CODEWITHSUNDEEP
javajpajpa-2.0
Alexey Romanov
Alexey Romanov

Reputation: 170735

JPA 2 inherited @Id property

Especially when working with JPA v1.0, try not to use id inheritance.

What is the difference with JPA 2? In particular, does it work better, i.e., can a Stapler and a Chair in the example have the same id when strategy=GenerationType.IDENTITY is used? Or does it depend on JPA implementation and/or database driver?

Upvotes: 0

Views: 136

Answers (1)

James
James

Reputation: 18379

I don't think that blog post makes a whole lot of sense.

I'm not even sure it is possible to not defined the Id in a superclass, unless it is a @MappedSuperclass.

It seems to be worried about running out of Ids. If you could run out of Ids with n subclasses, then you will also run out with one class, just take you n times as much time, which is not much longer. But running out of ids is not a problem as long as you use a long not and int.

A int id will last you about 100 years at one insert per second. Still not "soon", but for higher throughputs possible to run out.

A long will last you about 300 million years at one per millisecond. Not very "soon".

See, http://en.wikibooks.org/wiki/Java_Persistence/Identity_and_Sequencing#Running_Out_of_Numbers

Upvotes: 2

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