BloomFilter工具类

package com.zhao.sian.delta.config;

import java.util.Objects;

import com.google.common.hash.Funnel;
import com.google.common.hash.Hashing;

public class BloomFilter<T> {

	private int numHashFunctions;

	private int bitSize;

	private Funnel<T> funnel;

	public BloomFilter(Funnel<T> funnel, int expectedInsertions, double fpp) {
		if (Objects.isNull(funnel)) {
			throw new IllegalArgumentException("funnel cannot be empty");
		}
		bitSize = optimalNumOfBits(expectedInsertions, fpp);
		numHashFunctions = optimalNumOfHashFunctions(expectedInsertions, bitSize);
	}

	int[] murmurHashOffset(T value) {
		int[] offset = new int[numHashFunctions];

		long hash64 = Hashing.murmur3_128().hashObject(value, funnel).asLong();
		int hash1 = (int) hash64;
		int hash2 = (int) (hash64 >>> 32);
		for (int i = 1; i <= numHashFunctions; i++) {
			int nextHash = hash1 + i * hash2;
			if (nextHash < 0) {
				nextHash = ~nextHash;
			}
			offset[i - 1] = nextHash % bitSize;
		}

		return offset;
	}

	/**
	 * Calculate the length of the bit array
	 */
	private int optimalNumOfBits(long n, double p) {
		if (p == 0) {
			p = Double.MIN_VALUE;
		}
		return (int) (-n * Math.log(p) / (Math.log(2) * Math.log(2)));
	}

	/**
	 * Count the number of executions of the hash method
	 */
	private int optimalNumOfHashFunctions(long n, long m) {
		return Math.max(1, (int) Math.round((double) m / n * Math.log(2)));
	}

}

 

package com.zhao.sian.delta.config;

import java.util.Objects;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Service;

@Service
public class RedisService {

	@Autowired
	private RedisTemplate<String, ?> redisTemplate;

	/**
	 * Add value to bloom filter
	 */
	public <T> void addByBloomFilter(BloomFilter<T> bloomFilter, String key, T value) {
		if (Objects.isNull(bloomFilter)) {
			throw new IllegalArgumentException("bloomFilterHelper cannot be empty");
		}
		int[] offset = bloomFilter.murmurHashOffset(value);
		for (int i : offset) {
			redisTemplate.opsForValue().setBit(key, i, true);
		}
	}

	/**
	 * Determine whether the value exists in the bloom filter
	 */
	public <T> boolean existByBloomFilter(BloomFilter<T> bloomFilter, String key, T value) {
		if (Objects.isNull(bloomFilter)) {
			throw new IllegalArgumentException("bloomFilter cannot be empty");
		}
		int[] offset = bloomFilter.murmurHashOffset(value);
		for (int i : offset) {
			if (!redisTemplate.opsForValue().getBit(key, i)) {
				return false;
			}
		}
		return true;
	}

}

private BloomFilter<String> bloomFilter= new BloomFilter<>((Funnel<String>) (from, into) -> into.putString(from, Charsets.UTF_8)
        .putString(from, Charsets.UTF_8), 10000 , 0.01);