java接口限流如何实现

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在 Java 中实现接口限流可以使用以下几种方式：

计数器：维护一个计数器来统计每个接口的请求数量，当请求数量超过设定的阈值时，拒绝后续的请求。这可以使用并发容器如 ConcurrentHashMap 来实现，其中接口作为 key，计数器作为 value。

import java.util.concurrent.ConcurrentHashMap;

public class RateLimiter {private static ConcurrentHashMap<String, Integer> counters = new ConcurrentHashMap<>();
    private static final int MAX_REQUESTS = 100; // 设定的阈值 

    public static boolean allowRequest(String interfaceName) {counters.putIfAbsent(interfaceName, 0);
        int count = counters.get(interfaceName);
        if (count >= MAX_REQUESTS) {return false;
        }
        counters.put(interfaceName, count + 1);
        return true;
    }

    public static void main(String[] args) {String interfaceName = "interface1";
        for (int i = 0; i < 110; i++) {if (allowRequest(interfaceName)) {System.out.println("Allow request for interface: " + interfaceName);
            } else {System.out.println("Reject request for interface: " + interfaceName);
            }
        }
    }
}

滑动窗口：使用一个固定长度的时间窗口，统计窗口内的请求数量。当请求数量超过设定的阈值时，拒绝后续的请求。这可以使用队列或数组来保存请求的时间戳，并通过计算窗口内的请求数量来进行限流。

import java.util.ArrayDeque;
import java.util.Queue;

public class RateLimiter {private static Queue<Long> timestamps = new ArrayDeque<>();
    private static final int WINDOW_SIZE = 1000; // 窗口大小，单位为毫秒 
    private static final int MAX_REQUESTS = 100; // 设定的阈值 

    public static boolean allowRequest() {long now = System.currentTimeMillis();
        timestamps.offer(now);
        while (!timestamps.isEmpty() && now - timestamps.peek() > WINDOW_SIZE) {timestamps.poll();
        }
        return timestamps.size() <= MAX_REQUESTS;}

    public static void main(String[] args) {for (int i = 0; i < 110; i++) {if (allowRequest()) {System.out.println("Allow request");
            } else {System.out.println("Reject request");
            }
            try {Thread.sleep(100);
            } catch (InterruptedException e) {e.printStackTrace();
            }
        }
    }
}

令牌桶：使用一个固定速率产生令牌，每个请求需要获取一个令牌才能通过。当令牌数量不足时，拒绝后续的请求。这可以使用 ScheduledExecutorService 来定时产生令牌，并使用 Semaphore 来控制令牌的获取。

import java.util.concurrent.Semaphore;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class RateLimiter {private static Semaphore tokens = new Semaphore(10); // 初始令牌数量 
    private static final int RATE = 1; // 产生令牌的速率，单位为个 / 秒 

    public static boolean allowRequest() {return tokens.tryAcquire();}

    public static void main(String[] args) {ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1);
        executor.scheduleAtFixedRate(() -> {int availableTokens = tokens.availablePermits();
            if (availableTokens < RATE) {tokens.release(RATE - availableTokens);
            }
        }, 0, 1, TimeUnit.SECONDS);

        for (int i = 0; i < 20; i++) {if (allowRequest()) {System.out.println("Allow request");
            } else {System.out.println("Reject request");
            }
            try {Thread.sleep(100);
            } catch (InterruptedException e) {e.printStackTrace();
            }
        }

        executor.shutdown();}
}