> <!-- 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> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
4、显示验证码的页面index.jsp
<%@ 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>验证码</title> <script type="text/javascript"> //点击切换验证码 function changeVerifyCode(img){ img.src = "Kaptcha.jpg?"+Math.floor(Math.random()*100); } </script> </head> <body> <p> <form action="result.jsp"> <table> <tr> <td> </td> <td> <img src="Kaptcha.jpg" onclick="changeVerifyCode(this)" style="cursor: pointer;"> </td> </tr> <tr> <td> 请输入验证码： </td> <td> <input type="text" name="verifyCode"> </td> </tr> <tr> <td> </td> <td> <input type="submit" value="提交"> </td> </tr> </table> </form> </body> </html>
5、运行项目，显示结果。
6、最后加上异步验证，看输入的验证码是否正确。
1）增加一个验证的Servlet
package cn.luxh.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 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(); } } } }
2）在web.xml中添加这个Servlet的配置
<!-- 检查验证码是否输入正确 --> <servlet> <servlet-name>VerifyServlet</servlet-name> <servlet-class>cn.luxh.servlet.VerifyServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>VerifyServlet</servlet-name> <url-pattern>/VerifyServlet</url-pattern> </servlet-mapping>
3）页面index.jsp
<%@ 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>验证码</title> <script type="text/javascript" src="${pageContext.request.contextPath}/jquery-1.7.2.min.js"></script> <script type="text/javascript"> //点击切换验证码 function changeVerifyCode(img){ img.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}/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 //..... } }, error:function(e){ alert(e); } }); } } </script> </head> <body> <p> <form action="result.jsp"> <table> <tr> <td> </td> <td> <img src="Kaptcha.jpg" onclick="changeVerifyCode(this)" style="cursor: pointer;"> </td> </tr> <tr> <td> 请输入验证码： </td> <td> <input type="text" name="verifyCode" id="verifyCode"> </td> </tr> <tr> <td> </td> <td> <input type="button" value="提交" onclick="doSubmit()"> </td> </tr> </table> </form> </body> </html>
4）运行结果
