使用Kaptcha这个验证码框架用起来，比自己写简单
首先设置maven项目：
<dependency><groupId>com.github.penggle</groupId><artifactId>kaptcha</artifactId><version>2.3.2</version></dependency>
然后配置WEB-INF下的web.xml
<!DOCTYPE web-app PUBLIC"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN""/dtd/web-app_2_3.dtd" ><web-app><display-name>Archetype Created Web Application</display-name><servlet-mapping><servlet-name>kaptchaDemo</servlet-name><url-pattern>/kaptcha</url-pattern></servlet-mapping><servlet><servlet-name>kaptchaDemo</servlet-name><servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class><init-param><param-name>kaptcha.border</param-name><param-value>no</param-value></init-param><init-param><param-name>kaptcha.textproducer.font.color</param-name><param-value>red</param-value></init-param><init-param><param-name>kaptcha.image.width</param-name><param-value>80</param-value></init-param><init-param><param-name>kaptcha.image.height</param-name><param-value>30</param-value></init-param><init-param><param-name>kaptcha.textproducer.char.string</param-name><param-value>0123456789</param-value></init-param><init-param><param-name>kaptcha.textproducer.char.length</param-name><param-value>4</param-value></init-param><init-param><param-name>kaptcha.textproducer.char.space</param-name><param-value>3</param-value></init-param><init-param><param-name>kaptcha.textproducer.font.size</param-name><param-value>24</param-value></init-param><!-- <init-param>--><!-- <param-name>kaptcha.noise.impl</param-name>--><!-- <param-value>com.google.code.kaptcha.impl.NoNoise</param-value>--><!-- </init-param>--></servlet></web-app>
其中对应的jsp页面如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><base href="<%=basePath%>"><title>kaptchaDemo</title><style type="text/css">.code_a{color: #0000ff;font-size: 12px;text-decoration: none;cursor: pointer;}#imgCode{cursor: pointer;}</style><script type="text/javascript">function changeCode(){var imgCode = document.getElementById("imgCode");imgCode.src = "kaptcha?"+Math.random();}</script></head><body><form action="login" method="post"><label>验证码：</label><input type="text" id="inCode" name="inCode" /><img src="kaptcha" align="center" id="imgCode" onclick="changeCode()" /><a class="code_a" onclick="changeCode()">换一张</a><br /><input type="submit" value="登录"/></form></body></html>
这里src请求的是kaptcha的url。这里这个框架里面实现了一个Servlet，通过配置文件的方式，对某些属性进行设置（这里不用说了，肯定是反射）
程序运行截图如下：
输入错误时，依旧是这个界面，但输入正确后！
下面是关于他的验证方面的代码：
LoginServlet.java
import com.google.code.kaptcha.Constants;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;@WebServlet(value = "/login")public class LoginServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doPost(request, response);}protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String vailCode = request.getSession().getAttribute(Constants.KAPTCHA_SESSION_KEY).toString().toLowerCase();String inCode = request.getParameter("inCode").toLowerCase();if(inCode.equals(vailCode)){response.sendRedirect("success.jsp");}else{String url = request.getHeader("Referer");response.sendRedirect(url);}}}
