Redis缓存：高性能数据存储

概述

Redis是一个开源的内存数据库，它支持多种数据结构，具有高性能、高可用的特点，广泛应用于缓存、会话管理、消息队列等场景。

1. Redis数据结构

@Component
public class RedisDataStructure {
    private final StringRedisTemplate redisTemplate;

    public void stringDemo() {
        redisTemplate.opsForValue().set("name", "John");
        String name = redisTemplate.opsForValue().get("name");
    }

    public void hashDemo() {
        Map<String, String> map = new HashMap<>();
        map.put("name", "John");
        map.put("age", "25");
        redisTemplate.opsForHash().putAll("user:1", map);
    }

    public void listDemo() {
        redisTemplate.opsForList().leftPush("queue", "task1");
        String task = redisTemplate.opsForList().leftPop("queue");
    }

    public void setDemo() {
        redisTemplate.opsForSet().add("tags", "java", "spring", "redis");
        Set<String> tags = redisTemplate.opsForSet().members("tags");
    }

    public void zSetDemo() {
        redisTemplate.opsForZSet().add("leaderboard", "player1", 100);
        Set<String> topPlayers = redisTemplate.opsForZSet()
            .reverseRange("leaderboard", 0, 9);
    }
}

2. Spring Boot + Redis

import org.springframework.cache.annotation.Cacheable;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.CacheEvict;

@Service
public class UserService {
    @Cacheable(value = "users", key = "#id")
    public User findById(Long id) {
        return userRepository.findById(id).orElse(null);
    }

    @CachePut(value = "users", key = "#user.id")
    public User update(User user) {
        return userRepository.save(user);
    }

    @CacheEvict(value = "users", key = "#id")
    public void delete(Long id) {
        userRepository.deleteById(id);
    }
}

3. 缓存策略

@Service
public class CacheStrategy {
    private final StringRedisTemplate redisTemplate;

    // 缓存穿透：查询不存在的数据 -> 缓存空值
    public User getUserWithNullCache(Long id) {
        String cacheKey = "user:" + id;
        String cached = redisTemplate.opsForValue().get(cacheKey);
        if ("NULL".equals(cached)) return null;
        if (cached != null) return JSON.parseObject(cached, User.class);

        User user = userRepository.findById(id).orElse(null);
        if (user == null) {
            redisTemplate.opsForValue().set(cacheKey, "NULL", 5, TimeUnit.MINUTES);
        } else {
            redisTemplate.opsForValue().set(cacheKey, JSON.toJSONString(user), 30, TimeUnit.MINUTES);
        }
        return user;
    }
}

4. 分布式锁

@Service
public class DistributedLock {
    private final StringRedisTemplate redisTemplate;

    public boolean tryLock(String lockKey, long timeout) {
        return redisTemplate.opsForValue()
            .setIfAbsent(lockKey, "1", timeout, TimeUnit.SECONDS);
    }

    public void unlock(String lockKey) {
        redisTemplate.delete(lockKey);
    }
}

最佳实践

1. 选择合适的数据结构：根据场景选择String/Hash/List/Set/ZSet
2. 设置过期时间：避免内存溢出
3. 缓存策略：根据场景选择合适的缓存策略
4. 分布式锁：使用Redis实现分布式锁
5. 监控Redis：使用Redis监控工具

总结

Redis是一款高性能的内存数据库，掌握Redis的数据结构和使用方式，可以实现高性能的缓存方案。