<!-- guava 限流 -->
<dependency>
?? ? <groupId>com.google.guava</groupId>
?? ? <artifactId>guava</artifactId>
?? ? <version>25.1-jre</version>
</dependency>

@Target({ElementType.PARAMETER, ElementType.METHOD}) ? ?
@Retention(RetentionPolicy.RUNTIME) ? ?
@Documented ? ?
public ?@interface ServiceLimit {?
?? ? String description() ?default "";
}

@Component
@Scope
@Aspect
public class LimitAspect {
?? ?每秒只發(fā)出5個(gè)令牌，此處是單進(jìn)程服務(wù)的限流,內(nèi)部采用令牌捅算法實(shí)現(xiàn)
?? ?private static ? RateLimiter rateLimiter = RateLimiter.create(5.0);
?? ?
?? ?//Service層切點(diǎn) ?限流
?? ?@Pointcut("@annotation(com.itstyle.seckill.common.aop.ServiceLimit)") ?
?? ?public void ServiceAspect() {
?? ??? ?
?? ?}
?? ?
? ? @Around("ServiceAspect()")
? ? public ?Object around(ProceedingJoinPoint joinPoint) {?
? ? ?? ?Boolean flag = rateLimiter.tryAcquire();
? ? ?? ?Object obj = null;
?? ??? ?try {
?? ??? ??? ?if(flag){
?? ??? ??? ??? ?obj = joinPoint.proceed();
?? ??? ??? ?}
?? ??? ?} catch (Throwable e) {
?? ??? ??? ?e.printStackTrace();
?? ??? ?}?
? ? ?? ?return obj;
? ? }?
}

@Override
@ServiceLimit
@Transactional
?? ?public Result startSeckil(long seckillId,long userId) {
?? ??? ?//todo 操作
?? ?}

<dependency>
? ? <groupId>com.google.guava</groupId>
? ? <artifactId>guava</artifactId>
? ? <version>28.1-jre</version>
? ? <optional>true</optional>
</dependency>

@Slf4j
@Configuration
public class RequestInterceptor implements HandlerInterceptor {
    // 根據(jù)字符串分不同的令牌桶, 每天自動(dòng)清理緩存
    private static LoadingCache<String, RateLimiter> cachesRateLimiter = CacheBuilder.newBuilder()
            .maximumSize(1000)  //設(shè)置緩存?zhèn)€數(shù)
            /**
             * expireAfterWrite是在指定項(xiàng)在一定時(shí)間內(nèi)沒有創(chuàng)建/覆蓋時(shí)，會(huì)移除該key，下次取的時(shí)候從loading中取
             * expireAfterAccess是指定項(xiàng)在一定時(shí)間內(nèi)沒有讀寫，會(huì)移除該key，下次取的時(shí)候從loading中取
             * refreshAfterWrite是在指定時(shí)間內(nèi)沒有被創(chuàng)建/覆蓋，則指定時(shí)間過后，再次訪問時(shí)，會(huì)去刷新該緩存，在新值沒有到來之前，始終返回舊值
             * 跟expire的區(qū)別是，指定時(shí)間過后，expire是remove該key，下次訪問是同步去獲取返回新值；
             * 而refresh則是指定時(shí)間后，不會(huì)remove該key，下次訪問會(huì)觸發(fā)刷新，新值沒有回來時(shí)返回舊值
             */
            .expireAfterAccess(1, TimeUnit.HOURS)
            .build(new CacheLoader<String, RateLimiter>() {
                @Override
                public RateLimiter load(String key) throws Exception {
                    // 新的字符串初始化 (限流每秒2個(gè)令牌響應(yīng))
                    return RateLimiter.create(2);
                }
            });
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        log.info("request請求地址path[{}] uri[{}]", request.getServletPath(), request.getRequestURI());
        try {
            String str = "hello";
            // 令牌桶
            RateLimiter rateLimiter = cachesRateLimiter.get(str);
            if (!rateLimiter.tryAcquire()) {
                System.out.println("too many requests.");
                return false;
            }
        } catch (Exception e) {
            // 解決攔截器的異常，全局異常處理器捕獲不到的問題
            request.setAttribute("exception", e);
            request.getRequestDispatcher("/error").forward(request, response);
        }
        return true;
    }
}

@RestController
@RequestMapping(value = "user")
public class UserController {
    @GetMapping
    public Result test2(){
        System.out.println("1111");
        return new Result(true,200,"");
    }
}

RateLimiter r = RateLimiter.create(5); //項(xiàng)目啟動(dòng)，直接允許5個(gè)令牌

RateLimiter r = RateLimiter.create(2, 3, TimeUnit.SECONDS); //項(xiàng)目啟動(dòng)后3秒后才會(huì)到達(dá)設(shè)置的2個(gè)令牌

TimeUnit.SECONDS);` //項(xiàng)目啟動(dòng)后3秒后才會(huì)到達(dá)設(shè)置的2個(gè)令牌