春天的验证者应该访问数据库吗？

I'm not really sure if it's a good design decision to make the validators validate commands based on the state of the database. For example if I need to validate a User bean besides checking if the email and username are empty etc. I also need to reject values if they are already used. Should this kind of logic go in the validators or the service objects?I'm not really sure if it's a good design decis