令牌环桶算法的使用案例

import com.google.common.util.concurrent.Monitor;
import com.google.common.util.concurrent.RateLimiter;

import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;

/**

 * @create 2021-02-15 19:21

 * @desc 令牌环桶算法的使用案例

 **/
public class RateLimiterTokenBucket
{
   //当前活动的商品数量
   private final static int MAX = 100;

   //订单编号
   private int orderID;

   //单位时间内（每秒）只允许 10 个用户能够抢购到商品，也就是说“订单服务”将会被匀速地调用
   private final RateLimiter rateLimiter = RateLimiter.create(10.0D);

   private Monitor bookOrderMonitor = new Monitor();

   public void bookOrder(Consumer consumer) throws NoProductionException,OrderFailException
   {
      // 如果当前商品有库存，则执行抢购操作
      if( bookOrderMonitor.enterIf(new Monitor.Guard(bookOrderMonitor)
      {
         @Override
         public boolean isSatisfied()
         {
            return orderID < MAX;
         }
      }))
      {
         try
         {
            //抢购商品，最多等待 100 毫秒
            if(  !rateLimiter.tryAcquire(100, TimeUnit.MILLISECONDS))
            {
               // 如果在 100 毫秒之内抢购仍然失败，则抛出订单失败的异常
               throw  new OrderFailException("book order failed, please try again later.");
            }
            orderID++;
            // 执行订单订购操作
            consumer.accept(orderID);

         }
         finally
         {
            bookOrderMonitor.leave();
         }
      }
      else
      {
         // 如果当前没有库存，则抛出没有商品的异常，该异常将不会再次进行尝试动作
         throw new NoProductionException("No available production now.");
      }
   }

}

-------------------------------------

/**

 * @create 2021-02-15 23:45

 * @desc 自定义异常

 **/
public class OrderFailException extends Exception
{
   public OrderFailException(String message)
   {
      super(message);
   }
}

------------------------------------------

/**

 * @create 2021-02-15 19:29

 * @desc 自定义异常

 **/
public class NoProductionException extends Exception
{
   public NoProductionException(String message)
   {
      super(message);
   }
}