Composite primary keys are denoted using the The direction of a relationship can be either bidirectional or unidirectional.
A bidirectional relationship has both an owning side and an inverse side.
For example, if it has a persistent property that contains a set of phone numbers, the value is an entity and part of a many-to-many or one-to-many unidirectional relationship, it will be mapped as a join table in the underlying database.
Each constraint is associated with at least one validator class that validates the value of the constrained field or property.
For every persistent property property of type Type of the entity, there is a getter method .
Collection-valued persistent fields and properties must use the supported Java collection interfaces regardless of whether the entity uses persistent fields or properties.
If the entity uses persistent properties, the entity must follow the method conventions of Java Beans components.
Java Beans-style properties use getter and setter methods that are typically named after the entity class’s instance variable names.
The following collection interfaces may be used: If the entity class uses persistent fields, the type in the preceding method signatures must be one of these collection types.