Mapping Relationships with Hibernate

How to Program with Java Podcast

In the past we have learned about database relationships, specifically the One-to-Many as well as the Many-to-Many and One-to-One and that was all good, great and grand…

But now I want to talk about how to create those same relationships inside of Hibernate.

Specifically, I want to focus on the One-to-Many relationship in Hibernate and how we go about mapping it out in our Java objects.

But before we do, a word on unidirectional and bidirectional relationships.

Unidirectional vs Bidirectional

In Hibernate, it’s possible to map all three relationships that are available in a standard database, these include:

• One-to-One
• One-to-Many
• Many-to-Many

But what Hibernate also includes is the ability to make EACH of those relationships either unidirectional or bidirectional.

This means that we can have a unidirectional One-to-One and a bidirectional One-to-One mapping, as well as a unidirectional One-to-Many and a bidirectional One-to-Many, as well as a unidirectional Many-to-Many and a bidirectional Many-to-Many relationship.

That’s a lot of relationships!

So what exactly are unidirectional and bidirectional relationships?

Learn more on the show notes page via http://howtoprogramwithjava.com/session53