@Component
public class RedisDBChangeUtil {
    @Autowired
    private StringRedisTemplate redisTemplate;

    public void setDataBase(int num) {
        LettuceConnectionFactory connectionFactory = (LettuceConnectionFactory) redisTemplate.getConnectionFactory();
        if (connectionFactory != null && num != connectionFactory.getDatabase()) {
            connectionFactory.setDatabase(num);
            connectionFactory.afterPropertiesSet();
            this.redisTemplate.setConnectionFactory(connectionFactory);
            connectionFactory.resetConnection();
        }
    }
}

redis单线程为什么那么快：

• 纯内存操作
• 使用IO多路复用技术
• 非CPU密集型任务

redis切换db