kaptcha验证码的简单使用及配置

kaptcha是一个简单易用的验证码生成工具，而且支持中文，你还可以配置其很多属性。 

用法： 

1、首先到http://code.google.com/p/kaptcha/downloads/list把压缩文件下下来，然后把里面的jar文件加到自己的web项目中。 

2在web.xml中配置servlet，代码如下： 

<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</url-pattern>
    </servlet-mapping>

3.页面代码： 

<div id="login" class="container" style="">
        <h2>用户登录</h2>
        <form action="#" method="post" accept-charset="utf-8"
            class="navbar-form pull-left">
            <img src="kaptcha" /> <br>
            <input type="text" name="kaptcha" value="" /> <br>
            <p><a class="btn btn-primary" id="upload_btn">上传 </a>
        </form>
    </div>

4.服务器端代码： 

String kaptchaExpected = (String)request.getSession() .getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
String kaptchaReceived = request.getParamater("kaptcha");
if (kaptchaReceived == null || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)){ setError("kaptcha", "Invalid validation code.");}

以上就完成了kaptcha的一个简单的使用，你还可以根据自己的需要进行更详细的配置

<servlet-name>Kaptcha</servlet-name>
  <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
  <!-- 设置是否有边框 -->
  <init-param>
   <param-name>kaptcha.border</param-name>
   <param-value>yes</param-value>
  </init-param>
  <!-- 设置边框颜色-->
  <init-param>
   <param-name>kaptcha.border.color</param-name>
   <param-value>105,179,90</param-value>
  </init-param>
  <!-- 获取中文 -->
  <init-param>
   <param-name>kaptcha.textproducer.impl</param-name>
   <param-value>org.cric.util.ChineseText</param-value>
  </init-param>
  <!-- 设置字体颜色 -->
  <init-param>
   <param-name>kaptcha.textproducer.font.color</param-name>
   <param-value>black</param-value>
  </init-param>
  <!-- 设置验证码宽度 -->
  <init-param>
   <param-name>kaptcha.image.width</param-name>
   <param-value>130</param-value>
  </init-param>
  <!-- 设置验证码高度 -->
  <init-param>
   <param-name>kaptcha.image.height</param-name>
   <param-value>44</param-value>
  </init-param>
  <!-- 设置字体大小 -->
  <init-param>
   <param-name>kaptcha.textproducer.font.size</param-name>
   <param-value>30</param-value>
  </init-param>
  <!-- 设置字体个数 -->
  <init-param>
   <param-name>kaptcha.textproducer.char.length</param-name>
   <param-value>4</param-value>
  </init-param>
  <!-- 设置字体样式 -->
  <init-param>
   <param-name>kaptcha.textproducer.font.names</param-name>
   <param-value>宋体,楷体,微软雅黑</param-value>
  </init-param>

 </servlet>