使用谷歌的kaptcha验证码被破解了

public class ChineseText extends Configurable implements TextProducer {

	public String getText() {
		int length = getConfig().getTextProducerCharLength();
		char[] chars = getConfig().getTextProducerCharString();
		String finalWord = "", firstWord = "";
		String[] array = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
				"a", "b", "c", "d", "e", "f" };

		Random rand = new Random();

		for (int i = 0; i < length; i++) {
			switch (rand.nextInt(3)) {
			case 1:
				firstWord = String.valueOf(chars[rand.nextInt(chars.length)]);
				break;
			case 2:
				int r1,
				r2,
				r3,
				r4;
				String strH,
				strL;// high&low
				r1 = rand.nextInt(3) + 11; // 前闭后开[11,14)
				if (r1 == 13) {
					r2 = rand.nextInt(7);
				} else {
					r2 = rand.nextInt(16);
				}

				r3 = rand.nextInt(6) + 10;
				if (r3 == 10) {
					r4 = rand.nextInt(15) + 1;
				} else if (r3 == 15) {
					r4 = rand.nextInt(15);
				} else {
					r4 = rand.nextInt(16);
				}

				strH = array[r1] + array[r2];
				strL = array[r3] + array[r4];

				byte[] bytes = new byte[2];
				bytes[0] = (byte) (Integer.parseInt(strH, 16));
				bytes[1] = (byte) (Integer.parseInt(strL, 16));

				try {
					firstWord = new String(bytes, "GB2312");
				} catch (UnsupportedEncodingException e) {
					e.printStackTrace();
				}
				break;
			default:
				firstWord = String.valueOf(chars[rand.nextInt(chars.length)]);
				break;
			}
			finalWord += firstWord;
		}
		return finalWord;
	}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">
	<!-- 验证码 -->
	<bean id="captchaProducer" class="com.google.code.kaptcha.impl.DefaultKaptcha">
		<property name="config">
			<bean class="com.google.code.kaptcha.util.Config">
				<constructor-arg>
					<props>
						<prop key="kaptcha.textproducer.font.color">blue</prop>
						<prop key="kaptcha.noise.color">blue</prop>
						<prop key="kaptcha.border">no</prop>
						<prop key="kaptcha.textproducer.char.space">4</prop>
						<prop key="kaptcha.textproducer.impl">com.web.ChineseText</prop>
						<prop key="kaptcha.textproducer.font.names">宋体,楷体,微软雅黑</prop>
					</props>
				</constructor-arg>
			</bean>
		</property>
	</bean>
</beans>