验证码生成工具——Jcaptcha

<dependency>  
    <groupId>com.octo.captcha</groupId>  
    <artifactId>jcaptcha</artifactId>  
    <version>2.0-alpha-1</version>  
</dependency>  
<dependency>  
    <groupId>com.octo.captcha</groupId>  
    <artifactId>jcaptcha-integration-simple-servlet</artifactId>  
    <version>2.0-alpha-1</version>  
    <exclusions>  
        <exclusion>  
            <artifactId>servlet-api</artifactId>  
            <groupId>javax.servlet</groupId>  
        </exclusion>  
    </exclusions>  
</dependency>