Kaptcha验证码的使用

Kaptcha是一个基于SimpleCaptcha的验证码开源项目。

官网地址：http://code.google.com/p/kaptcha/

 

kaptcha的使用比较方便，只需添加jar包依赖之后简单地配置就可以使用了。kaptcha所有配置都可以通过web.xml来完成，如果你的项目中使用了Spring MVC，那么则有另外的一种方式来实现。

 

一、简单的jsp-servlet项目

1.添加jar包依赖

如果你使用maven来统一管理jar包，则在工程的pom.xml中添加dependency

 <dependency>
     <groupId>com.google.code.kaptchagroupId>
     <artifactId>kaptchaartifactId>
     <version>2.3.2version>
 dependency>

如果是非maven管理的项目，则直接在官网下载kaptcha的jar包，然后添加到项目lib库中，下载地址：http://code.google.com/p/kaptcha/downloads/list

 

 

2.配置web.xml

上面说了，kaptcha都是在web.xml中配置，我们必须在web.xml中配置kaptcha的servlet，具体如下：

 <servlet>
     <servlet-name>Kaptchaservlet-name>
     <servlet-class>com.google.code.kaptcha.servlet.KaptchaServletservlet-class>
 servlet>
 <servlet-mapping>
     <servlet-name>Kaptchaservlet-name>
     <url-pattern>/kaptcha.jpgurl-pattern>
 servlet-mapping>

其中servlet的url-pattern可以自定义。

 

kaptcha所有的参数都有默认的配置，如果我们不显示配置的话，会采取默认的配置。

如果要显示配置kaptcha，在配置kaptcha对应的Servlet时，在init-param增加响应的参数配置即可。示例如下：

 <servlet>
     <servlet-name>Kaptchaservlet-name>
     <servlet-class>com.google.code.kaptcha.servlet.KaptchaServletservlet-class>
     <init-param>
         <param-name>kaptcha.image.widthparam-name>
         <param-value>200param-value>
         <description>Width in pixels of the kaptcha image.description>
     init-param>
     <init-param>
         <param-name>kaptcha.image.heightparam-name>
         <param-value>50param-value>
         <description>Height in pixels of the kaptcha image.description>
     init-param>
     <init-param>
         <param-name>kaptcha.textproducer.char.lengthparam-name>
         <param-value>4param-value>
         <description>The number of characters to display.description>
     init-param>
     <init-param>
         <param-name>kaptcha.noise.implparam-name>
         <param-value>com.google.code.kaptcha.impl.NoNoiseparam-value>
         <description>The noise producer.description>
     init-param>
 servlet>

具体的配置参数参见：http://code.google.com/p/kaptcha/wiki/ConfigParameters

 

3.页面调用

 <form action="submit.action">
     <input type="text" name="kaptcha" value="" /><img src="kaptcha.jpg" />
 form>

 

4.在submit的action方法中进行验证码校验

 //从session中取出servlet生成的验证码text值
 String kaptchaExpected = (String)request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
 //获取用户页面输入的验证码
 String kaptchaReceived = request.getParameter("kaptcha");
 //校验验证码是否正确
 if (kaptchaReceived == null || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)){
     setError("kaptcha", "Invalid validation code.");
 }

注：确保JDK设置了 -Djava.awt.headless=true

 

5.实现页面验证码刷新

 <img src="kaptcha.jpg" width="200" id="kaptchaImage" title="看不清，点击换一张" />
 <script type="text/javascript">
     $(function() {
         $('#kaptchaImage').click(function() {$(this).attr('src','kaptcha.jpg?' + Math.floor(Math.random() * 100));});
     });
 script>
 <br /><small>看不清，点击换一张small>

注：为了避免浏览器的缓存，可以在验证码请求url后添加随机数

 

二、Spring mvc项目中使用kaptcha

1.添加captchaProducer bean定义

 <bean id="captchaProducer" class="com.google.code.kaptcha.impl.DefaultKaptcha">
     <property name="config">
         <bean class="com.google.code.kaptcha.util.Config">
             <constructor-arg type="java.util.Properties">
                 <props>
                     <prop key="kaptcha.image.width">100prop>
                     <prop key="kaptcha.image.height">50prop>
                     <prop key="kaptcha.noise.impl">com.google.code.kaptcha.impl.NoNoiseprop>
                     <prop key="kaptcha.textproducer.char.string">0123456789abcdefghijklmnopqrstuvwxyzprop>
                     <prop key="kaptcha.textproducer.char.length">4prop>
                 props>
             constructor-arg>
         bean>
     property>
 bean>

2.生成验证码的Controller

 import java.awt.image.BufferedImage;

 import javax.imageio.ImageIO;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.servlet.ModelAndView;

 import com.google.code.kaptcha.Constants;
 import com.google.code.kaptcha.Producer;

 /**
  * ClassName: CaptchaImageCreateController
  * Function: 生成验证码Controller.
  * date: 2013-12-10 上午11:37:42
  *
  * @author [email protected]
  */
 @Controller
 public class CaptchaImageCreateController {
     private Producer captchaProducer = null;

     @Autowired
     public void setCaptchaProducer(Producer captchaProducer){
         this.captchaProducer = captchaProducer;
     }

     @RequestMapping("/kaptcha.jpg")
     public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception{
         // Set to expire far in the past.
         response.setDateHeader("Expires", 0);
         // Set standard HTTP/1.1 no-cache headers.
         response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
         // Set IE extended HTTP/1.1 no-cache headers (use addHeader).
         response.addHeader("Cache-Control", "post-check=0, pre-check=0");
         // Set standard HTTP/1.0 no-cache header.
         response.setHeader("Pragma", "no-cache");

         // return a jpeg
         response.setContentType("image/jpeg");

         // create the text for the image
         String capText = captchaProducer.createText();

         // store the text in the session
         request.getSession().setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);

         // create the image with the text
         BufferedImage bi = captchaProducer.createImage(capText);

         ServletOutputStream out = response.getOutputStream();

         // write the data out
         ImageIO.write(bi, "jpg", out);
         try {
             out.flush();
         } finally {
             out.close();
         }
         return null;
     }
 }

 

3.校验用户输入的Controller

 /**
  * ClassName: LoginController
  * Function: 登录Controller.
  * date: 2013-12-10 上午11:41:43
  *
  * @author [email protected]
  */
 @Controller
 @RequestMapping("/login")
 public class LoginController {

     /**
      * loginCheck:ajax异步校验登录请求.
      *
      * @author [email protected]
      * @param request
      * @param username 用户名
      * @param password 密码
      * @param kaptchaReceived 验证码
      * @return 校验结果
      * @since 2013-12-10
      */
     @RequestMapping(value = "check", method = RequestMethod.POST)
     @ResponseBody
     public String loginCheck(HttpServletRequest request,
             @RequestParam(value = "username", required = true) String username,
             @RequestParam(value = "password", required = true) String password,
             @RequestParam(value = "kaptcha", required = true) String kaptchaReceived){
         //用户输入的验证码的值
         String kaptchaExpected = (String) request.getSession().getAttribute(
                 com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
         //校验验证码是否正确
         if (kaptchaReceived == null || !kaptchaReceived.equals(kaptchaExpected)) {
             return "kaptcha_error";//返回验证码错误
         }
         //校验用户名密码
         // ……
         // ……
         return "success"; //校验通过返回成功
     }
 }