布隆过滤器检测元素是否存在的示例

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * 布隆过滤器 -> redis -> mysql
 * @autor java265.com
 * @date 2024-01-18
 */
@Service
public class StudentServiceImpl implements StudentService {
    public static final String CACHE_KEY = "student:";

    @Autowired
    private StudentMapper studentMapper;

    @Autowired
    private redisTemplate redisTemplate;

    public void addstudent(student student){
        int i = studentMapper.insertSelective(student);

        if(i > 0) {
            //到数据库里面，重新捞出新数据出来，做缓存
            student=studentMapper.selectByPrimaryKey(student.getId());
            //缓存key
            String key=CACHE_KEY+student.getId();
            //往mysql里面插入成功随后再从mysql查询出来，再插入redis
            redisTemplate.opsForValue().set(key,student);
        }
    }

    public student findstudentById(Integer studentId){
        student student = null;

        //缓存key的名称
        String key=CACHE_KEY+studentId;

        // 查询redis
        student = (student) redisTemplate.opsForValue().get(key);

        //redis没有，查询mysql
        if(student==null) {
            student=studentMapper.selectByPrimaryKey(studentId);
            // mysql有，redis没有
            if (student != null) {
                // 把mysql捞到的数据写入redis
                redisTemplate.opsForValue().set(key,student);
            }
        }
        return student;
    }

    /**
     * BloomFilter -> redis -> mysql
     * 白名单：whites
     */
    public student findStudentByIdWithBloomFilter (Integer studentId) {
        student student = null;

        String key = CACHE_KEY + studentId;

        //布隆过滤器校验，无是绝对无，有是可能有
        if(!checkWithBloomFilter("whites",key)) {
            log.info("白名单无此顾客信息:{}",key);
            return null;
        }

        //查询redis
        student = (Student) redisTemplate.opsForValue().get(key);
        //redis没有，查询mysql
        if (student == null) {
            student = studentMapper.selectByPrimaryKey(studentId);
            // mysql有，redis没有
            if (student != null) {
                // 把mysql捞到的数据写入redis
                redisTemplate.opsForValue().set(key, student);
            }
        }
        return student;
    }

    /**
     * 查询布隆过滤器中是否存在
     */
    public boolean checkWithBloomFilter(String checkItem,String key) {
        int hashValue = Math.abs(key.hashCode());
        long index = (long) (hashValue % Math.pow(2, 32));
        return redisTemplate.opsForValue().getBit(checkItem, index);
    }
}