SpringBoot 使用 BloomFilter（布隆过滤器）

使用BloomFilter（布隆过滤器）可解决缓存穿透问题

1.导入依赖

	org.redisson
	redisson

2.配置redisson

@Configuration
public class RedissonConfig {

    //从application.properties中获取spring.redis.host配置
    @Value("${spring.redis.host}")
    private String redisHost;
    //从application.properties中获取spring.redis.port配置
    @Value("${spring.redis.port}")
    private int redisPort;
    //从application.properties中获取bloomfilter.v1参数
    @Value("${bloomfilter.v1}")
    private Long v1;
    //从application.properties中获取bloomfilter.var3容错率参数
    @Value("${bloomfilter.var3}")
    private double var3;

    //将redissonClient配置为springBean后可以重新根据自己需要配置loomFilter
    @Bean
    public RedissonClient redissonClient(){
        Config config = new Config();
        config.useSingleServer().setAddress("redis://"+redisHost+":"+redisPort);
        return Redisson.create(config);
    }

    //配置默认的loomFilter
    @Bean
    public RBloomFilter bloomFilter(){
        RBloomFilter bloomFilter=redissonClient().getBloomFilter("bloom-filter");
        bloomFilter.tryInit(v1,var3);
        return bloomFilter;
    }
}

3.初始化bloomfilter内容

@Component
public class StartUser implements ApplicationRunner{

	@Autowired
	private UserMapper userMapper;
	@Autowired
	private RedissonConfig redissonConfig;

    private RBloomFilter rbloomFilter;

    @PostConstruct
    public void init(){
        rbloomFilter = redissonConfig.bloomFilter();
    }

	@Override
	public void run(ApplicationArguments args) {
		List users = userMapper.selectList();
		value.stream().map(User->{
			rbloomFilter.add(User.getUserId());
            return null;
		}).collect(Collectors.toList());	
	}
}

4.使用，判断是否存在，不存在不让查询数据库

@Service
public class UserServiceImpl implements UserService{

	@Autowired
	private UserMapper userMapper;
	@Autowired
	private RedissonConfig redissonConfig;

    private RBloomFilter rbloomFilter;

    @PostConstruct
    public void init(){
        rbloomFilter = redissonConfig.bloomFilter();
    }

	public ApiRes getUserById(String userId){
		//布隆过滤器拦截
		boolean contains = rbloomFilter.contains(userId);
		if (!contains){
		    return ApiRes.fail(407,"userId不存在！");
		}
		
		User user=userMapper.getUserById(userId);
		return ApiRes.success(user);
	}
}