java實現限流

時間 2019-12-05

標籤 java 實現限流欄目 Java 简体版

原文原文鏈接

問題產生,當調用一個接口很頻繁的時候，好比每秒調用一個接口100次。業務提如今搶購等。這時咱們的服務器處理不過來就會拒絕服務，宕機等等。。。顯然這不是咱們須要的。json

所以產生了限流這個。限流是什麼呢，就是我只是接收那麼多，多的就是等待，排隊，或者拒絕，然你等待，不進入服務。。。服務器

直接上代碼:併發

@Inherited
@Documented
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface RateLimit {
    /**
     * 默認每秒支持100個
     * @return
     */
    int limintNum() default 100;
}

/**
 * 限流 切面枚舉實現
 *
 * @author mingge
 *
 */
@Component
@Scope
@Aspect
@Slf4j
public class RateLimitAspect {

    /**
     * //用來存放不一樣接口的RateLimiter(key爲接口名稱，value爲RateLimiter)
     */
    private ConcurrentHashMap<String, RateLimiter> map = new ConcurrentHashMap<>();

    private static final String POINT = "execution (* com.mingge..*.controller..*.*(..))";

    private static ObjectMapper objectMapper = new ObjectMapper();

    private RateLimiter rateLimiter;

    @Autowired
    private HttpServletResponse response;

    @Pointcut(POINT)
    public void serviceLimit() {
    }

    @Around("serviceLimit()")
    public Object around(ProceedingJoinPoint joinPoint) throws NoSuchMethodException {
        Object obj = null;
        //獲取攔截的方法名
        Signature sig = joinPoint.getSignature();
        //獲取攔截的方法名
        MethodSignature msig = (MethodSignature) sig;
        //返回被織入增長處理目標對象
        Object target = joinPoint.getTarget();
        //爲了獲取註解信息
        Method currentMethod = target.getClass().getMethod(msig.getName(), msig.getParameterTypes());
        //獲取註解信息
        RateLimit annotation = currentMethod.getAnnotation(RateLimit.class);
        //獲取註解每秒加入桶中的token
        int limitNum = annotation.limintNum();
        // 註解所在方法名區分不一樣的限流策略
        String functionName = msig.getName();

        //獲取rateLimiter
        if(map.containsKey(functionName)){
            rateLimiter = map.get(functionName);
        }else {
            map.put(functionName, RateLimiter.create(limitNum));
            rateLimiter = map.get(functionName);
        }
        try {
            if (rateLimiter.tryAcquire()) {
                //執行方法
                obj = joinPoint.proceed();
            } else {
                BaseVO vo=new BaseVO();
                vo.setCode(100001);
                vo.setMessage("系統繁忙，請稍後再試！");
                //拒絕了請求（服務降級）
                String result = objectMapper.writeValueAsString(vo);
                log.info("拒絕了請求：" + result);
                outErrorResult(result);
            }
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }
        return obj;
    }
    //將結果返回
    public void outErrorResult(String result) {
        response.setContentType("application/json;charset=UTF-8");
        try (ServletOutputStream outputStream = response.getOutputStream()) {
            outputStream.write(result.getBytes("utf-8"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    static {
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    }

}