Cage验证码生成器快速上手

Cage小巧，好用。这里在官方基础例子基础上做了扩展：

  package com.lavasoft.ntv.web.common; 
 import com.github.cage.IGenerator; 
 import java.util.Random; 
/**
  * 验证码生成器 
  * 
  * @author leizhimin 14-5-5 下午2:42 
  */ 
 public class MyTokenGenerator implements IGenerator<String> { 
     private int length = 4; 
     private String charsetdir = "23456789abcdefghigkmnpqrstuvwxyzABCDEFGHIGKLMNPQRSTUVWXYZ"; 
     private static final Random r = new Random(); 
     public MyTokenGenerator() { 
     } 
     public MyTokenGenerator(int length, String charsetdir) { 
         this.length = length; 
         this.charsetdir = charsetdir; 
     } 
     @Override 
     public String next() { 
         StringBuffer sb = new StringBuffer(); 
         int len = charsetdir.length(); 
         for (int i = 0; i < length; i++) { 
             sb.append(charsetdir.charAt(r.nextInt(len - 1))); 
         } 
         return sb.toString(); 
     } 
     public static void main(String[] args) { 
         MyTokenGenerator t = new MyTokenGenerator(); 
         for (int i = 0; i < 100; i++) { 
             System.out.println(t.next()); 
         } 
     } 
}

  package com.lavasoft.ntv.web.servlet; 
 import com.github.cage.Cage; 
 import com.lavasoft.ntv.web.common.MyTokenGenerator; 
 import javax.servlet.ServletException; 
 import javax.servlet.http.HttpServlet; 
 import javax.servlet.http.HttpServletRequest; 
 import javax.servlet.http.HttpServletResponse; 
 import javax.servlet.http.HttpSession; 
 import java.io.IOException; 
 public class CaptchaServlet extends HttpServlet { 
     private static final long serialVersionUID = 1490947492185481844L; 
     private static final Cage cage = new Cage(null,null,null,null,null, new MyTokenGenerator(),null); 
     /** 
      * Generates a captcha token and stores it in the session. 
      * 
      * @param session where to store the captcha. 
      */ 
     public static void generateToken(HttpSession session) { 
         String token = cage.getTokenGenerator().next(); 
         session.setAttribute("captchaToken", token); 
         markTokenUsed(session, false); 
     } 
     /** 
      * Used to retrieve previously stored captcha token from session. 
      * 
      * @param session where the token is possibly stored. 
      * @return token or null if there was none 
      */ 
     public static String getToken(HttpSession session) { 
         Object val = session.getAttribute("captchaToken"); 
         return val != null ? val.toString() : null; 
     } 
     /** 
      * Marks token as used/unused for image generation. 
      * 
      * @param session where the token usage flag is possibly stored. 
      * @param used    false if the token is not yet used for image generation 
      */ 
     protected static void markTokenUsed(HttpSession session, boolean used) { 
         session.setAttribute("captchaTokenUsed", used); 
     } 
     /** 
      * Checks if the token was used/unused for image generation. 
      * 
      * @param session where the token usage flag is possibly stored. 
      * @return true if the token was marked as unused in the session 
      */ 
     protected static boolean isTokenUsed(HttpSession session) { 
         return !Boolean.FALSE.equals(session.getAttribute("captchaTokenUsed")); 
     } 
     @Override 
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
             throws ServletException, IOException { 
         HttpSession session = req.getSession(false); 
         String token = session != null ? getToken(session) : null; 
         if (token == null || isTokenUsed(session)) { 
             resp.sendError(HttpServletResponse.SC_NOT_FOUND,"Captcha not found."); 
             return; 
         } 
         setResponseHeaders(resp); 
         markTokenUsed(session, true); 
         cage.draw(token, resp.getOutputStream()); 
     } 
     /** 
      * Helper method, disables HTTP caching. 
      * 
      * @param resp response object to be modified 
      */ 
     protected void setResponseHeaders(HttpServletResponse resp) { 
         resp.setContentType("image/" + cage.getFormat()); 
         resp.setHeader("Cache-Control", "no-cache, no-store"); 
         resp.setHeader("Pragma", "no-cache"); 
         long time = System.currentTimeMillis(); 
         resp.setDateHeader("Last-Modified", time); 
         resp.setDateHeader("Date", time); 
         resp.setDateHeader("Expires", time); 
     } 
}

 <%--
   Created by IntelliJ IDEA. 
   User: leizhimin 14-5-5 下午12:18 
--%>
<%@page import="com.lavasoft.ntv.web.servlet.CaptchaServlet"%><%@
         page contentType="text/html" pageEncoding="UTF-8"%><% 
     boolean showGoodResult; 
     boolean showBadResult; 
     if ("POST".equals(request.getMethod())) { 
         String sessionToken = CaptchaServlet.getToken(session); 
         String requestToken = request.getParameter("captcha"); 
         showGoodResult = sessionToken != null && sessionToken.equals(requestToken); 
         showBadResult = !showGoodResult; 
     } else { 
         showGoodResult = showBadResult = false; 
     } 
     CaptchaServlet.generateToken(session); 
%><!DOCTYPE html>
 <html xmlns="http://www.w3.org/1999/xhtml"> 
 <head> 
     <meta charset="UTF-8" /> 
     <title>Captcha Reader</title> 
 </head> 
 <body> 
<%  if (showGoodResult) {%>
 <h1 style="color: green;">Your kung fu is good!</h1> 
<%  } else if (showBadResult) {%>
 <h1 style="color: red;">This is not right. Try again!</h1> 
<%  } %>
 <p>Type in the word seen on the picture</p> 
 <form action="" method="post"> 
     <input name="captcha" type="text" autocomplete="off" /> 
     <input type="submit" /> 
 </form> 
 <img alt="captcha image" src="/ntv/captcha" width="120px" height="30px"/> 
 </body> 
 </html> 

  <servlet> 
     <servlet-name>captcha</servlet-name> 
     <servlet-class>com.lavasoft.ntv.web.servlet.CaptchaServlet</servlet-class> 
 </servlet> 
 <servlet-mapping> 
     <servlet-name>captcha</servlet-name> 
     <url-pattern>/captcha</url-pattern> 
 </servlet-mapping> 