JPA Annotations for Relationships

Relationships are persistent fields in persistable classes that reference other entity objects. The four relationship modes are represented by the following annotations:

• javax.persistence.ManyToMany
• javax.persistence.ManyToOne
• javax.persistence.OneToMany
• javax.persistence.OneToOne

Unlike ORM JPA implementations, ObjectDB does not enforce specifying any of the annotations above. Specifying a relationship annotation enables configuring cascade and fetch policy, using the following enum types:

• javax.persistence.CascadeType
• javax.persistence.FetchType

Additional annotations are supported by ObjectDB for the inverse side of a bidirectional relationship (which is calculated by a query) :

• javax.persistence.OrderBy
• javax.persistence.MapKey

Details about all these annotations are provided in Chapter 2 of the ObjectDB manual.