How To Define A Composite Primary Key Via @IdClass
Description: This application is a proof of concept of how to define a composite key via @IdClass. This application uses two entities, Author and Book involved in a lazy bidirectional @OneToMany association. The identifier of Author is composed by name and age via AuthorId class. The identifier of Book is just a typical auto-generated numeric value.
Key points:
- the composite key class (e.g.,
AuthorId) ispublic - the composite key class must implement
Serializable - the composite key must define
equals()andhashCode() - the composite key must define a no-arguments constructor
Note: The @IdClass can be useful when we cannot modify the compsite key class. Otherwise, rely on @Embeddable.
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