验证码插件kaptcha的jsp使用

1，去http://code.google.com/p/kaptcha/downloads/list下载kaptcha-2.3.2.zip包，或直接【点此下载】解压交其中的kaptcha-2.3.2.jar 导入项目目录下lib

2，向web.xml里添加servlet

<servlet>
        <servlet-name>Kaptcha</servlet-name>
        <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
        
    </servlet>
    <servlet-mapping>
        <servlet-name>Kaptcha</servlet-name>
        <url-pattern>/kaptcha.jpg</url-pattern>
    </servlet-mapping>

3，服务端程序验证功能

@RequestMapping("/kaptcha.do")
    public void kaptcha(HttpServletRequest request, HttpServletResponse response) {
    String kaptchaExpected = (String) request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
    String kaptchaReceived = request.getParameter("kaptcha"); //获取填写的验证码内容
    if (kaptchaReceived == null || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)) {  //判断内容是否相同
        try {
        response.getWriter().print("validation code is wrong.");
        } catch (IOException e) {
        e.printStackTrace();
        }
    } else {
        try {
        response.getWriter().print("validation code is right.");
        } catch (IOException e) {
        e.printStackTrace();
        }
    }
    }

4，jsp代码

为了便于测试。本文用JQuery添加属性

<script type="text/javascript" src="page/js/jquery.js"></script>
<script type="text/javascript">
    $(function(){
        $('#kaptchaImage').click(function () { 
            $(this).attr('src', 'kaptcha.jpg?' + Math.floor(Math.random()*100) ); 
        });
    });
</script>

 <form action="kaptcha.do">
    <img src="kaptcha.jpg" id="kaptchaImage"/>
    <input type="text" name="kaptcha" value=""/><br/>
    <button type="submit">提交</button>
 </form>