基于Redis和Bucket4j的Java分布式限流器：实现滚动窗口与回退机制

<dependencies>     <!-- Bucket4j Core -->     <dependency>         <groupId>com.github.vladimir-bukhtoyarov</groupId>         <artifactId>bucket4j-core</artifactId>         <version>8.1.1</version> <!-- 请使用最新稳定版本 -->     </dependency>     <!-- Bucket4j Jedis integration -->     <dependency>         <groupId>com.github.vladimir-bukhtoyarov</groupId>         <artifactId>bucket4j-redis</artifactId>         <version>8.1.1</version> <!-- 确保与bucket4j-core版本一致 -->     </dependency>     <!-- Jedis client -->     <dependency>         <groupId>redis.clients</groupId>         <artifactId>jedis</artifactId>         <version>4.3.1</version> <!-- 请使用最新稳定版本 -->     </dependency> </dependencies>

import io.github.bucket4j.Bandwidth; import io.github.bucket4j.Bucket; import io.github.bucket4j.Bucket4j; import io.github.bucket4j.ConsumptionProbe; import io.github.bucket4j.redis.jedis.JedisBasedProxyManager; import redis.clients.jedis.JedisPool; import redis.clients.jedis.JedisPoolConfig;  import java.time.Duration; import java.util.concurrent.TimeUnit; import java.util.function.Supplier;  public class DistributedRateLimiter {      private static JedisPool jedisPool;     private static JedisBasedProxyManager proxyManager;      public static void initRedis(String redisHost, int redisPort) {         JedisPoolConfig poolConfig = new JedisPoolConfig();         poolConfig.setMaxTotal(10); // 最大连接数         poolConfig.setMaxIdle(5);   // 最大空闲连接数         jedisPool = new JedisPool(poolConfig, redisHost, redisPort);         proxyManager = new JedisBasedProxyManager(jedisPool);     }      /**      * 获取或创建限流桶。      * 每个唯一的key对应一个独立的限流桶。      *      * @param key 限流的唯一标识符（例如：用户ID, IP地址, API路径）      * @param capacity 令牌桶容量      * @param refillTokens 每次填充的令牌数      * @param refillPeriod 令牌填充周期      * @return 配置好的限流桶      */     public static Bucket getOrCreateLimiterBucket(String key, long capacity, long refillTokens, Duration refillPeriod) {         // 定义限流带宽         Bandwidth limit = Bandwidth.builder()                 .capacity(capacity) // 令牌桶容量                 .refillGreedy(refillTokens, refillPeriod) // 令牌填充策略：每 refillPeriod 填充 refillTokens 个令牌                 .build();          // 使用proxyManager获取或创建分布式桶         // key是限流器的唯一标识，Supplier是当key不存在时如何创建桶的定义         return Bucket4j.builder()                 .addLimit(limit)                 .build(proxyManager, key);     }      public static void main(String[] args) throws InterruptedException {         // 初始化Redis连接池         initRedis("localhost", 6379); // 假设Redis运行在本地默认端口          String userId = "user:123";         // 为该用户设置限流：每秒10个请求，最大突发20个请求         Bucket userBucket = getOrCreateLimiterBucket(userId, 20, 10, Duration.ofSeconds(1));          System.out.println("--- 模拟用户请求 ---");         for (int i = 0; i < 30; i++) {             // 尝试消费一个令牌             ConsumptionProbe probe = userBucket.tryConsumeAndReturnRemaining(1);              if (probe.isConsumed()) {                 // 请求成功                 System.out.printf("请求 %d 成功！剩余令牌：%d%n", i + 1, probe.getRemainingTokens());             } else {                 // 请求被拒绝                 long nanosToWaitForRefill = probe.getNanosToWaitForRefill();                 long millisToWaitForRefill = TimeUnit.NANOSECONDS.toMillis(nanosToWaitForRefill);                 System.err.printf("请求 %d 被拒绝！需要等待 %d 毫秒后重试。当前剩余令牌：%d%n",                         i + 1, millisToWaitForRefill, probe.getRemainingTokens());                  // 模拟客户端等待回退时间                 if (millisToWaitForRefill > 0) {                     Thread.sleep(millisToWaitForRefill);                 }             }             // 每次请求间隔模拟             Thread.sleep(50);         }          // 关闭Redis连接池         jedisPool.close();     } }