When does the JPA set a @GeneratedValue @Id

Solution 1:

calling .persist() will not automatically set the id value. Your JPA provider will ensure that it is set before the entity is finally written to db. So you are right to assume that the id will be assigned when the transaction is committed. But this is not the only possible case. When you call .flush() the very same will happen.

Thomas

Update: Pay attention to Geek's comment, please. -> If GenerationType.Identity is used, the id will not be set by the provider before the entity is written to db. In this case id generation happens during the insert process on db level. Anyway, the JPA provider will ensure that the entity is updated afterwards and the generated id will be available in the @Id annotated property.

Solution 2:

AFAIK, the ID is only guaranteed to be assigned when the persistence context is flushed. It might be assigned sooner, but it depends on the generation strategy.