验证码（google kaptcha）

google kaptcha的使用

下载jar文件

http://kaptcha.googlecode.com/files/kaptcha-2.3.2.zip

配置web.xml

<servlet>
  <servlet-name>Kaptcha</servlet-name>
  <servlet-class>
   com.google.code.kaptcha.servlet.KaptchaServlet
  </servlet-class>
  <init-param>
   <param-name>kaptcha.image.width</param-name>
   <param-value>65</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.length</param-name>
   <param-value>4</param-value>
  </init-param>
  <!-- 字体大小 -->
  <init-param>
   <param-name>kaptcha.textproducer.font.size</param-name>
   <param-value>25</param-value>
  </init-param>
  <!-- 字体颜色 -->
  <init-param>
   <param-name>kaptcha.textproducer.font.color</param-name>
   <param-value>black</param-value>
  </init-param>
  <init-param>
   <param-name>kaptcha.background.impl</param-name>
   <param-value>
    com.google.code.kaptcha.impl.DefaultBackground
   </param-value>
  </init-param>
  <init-param>
   <param-name>kaptcha.obscurificator.impl</param-name>
   <param-value>
    com.google.code.kaptcha.impl.ShadowGimpy
   </param-value>
  </init-param>
  <init-param><!-- 背景颜色 -->
   <param-name>kaptcha.background.clear.to</param-name>
   <param-value>white</param-value>
  </init-param>
  <init-param><!-- 干扰线颜色 -->
   <param-name>kaptcha.noise.color</param-name>
   <param-value>black</param-value>
  </init-param>
    <!-- 如果需要全部数字 -->
        <init-param>     
            <param-name>kaptcha.textproducer.char.string</param-name>     
            <param-value>0123456789</param-value>     
        </init-param> 
        <!-- 去掉干扰线 -->
        <init-param>
            <param-name>kaptcha.noise.impl</param-name>
            <param-value>com.google.code.kaptcha.impl.NoNoise </param-value>
        </init-param>
 </servlet>
 <servlet-mapping>
  <servlet-name>Kaptcha</servlet-name>
  <url-pattern>/kaptcha.jpg</url-pattern>
 </servlet-mapping>

 jsp页面显示

 

<img src="kaptcha.jpg" id="img" onclick="flashImg()"/>
 <form method="post">
  <input type="text" name="codeImg"/>
  <input type="submit" value="提交"/>
 </form>
 <script type="text/javascript">
  function flashImg(){
   document.getElementById("img").src="${pageContext.request.contextPath}/kaptcha.jpg?"+Math.floor(Math.random()*100);
  }
 </script>
 <%
  String c = (String)session.getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
  String parm = (String)request.getParameter("codeImg");
  out.println("param: " + parm + " ? Key: " + c + " : ");
  if (c != null && parm != null) {
   if (c.equals(parm)) {
    out.println("<b>true</b>");
   } else {
    out.println("<b>false</b>");
   }
  }
 %>