图形验证码如何解决集群中使用问题

@RequestMapping(value = "/getKaptchaImage", method = RequestMethod.GET)
    public
    ModelAndView getImage(HttpServletRequest request, HttpServletResponse response) throws Exception{
        HttpSession session = request.getSession();
        Cache<String, String> kaptcha = cacheManager.getCache("kaptcha");
        String code = kaptcha.get(Constants.KAPTCHA_SESSION_KEY);

        System.out.println("******************验证码是: " + code + "******************");
        Producer captchaProducer = (Producer)SpringContextUtils.getBean("captchaProducer");
        response.setDateHeader("Expires", 0);

        // Set standard HTTP/1.1 no-cache headers.
        response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");

        // Set IE extended HTTP/1.1 no-cache headers (use addHeader).
        response.addHeader("Cache-Control", "post-check=0, pre-check=0");

        // Set standard HTTP/1.0 no-cache header.
        response.setHeader("Pragma", "no-cache");

        // return a jpeg
        response.setContentType("image/jpeg");

        // create the text for the image
        String capText = captchaProducer.createText();

        // store the text in the session
        session.setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);
        kaptcha.put(Constants.KAPTCHA_SESSION_KEY, capText);

        // create the image with the text
        BufferedImage bi = captchaProducer.createImage(capText);
        ServletOutputStream out = response.getOutputStream();

        // write the data out
        ImageIO.write(bi, "jpg", out);
        try {
            out.flush();
        } finally {
            out.close();
        }
        return null;
    }

    @RequestMapping(value = "/checkKaptchaImage", method = RequestMethod.POST)
    public
    @ResponseBody
    Map<String, String> checkKaptchaImage(HttpServletRequest request, HttpServletResponse response) throws Exception{
        Map<String, String> returnMap = new HashMap<>();
        Cache<String, String> kaptcha = cacheManager.getCache("kaptcha");
        //从session中取出servlet生成的验证码text值
        String kaptchaExpected = kaptcha.get(Constants.KAPTCHA_SESSION_KEY);
        //获取用户页面输入的验证码
        String kaptchaReceived = request.getParameter("kaptcha");
        //校验验证码是否正确
        returnMap.put("code", "100");
        if (kaptchaExpected == null){
            returnMap.put("status", "expire");
            return returnMap;
        }
        if (!kaptchaReceived.equalsIgnoreCase(kaptchaExpected)){
            returnMap.put("status", "false");
            return returnMap;
        }
        returnMap.put("status", "true");
        return returnMap;
    }

package com.nc.shiro.cache;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.apache.shiro.cache.Cache;
import org.apache.shiro.cache.CacheException;
import org.apache.shiro.cache.CacheManager;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;

public class RedisCacheManager implements CacheManager {

	private static final Logger logger = LoggerFactory
			.getLogger(RedisCacheManager.class);

	@Autowired
	private JedisConnectionFactory connectionFactory;

	private static  RedisRealOPT redisRealOPT;

	// fast lookup by name map
	private final ConcurrentMap<String, Cache> caches = new ConcurrentHashMap<String, Cache>();


	/**
	 * The Redis key prefix for caches
	 */
	private String keyPrefix = "shiro_redis_cache:";

	/**
	 * Returns the Redis session keys
	 * prefix.
	 * @return The prefix
	 */
	public String getKeyPrefix() {
		return keyPrefix;
	}

	/**
	 * Sets the Redis sessions key
	 * prefix.
	 * @param keyPrefix The prefix
	 */
	public void setKeyPrefix(String keyPrefix) {
		this.keyPrefix = keyPrefix;
	}

	@Override
	public <K, V> Cache<K, V>  getCache(String name) throws CacheException {
		logger.debug("获取名称为: " + name + " 的RedisCache实例");

		Cache c = caches.get(name);

		if (c == null) {
			redisRealOPT = new RedisRealOPT();
			redisRealOPT.setJedis(connectionFactory.getShardInfo().createResource());
			redisRealOPT.setExpire(getTTL(name));
			keyPrefix = name + ":";
			// create a new cache instance
			c = new RedisCache<K, V>(redisRealOPT, keyPrefix);

			// add it to the cache collection
			caches.put(name, c);
		}
//		else {
//			((RedisCache) c).getCache().setJedis(connectionFactory.getShardInfo().createResource());
//		}

		return c;
	}


	public JedisConnectionFactory getConnectionFactory() {
		return connectionFactory;
	}

	public void setConnectionFactory(JedisConnectionFactory connectionFactory) {
		this.connectionFactory = connectionFactory;
	}

	private int getTTL(String name){
		//获得路径
		File classPath = new File(this.getClass().getResource("/").getPath());
		File properties = new File(classPath.getPath() + "/cacheManager.properties");
		Properties prop = new Properties();
		try {
			prop.load(new FileInputStream(properties));
			String propertyNames = prop.stringPropertyNames().toString();
			if (propertyNames.contains(name)){
				String value = prop.getProperty(name).trim();
				return Integer.parseInt(value);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}



		return 0;
	}


}