利用AOP手写一个简单的熔断和限流

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MAVEN依赖

<!-- aspectj -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>1.9.2</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.9.2</version>
        </dependency>

注解类

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RateLimiter {

    int timeout() default -1;
	int count() default -1;
}

AOP处理类

@Component
@Aspect
public class RatelimiterAop {
	  private static ConcurrentHashMap<String, Semaphore> LIMITER = new ConcurrentHashMap<>();
    @Pointcut("@annotation(RateLimiter)")
    public void point() {

    }

    @Around("point()")
    public Object limit(ProceedingJoinPoint proceedingJoinPoint) {
        MethodSignature methodSignature = (MethodSignature) proceedingJoinPoint.getSignature();
        RateLimiter limit = methodSignature.getMethod().getDeclaredAnnotation(RateLimiter.class);
        if (limit.timeout() > 0) {
            ExecutorService es = Executors.newFixedThreadPool(2);
            Future future = es.submit(() -> {
                try {
                    return proceedingJoinPoint.proceed();
                } catch (Throwable throwable) {
                    return null;
                }
            });
            final Object obj;
            try {
                obj = future.get(limit.timeout(), TimeUnit.MILLISECONDS);
                return obj;
            } catch (Exception e) {
                future.cancel(true);
                throw new RuntimeException("处理超时");
            }

        }else if (limit.count() > 0) {
            // key unique.
            String cacheKey = proceedingJoinPoint.getTarget().getClass().getName() + "::" + methodSignature.getName()
                    + "::" + Arrays.toString(methodSignature.getParameterNames());
            LIMITER.putIfAbsent(cacheKey, new Semaphore(limit.count()));
            System.out.println(cacheKey);

            Semaphore semaphore = LIMITER.get(cacheKey);
            try {
                semaphore.acquire();
                proceedingJoinPoint.proceed();
            } catch (Throwable throwable) {
               throw  new RuntimeException("请求异常");
            } finally {
                // 释放
                if (null != semaphore) {
                    semaphore.release();
                }
            }

        }


        try {
            return proceedingJoinPoint.proceed();
        } catch (Throwable throwable) {
            return null;
        }
    }

测试

@RestController
public class TestController {
    @RateLimiter(timeout = 100)
    @PostMapping(value = "/test")
    public void test(){
        try {
            Random random = new Random();
            int time = random.nextInt(200);
            System.out.println(time + "ms");
            Thread.sleep(time);
            System.out.println("the end");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

来源：oschina

链接：https://my.oschina.net/u/2486137/blog/3153100

标签

limiter

java

aspectj