kaptcha验证码组件使用简介

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

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：

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

3.页面调用

4.在submit的action方法中进行验证码校验

5.实现页面验证码刷新

二、Spring mvc项目中使用kaptcha

1.添加captchaProducer bean定义

<!-- 配置kaptcha验证码 -->  <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">100</prop>                      <prop key="kaptcha.image.height">50</prop>                      <prop key="kaptcha.noise.impl">com.google.code.kaptcha.impl.NoNoise</prop>                      <prop key="kaptcha.textproducer.char.string">0123456789abcdefghijklmnopqrstuvwxyz</prop>                      <prop key="kaptcha.textproducer.char.length">4</prop>                  </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;     @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

@Controller  @RequestMapping("/login")  public class LoginController {      @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      }  }