public class ServiceFilter implements Filter {
 
 private static final int MAX_COUNT = 20;
 
 private AtomicInteger filterCount = 0;

 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  System.out.println("before"+filterCount);
  if(filterCount > MAX_COUNT) {
   //请求个数太多，跳转到排队页面
   request.getRequestDispatcher("index.jsp").forward(request, response);
  } else {
   //请求个数加1
   filterCount.incrementAndGet();

   chain.doFilter(request, response);
   //访问结束，请求个数减1
   filterCount.decrementAndGet();
  }
 }

public class RateLimiterUtils {
 private static Logger logger = LoggerFactory.getLogger(RateLimiterUtils.class);
 private static final ConcurrentHashMap<String, RateLimiter> resourceLimitMap = 
   new ConcurrentHashMap<String, RateLimiter>();
 
 /**
  * 限流
  * @param resource 需要限流的对象的标识
  * @return true表示得到了许可，没有达到限流阀值，false表示得不到许可，达到了限流阀值。
  * @author: hejinen
  * @date:2016年10月19日 上午11:08:49
  */
 public static boolean rateLimit(String resource) {
  RateLimiter limit = getRateLimit(resource);
  return limit.tryAcquire();
 }
    /**
  * 获取某个需限流对象的RateLimiter，如不存在则创建新的
  * @param resouce 需要限流的对象标识
  */
 public static RateLimiter getRateLimit(String resource) {
  RateLimiter limit = resourceLimitMap.get(resource); 
  if(limit == null) {
   synchronized(RateLimiterUtils.class) {
    limit = resourceLimitMap.get(resource);
    double qps = getQpsByResource(resource);
    if(limit == null) {
     limit = RateLimiter.create(qps);
     resourceLimitMap.put(resource, limit);
     LoggerUtil.info(RateLimiterUtils.class, "create rate limiter for key:{0},QPS:{1}", resource,qps);
    }
   }
  }
  return resourceLimitMap.get(resource);
 }
}