cn.apiclub.captcha.servlet

类 StickyCaptchaServlet

java.lang.Object

HttpServlet

cn.apiclub.captcha.servlet.StickyCaptchaServlet

public class StickyCaptchaServlet
extends HttpServlet

Builds a CAPTCHA and stores it in the session. This is intended to prevent bots from simply reloading the page and getting new images until one is generated which they can successfully parse. Removal of the session attribute CaptchaServletUtil.NAME will force a new Captcha to be added to the session. (Obviously, this is not a perfect solution as session IDs can simply not be passed.) The size of the image is by default 200x50. This can be customized using the captcha-height and captcha-width init parameters in web.xml. By default the CAPTCHA will expire after 600000ms. This can be overridden using the ttl init parameter, in milliseconds. An example showing all parameters:

    <servlet>
         <servlet-name>StickyCaptcha</servlet-name>
         <servlet-class>nl.captcha.servlet.StickyCaptchaServlet</servlet-class>
         <init-param>
             <param-name>captcha-width</param-name>
             <param-value>400</param-value>
         </init-param>
         <init-param>
             <param-name>captcha-height</param-name>
             <param-value>200</param-value>
         </init-param>
         <init-param>
             <param-name>ttl</param-name>
             <param-value>900000</param-value>
         </init-param>
       </servlet>
 

Since the constructed image is a PNG the servlet mapping should be defined something like this:

     <servlet-mapping>
         <servlet-name>StickyCaptcha</servlet-name>
         <url-pattern>/stickyCaptcha.png</url-pattern>
     </servlet-mapping>

作者:

James Childers

构造器概要

构造器

构造器和说明
StickyCaptchaServlet()

方法概要

方法

限定符和类型	方法和说明
void	doGet(HttpServletRequest req, HttpServletResponse resp) Write out the CAPTCHA image stored in the session.
void	init(ServletConfig config)

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

构造器详细资料

StickyCaptchaServlet

public StickyCaptchaServlet()

方法详细资料

init

public void init(ServletConfig config)
          throws ServletException

抛出:

ServletException

doGet

public void doGet(HttpServletRequest req,
         HttpServletResponse resp)
           throws ServletException,
                  IOException

Write out the CAPTCHA image stored in the session. If not present, generate a new Captcha and write out its image.

抛出:

ServletException

IOException