Semaphore并發(fā)包

semaphore是基于計(jì)數(shù)的記號(hào)量,它可以設(shè)定一個(gè)資源的總數(shù)量,基于這個(gè)總數(shù)量,多線程競(jìng)爭(zhēng)獲取許可信號(hào),做自己的申請(qǐng)后,返回許可,并釋放資源.超過總數(shù)量后,線程申請(qǐng)?jiān)S可,信號(hào)將被阻塞,待有資源后,繼續(xù)執(zhí)行
下面是單線程實(shí)現(xiàn):

package cn.easyAccess.core.cache.local;

import java.util.concurrent.Semaphore;

/**
 * @author lqyang
 * @Title: ${file_name}
 * @date 2018/9/511:29
 */
public class semaphoreDemo {

    Semaphore semaphore = new Semaphore(1);

    public void TestSemaphore(){
        try {
            //獲取資源許可數(shù)量
            int var = semaphore.availablePermits();
            if (var <= 0){
                System.out.println(Thread.currentThread().getName()+"資源許可被占用");
            }
            //獲取許可
            semaphore.acquire();
            System.out.println(Thread.currentThread().getName()+"資源許可拿到-->start");
            Thread.sleep(10);
            System.out.println(Thread.currentThread().getName()+"資源處理完畢-->stop");
            //將占用信號(hào)歸還
            semaphore.release();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

}

package cn.easyAccess.core.cache.local;

/**
 * @author lqyang
 * @Title: ${file_name}
 * @date 2018/8/510:49
 */
public class semaphoreTest extends Thread{

    semaphoreDemo semaphoreDemo;

    public semaphoreTest(semaphoreDemo semaphoreDemo){
        super();
        this.semaphoreDemo = semaphoreDemo;
    }

    @Override
    public void run() {
        //TODO
        semaphoreDemo.TestSemaphore();
    }
}

package cn.easyAccess.core.cache.local;

/**
 * @author lqyang
 * @Title: ${file_name}
 * @date 2018/9/511:54
 */
public class demoTest {

    public static void main(String[] args) {
        semaphoreDemo semaphoreDemo = new semaphoreDemo();
        new semaphoreTest(semaphoreDemo).start();
    }
}

執(zhí)行結(jié)果如下:

多線程實(shí)現(xiàn):

for (int i= 1; i< 5; i++){
            new semaphoreTest(semaphoreDemo).start();
}

執(zhí)行結(jié)果如下:

下面是springboot具體實(shí)現(xiàn):

 @GetMapping("/getOrderBuyerInfo")
    public RespApi getOrderBuyerInfo(String keyword){
        //可用資源數(shù)
        int availablePermits = semaphore.availablePermits();
        List<BuyersInfoModel>  buyersInfoModels = new ArrayList<>();
        if (availablePermits > 0){
            logger.info("搶到資源");
        }else {
            logger.info("資源已被占用");
            return RespApi.failure("No resources");
        }
        try{
            //請(qǐng)求占用一個(gè)資源
            semaphore.acquire(1);
            String userId = getUser().getCreateUserId();
            buyersInfoModels = orderService.getOrderShippingInfo(userId,keyword);
        }catch (Exception e){
            e.printStackTrace();
            return RespApi.failure("error");
        }finally {
            //釋放資源
            semaphore.release(1);
        }
        return RespApi.success(buyersInfoModels);
    }

通過semaphore來實(shí)現(xiàn)線程安全。