Object Relational Mappers

Java: Hibernate

• If you specify a many-to-one or one-to-many mapping, be sure to use the same mapping as the Java collection interface. A Set mapping won't work with a List collection, for example.

• In Hibernate, lazy loading is on by default for collections. This means the collections are fetched from the database only when they are used (never if they are not used). Warning: if the loading appears when the Hibernate session is already closed, it will 'fail.