@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface SlidingWindowLimit {
    /**
     * 限流維度的 SpEL 表達(dá)式
     * 示例：
     * - 按郵箱： "#email"
     * - 按 IP： "#request.remoteAddr"
     * - 按用戶(hù) ID + 郵箱： "#user.id + ':' + #user.email"
     */
    String keySpEL() default "#email";
    /**
     * 窗口大小
     */
    int windowSize() default 60;
    /**
     * 時(shí)間單位
     */
    TimeUnit timeUnit() default TimeUnit.SECONDS;
    /**
     * 窗口內(nèi)最大請(qǐng)求數(shù)
     */
    int maxRequests() default 10;

}

@Aspect
@Component
@Order(Ordered.HIGHEST_PRECEDENCE + 20)
public class SlidingWindowLimitAspect {
    @Resource
    private RedissonClient redissonClient;
    private static final Logger log = LoggerFactory.getLogger(SlidingWindowLimitAspect.class);
    private static final String RATE_LIMIT_PREFIX = "rate_limit";
}

@Around("@annotation(slidingWindowLimit)")
public Object around(ProceedingJoinPoint joinPoint, SlidingWindowLimit slidingWindowLimit) throws Throwable {
    //獲取方法簽名
    MethodSignature signature = (MethodSignature) joinPoint.getSignature();
    Method method = signature.getMethod();
    String methodName = method.getName();
    //判斷是否為Http請(qǐng)求
    ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
    if(attributes == null){
        log.warn("方法 {} 不在 Web 請(qǐng)求上下文中，跳過(guò)限流檢查。", methodName);
        return joinPoint.proceed();
    }
    try {
        Object parseSpEL = parseSpEL(joinPoint, signature, slidingWindowLimit.keySpEL());
        String rateLimitKey = buildRateLimitKey(parseSpEL, slidingWindowLimit);
        if(isRateLimited(rateLimitKey, slidingWindowLimit.windowSize(), slidingWindowLimit.timeUnit(), slidingWindowLimit.maxRequests())){
            throw new RateLimitExceededException("Rate limit exceeded");
        }
        return joinPoint.proceed();
    }catch (RateLimitExceededException e){
        log.warn("方法 {} 觸發(fā)了限流，已拒絕訪問(wèn)。", methodName);
        throw e;
    }catch (Exception e){
        log.error("方法 {} 觸發(fā)了異常，已拒絕訪問(wèn)。", methodName, e);
        throw e;
    }
}

private Object parseSpEL(ProceedingJoinPoint joinPoint,MethodSignature signature, String keySpEL){
    StandardEvaluationContext context = new StandardEvaluationContext();

    Object[] args = joinPoint.getArgs();
    String[] parameterNames = signature.getParameterNames();

    for (int i = 0; i < args.length; i++) {
        if(parameterNames!=null && i< parameterNames.length){
            context.setVariable(parameterNames[i], args[i]);
        }else {
            context.setVariable("arg" + i, args[i]);
        }
    }

    ExpressionParser parser = new SpelExpressionParser();
    return parser.parseExpression(keySpEL).getValue(context);
}

private String buildRateLimitKey(Object keyValue, SlidingWindowLimit slidingWindowLimit){
    if(keyValue == null){
        throw new IllegalArgumentException("限流參數(shù)不能為空");
    }
    return String.format("%s:%s:%s",RATE_LIMIT_PREFIX,slidingWindowLimit.keySpEL(), keyValue);
}

rate_limit:SpEL表達(dá)式:參數(shù)值
↓          ↓         ↓
rate_limit:#email:user@example.com

private boolean isRateLimited(String key, int windowSize, TimeUnit timeUnit, int maxRequests){
    //獲取當(dāng)前時(shí)間數(shù)
    long currentTime = System.currentTimeMillis();
    long windowStartTime = currentTime - convertToMillis(windowSize, timeUnit);
    // 獲取 Redisson 的 ZSet 操作對(duì)象
    RScoredSortedSet<Long> scoredSortedSet = redissonClient.getScoredSortedSet(key);

    // 1. 刪除窗口外的過(guò)期請(qǐng)求
    scoredSortedSet.removeRangeByScore(0, true, windowStartTime, true); // [0, windowStartTime]

    // 2. 添加當(dāng)前請(qǐng)求的時(shí)間戳到 ZSet
    scoredSortedSet.add(currentTime, currentTime); // score 和 value 均為時(shí)間戳

    // 3. 統(tǒng)計(jì)窗口內(nèi)請(qǐng)求數(shù)量
    int count = scoredSortedSet.size();
    return count > maxRequests;
}

private long convertToMillis(int windowSize, TimeUnit timeUnit) {
    return switch (timeUnit) {
        case SECONDS -> timeUnit.toMillis(windowSize);
        case MINUTES -> timeUnit.toMillis(windowSize);
        case HOURS -> timeUnit.toMillis(windowSize);
        case DAYS -> timeUnit.toMillis(windowSize);
        case MILLISECONDS -> windowSize;
        default -> throw new IllegalArgumentException("不支持的時(shí)間單位: " + timeUnit);
    };
}

@Aspect
@Component
@Order(Ordered.HIGHEST_PRECEDENCE + 20)
public class SlidingWindowLimitAspect {
    @Resource
    private RedissonClient redissonClient;
    private static final Logger log = LoggerFactory.getLogger(SlidingWindowLimitAspect.class);

    private static final String RATE_LIMIT_PREFIX = "rate_limit";

    @Around("@annotation(slidingWindowLimit)")
    public Object around(ProceedingJoinPoint joinPoint, SlidingWindowLimit slidingWindowLimit) throws Throwable {
        //獲取方法簽名
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        Method method = signature.getMethod();
        String methodName = method.getName();
        //判斷是否為Http請(qǐng)求
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        if(attributes == null){
            log.warn("方法 {} 不在 Web 請(qǐng)求上下文中，跳過(guò)限流檢查。", methodName);
            return joinPoint.proceed();
        }
        try {
            Object parseSpEL = parseSpEL(joinPoint, signature, slidingWindowLimit.keySpEL());
            String rateLimitKey = buildRateLimitKey(parseSpEL, slidingWindowLimit);
            if(isRateLimited(rateLimitKey, slidingWindowLimit.windowSize(), slidingWindowLimit.timeUnit(), slidingWindowLimit.maxRequests())){
                throw new RateLimitExceededException("Rate limit exceeded");
            }
            return joinPoint.proceed();
        }catch (RateLimitExceededException e){
            log.warn("方法 {} 觸發(fā)了限流，已拒絕訪問(wèn)。", methodName);
            throw e;
        }catch (Exception e){
            log.error("方法 {} 觸發(fā)了異常，已拒絕訪問(wèn)。", methodName, e);
            throw e;
        }
    }

    private Object parseSpEL(ProceedingJoinPoint joinPoint,MethodSignature signature, String keySpEL){
        StandardEvaluationContext context = new StandardEvaluationContext();

        Object[] args = joinPoint.getArgs();
        String[] parameterNames = signature.getParameterNames();

        for (int i = 0; i < args.length; i++) {
            if(parameterNames!=null && i< parameterNames.length){
                context.setVariable(parameterNames[i], args[i]);
            }else {
                context.setVariable("arg" + i, args[i]);
            }
        }

        ExpressionParser parser = new SpelExpressionParser();
        return parser.parseExpression(keySpEL).getValue(context);
    }

    private String buildRateLimitKey(Object keyValue, SlidingWindowLimit slidingWindowLimit){
        if(keyValue == null){
            throw new IllegalArgumentException("限流參數(shù)不能為空");
        }
        return String.format("%s:%s:%s",RATE_LIMIT_PREFIX,slidingWindowLimit.keySpEL(), keyValue);
    }

    private boolean isRateLimited(String key, int windowSize, TimeUnit timeUnit, int maxRequests){
        //獲取當(dāng)前時(shí)間數(shù)
        long currentTime = System.currentTimeMillis();
        long windowStartTime = currentTime - convertToMillis(windowSize, timeUnit);
        // 獲取 Redisson 的 ZSet 操作對(duì)象
        RScoredSortedSet<Long> scoredSortedSet = redissonClient.getScoredSortedSet(key);

        // 1. 刪除窗口外的過(guò)期請(qǐng)求
        scoredSortedSet.removeRangeByScore(0, true, windowStartTime, true); // [0, windowStartTime]

        // 2. 添加當(dāng)前請(qǐng)求的時(shí)間戳到 ZSet
        scoredSortedSet.add(currentTime, currentTime); // score 和 value 均為時(shí)間戳

        // 3. 統(tǒng)計(jì)窗口內(nèi)請(qǐng)求數(shù)量
        int count = scoredSortedSet.size();
        return count > maxRequests;
    }

    /**
     * 時(shí)間單位轉(zhuǎn)換，將時(shí)間單位轉(zhuǎn)換為毫秒數(shù)
     * @param windowSize 窗口大小
     * @param timeUnit 時(shí)間單位
     * @return
     */
    private long convertToMillis(int windowSize, TimeUnit timeUnit){
        return switch (timeUnit){
            case NANOSECONDS, SECONDS, MICROSECONDS, MINUTES, HOURS, DAYS -> timeUnit.toMillis(windowSize);
            case MILLISECONDS -> windowSize;
            default -> throw new IllegalArgumentException("不支持的時(shí)間單位: " + timeUnit);
        };
    }
}

@PostMapping("/send/code")
@SlidingWindowLimit(keySpEL = "#email.email",windowSize = 60, maxRequests = 3)
public Result sendVerificationCode(@RequestBody EmailSendDTO email) {
    userService.sendVerificationCode(email.getEmail());
    return Result.success();
}

{
    "code": 429,
    "message": "請(qǐng)求過(guò)于頻繁，請(qǐng)稍后再試",
    "data": null
}

private boolean isRateLimited(String key, int windowSize, TimeUnit timeUnit, int maxRequests){
    //獲取當(dāng)前時(shí)間數(shù)
    long currentTime = System.currentTimeMillis();
    long windowStartTime = currentTime - convertToMillis(windowSize, timeUnit);
    // 獲取 Redisson 的 ZSet 操作對(duì)象
    RScoredSortedSet<Long> scoredSortedSet = redissonClient.getScoredSortedSet(key);

    // 1. 刪除窗口外的過(guò)期請(qǐng)求
    scoredSortedSet.removeRangeByScore(0, true, windowStartTime, true); // [0, windowStartTime]

    // 2. 添加當(dāng)前請(qǐng)求的時(shí)間戳到 ZSet
    scoredSortedSet.add(currentTime, currentTime); // score 和 value 均為時(shí)間戳

    // 3. 統(tǒng)計(jì)窗口內(nèi)請(qǐng)求數(shù)量
    int count = scoredSortedSet.size();
    return count > maxRequests;
}

private boolean isRateLimited(String key, int windowSize, TimeUnit timeUnit, int maxRequests) {
    // 1. 計(jì)算窗口大?。ê撩耄?
    long windowMillis = convertToMillis(windowSize, timeUnit);
    // 2. 獲取當(dāng)前時(shí)間和窗口起始時(shí)間
    long currentTime = System.currentTimeMillis();
    long windowStartTime = currentTime - windowMillis;
    // 3. 生成唯一請(qǐng)求ID
    String requestId = UUID.randomUUID().toString();
    // 4. 計(jì)算過(guò)期時(shí)間（秒）
    long expireSeconds = calculateExpireSeconds(windowMillis);
    // 5. Lua腳本（使用分?jǐn)?shù)范圍精確統(tǒng)計(jì)）
    String luaScript =
            "redis.call('ZREMRANGEBYSCORE', KEYS[1], '-inf', ARGV[2])\n" +  // 清理過(guò)期數(shù)據(jù)
                    "local count = redis.call('ZCOUNT', KEYS[1], ARGV[2], ARGV[1])\n" +  // 精確統(tǒng)計(jì)窗口內(nèi)請(qǐng)求
                    "if count >= tonumber(ARGV[4]) then\n" +
                    "    return 1\n" +  // 觸發(fā)限流
                    "end\n" +
                    "redis.call('ZADD', KEYS[1], ARGV[1], ARGV[3])\n" +  // 添加當(dāng)前請(qǐng)求
                    "redis.call('EXPIRE', KEYS[1], ARGV[5])\n" +  // 設(shè)置過(guò)期時(shí)間
                    "return 0";  // 允許通過(guò)

    try {
        RScript script = redissonClient.getScript();
        Long result = script.eval(
                RScript.Mode.READ_WRITE,
                luaScript,
                RScript.ReturnType.INTEGER,
                Collections.singletonList(key),
                currentTime, windowStartTime, requestId, maxRequests, expireSeconds
        );
        return result != null && result == 1;
    } catch (Exception e) {
        log.error("限流服務(wù)異常，降級(jí)放行", e);
        return false; // Redis故障時(shí)允許請(qǐng)求
    }
}
private long calculateExpireSeconds(long windowMillis) {
    // 過(guò)期時(shí)間 = 2 * 窗口大小（秒），向上取整
    double expireSec = (windowMillis * 2.0) / 1000;
    long result = (long) Math.ceil(expireSec);
    return Math.max(1, result); // 至少1秒
}

127.0.0.1:6379> ZRANGE rate_limit:#email.email:6888@example.com 0 -1
1) "fbd525dd-0e1e-4abf-a578-8c1207e8f6f0"
127.0.0.1:6379> TTL rate_limit:#email.email:6888@example.com
(integer) 355
127.0.0.1:6379> ZRANGE rate_limit:#email.email:6888@example.com 0 -1
1) "fbd525dd-0e1e-4abf-a578-8c1207e8f6f0"
2) "a7c8d5c2-f4da-46ce-9f98-472ad702e1ad"
127.0.0.1:6379> TTL rate_limit:#email.email:6888@example.com
(integer) 355
127.0.0.1:6379> ZRANGE rate_limit:#email.email:6888@example.com 0 -1
1) "fbd525dd-0e1e-4abf-a578-8c1207e8f6f0"
2) "a7c8d5c2-f4da-46ce-9f98-472ad702e1ad"
3) "12ed502c-6225-45bd-b85e-1d3ed9e46ef6"
127.0.0.1:6379> TTL rate_limit:#email.email:6888@example.com
(integer) 355