How to persist every new entity?

Question

I expect every instantiated entity to correspond to a tuple (& co) in the database. In the examples I see around, one always instantiates the entity (via a constructor) and then calls persist with that entity. I find this error-prone, and was wondering if it wasn't possible to have every instantiated entity automatically managed/persisted/reflected to the database (at least intended to).

This also seems to prevent me from persisting instance variable entities. I.e. I've an entity which instantiates another (entities it has an association with) in its constructor.

Answer 1

That's just a practice. The model shouldn't be aware of any DAO/persistence logic. If it does, then it is tight coupled and not reuseable for another persistence frameworks. However, if you are sure that you stick to JPA for ages, then you may consider to do so. But this is generally just not a good practice. The model may not be reuseable in another layers then. For example, you may want create a mock/dummy model object for the view layer to let a new user fill in the registration details and then only persist it when submission and validation is done succesfully.