google的验证码 东师理想

先下载  kaptcha-2.3.2.jar 包，maven获取代码：

<!-- 验证码 -->
        <dependency>
            <groupId>com.google.code</groupId>
            <artifactId>kaptcha</artifactId>
            <version>2.3.2</version>
        </dependency>

web.xml增加如下代码

<!-- google的验证码插件 -->
  <servlet> 
        <servlet-name>Kaptcha</servlet-name> 
        <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
        <!-- 全都要数字 -->
        <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>
        <init-param>
            <param-name>kaptcha.border</param-name>
            <param-value>no</param-value>
        </init-param>
        <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>
        <init-param>  
            <param-name>kaptcha.textproducer.font.size</param-name>  
            <param-value>25</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>
          </servlet>

       <servlet-mapping>
           <servlet-name>Kaptcha</servlet-name>
           <url-pattern>/kaptcha.jpg</url-pattern> 
       </servlet-mapping>

前台jsp显示：

<dd>验证码：</dd>
                    <dd>
                        <input type="text" id="yzm" name="yzm" class="inputyzm" maxlength="4"/>
                        <img style="padding-left: 8px; margin-bottom:8px; height:25px;" id="yzmimg" src="<%=basePath%>kaptcha.jpg" />
                    </dd>

后台controller验证

//检查验证码
               String yzm=request.getParameter("yzm");  
               String kaptchaExpected = (String)request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY); 
           
               if(!yzm.equals(kaptchaExpected))
            {
                   responseTxt("2");
                   return;
            }