Re: circular references and ORM

Daniel Pitts <>
Wed, 07 May 2008 16:13:13 -0700
Mark Thornton wrote:

Rex Mottram wrote:

I know that "premature optimization is the root of all evil" but OTOH
there are situations where you want to think about future needs before
putting hands to keyboard .... I'm building a web app which currently
has no persist store. There is, however, a plan to retrofit a
persistence framework of the JPA/Hibernate sort eventually, and I'm
wondering if circular object references are going to be a problem when
that time comes.

In other words I've got code now where a Barrel contains a collection
of Monkeys, and each Monkey contains a reference back to its
containing Barrel, so that the Barrel class can have (say) a
getMonkeyIterator() method and the Monkey class can have a getBarrel().

This is absolutely normal and works fine with JPA.

Mark Thornton

In particular for JPA and Hibernate using annotations, you have a
@OneToMany(targetEntity=Monkey.class) Set<Monkey> monkeys; in the
Barrel, and a @ManyToOne Barrel barrel; in the Monkey class.

What's important to remember in Relational theory is that ALL relations
include two endpoints, whether you model that explicitly or not.
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