@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);
            this.redisTemplate.setConnectionFactory(connectionFactory);
            connectionFactory.resetConnection();
        }
    }
}

@RestController
@RequestMapping("/")
public class RedisStringController {
    
    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private RedisDBChangeUtil redisDBChangeUtil;

    @PostMapping("/changeDb")
    public String changeDb(){

       //默认的插入
        stringRedisTemplate.opsForValue().set("name","db0");

        //插入db1
        redisDBChangeUtil.setDataBase(1);
        stringRedisTemplate.opsForValue().set("name1","db1");

        //插入db2
        redisDBChangeUtil.setDataBase(2);
        stringRedisTemplate.opsForValue().set("name2","db2");

        return  "ok";
    }
}