API 接口AOP、Redis限流【固定窗口、滑动窗口、漏桶、令牌桶】

在实现API接口的AOP（面向切面编程）和使用Redis进行限流时，可以使用Spring Boot框架结合Spring Data Redis和AspectJ来实现。以下是使用固定窗口和滑动窗口两种算法的示例代码：

1. 引入依赖（Maven示例）：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjweaver</artifactId>
</dependency>

2. 配置Redis：

@Configuration
public class RedisConfig {
    @Bean
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate<String, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }
}

3. 实现限流的AOP切面：

@Aspect
@Component
public class RateLimitAspect {
 
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;
 
    @Before("@annotation(rateLimit)")
    public void rateLimit(JoinPoint joinPoint, RateLimit rateLimit) {
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        Method method = signature.getMethod();
        String key = method.getAnnotation(RateLimit.class).key();
        int limit = method.getAnnotation(RateLimit.class).limit();
        long windowSize = method.getAnnotation(RateLimit.class).windowSize();
 
        long now = System.currentTimeMillis();
        List<Long> timestamps = redisTemplate.opsForList().range(key, 0, -1);
        if (timestamps == null) {
            timestamps = new ArrayList<>();
        }
 
        // 固定窗口限流
        if (windowSize > 0) {
            while (timestamps.size() > 0 && now - timestamps.get(0) > windowSize) {
                timestamps.remove(0);
            }
            if (timestamps.size() >= limit) {
                throw new RuntimeException("Rate limit exceeded");
            }
        }
 
        // 滑动窗口限流
        if (timestamps.size() >= limit) {
            throw new RuntimeException("Rate limit exceeded");
        }
 
        timestamps.add(now);
        redisTemplate.opsForList().trim(key, 0, limit - 1);
        redisTemplate.opsForList().rightPush(key, now);
    }
}

4. 定义注解RateLimit：

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface RateLimit {