EntityManager.merge() can insert new objects and update existing ones. Why would one want to use persist() (which can only create new objects)?

The JPA (Java Persistence API) specification has 2 different ways to specify entity composite keys: @IdClass and @EmbeddedId. I'm using both annotations on my mapped entities, but it turns out to...

I'm using the javax.persistence package to map my Java classes. I have entities like these: public class UserEntity extends IdEntity { } which extends a mapped superclass named IdEntity: @Map...

I have a book class with a list of authors: @Entity @Table(name = "book") public class Book extends Content { @ManyToMany(fetch = FetchType.LAZY) private List<Author> authors; ...} Now,...