ByThorben JanssenA lot of applications use primary keys that are based on a sequence but use an additional prefix that contains semantic information. Here are some typical examples: A fixed String as a prefix followed by a sequence-based value of fixed or variable length, e.g., B_00001 or B_1 Year and month as a prefix followed by…
ByThorben JanssenLike all object-oriented programing languages, Java supports the fundamental concepts of inheritance and composition. There is an important difference between both concepts. Inheritance enables you to model an is-a association between two classes by extending a superclass. Composition models a has-a association by referencing another class in an instance variable. You can use both concepts…
ByThorben JanssenWhen you model your database, you will most likely define several many-to-one or one-to-many associations. And it’s, of course, the same when you model your entities. It’s quite easy to do that with JPA and Hibernate. You just need an attribute that represents the association and annotate it with a @ManyToOne or @OneToMany association. But…
ByThorben JanssenThe CascadeTypes REMOVE and ALL, which includes REMOVE, provide a comfortable option to remove an entity together with all its child entities. But it creates several issues for to-many associations, and you should only use it for to-one relationships.
ByThorben JanssenJPA 2.2 was only a small release, and I think that’s ok. JPA 2.1 already provides a good enough toolset for most applications. But there was nevertheless some work to do.