推荐一款java的验证码组件

使用方法：

        Kaptcha

        com.google.code.kaptcha.servlet.KaptchaServlet

            kaptcha.producer.impl

            com.google.code.kaptcha.impl.DefaultKaptcha

                            kaptcha.textproducer.font.color

                            black

                            kaptcha.textproducer.char.space

                            10

                            kaptcha.border

                            no

                            kaptcha.border.thickness

                            0

                            kaptcha.textproducer.font.size

                            35

                            kaptcha.textproducer.char.length

                            4

            kaptcha.image.width

            150

            kaptcha.image.height

            50

                            kaptcha.background.clear.from

                            255,255,255

                            kaptcha.background.clear.to

                            255,255,255

            kaptcha.textproducer.char.string

            0123456789

            kaptcha.textproducer.font.names

            Arial Black

            kaptcha.noise.impl

            com.google.code.kaptcha.impl.NoNoise

        Kaptcha

        /kaptcha.jpg

function refresh() {

                  document.getElementById('img').src="kaptcha.jpg?"+Math.random();

}