EclipseLink/Examples/JPA/Migration/Hibernate/V3Annotations

This example catalogs the migration from Hibernate(TM) Annotations to EclipseLink JPA with its custom annotations. This is a work in progress so please feel free to add your comments or additional content. If you are trying to migrate from a Hibernate annotation that is not covered here please post a question to the EclipseLink newsgroup.

Entity Annotations

These annotations are configured on the entity class.

@org.hibernate.annotations.Entity

@org.hibernate.annotations.Entity(
		selectBeforeUpdate = true,
		dynamicInsert = true, dynamicUpdate = true,
		optimisticLock = OptimisticLockType.ALL,
		polymorphism = PolymorphismType.EXPLICIT)

Dynamic Insert/Update

By default EclipseLink will always insert all mapped columns and will only update the columns that have changed. If alternate operations are required then the queries used for these operations can be customized using API, SQL, or Stored Procedures.

Optimistic Locking

EclipseLink's optimistic locking functionality supports all of the Hibernate locking types and more. This table translated the locking types from Hibernate's @Entity(optimisticLock) attributes into the EclipseLink locking policies which can be configured with @OptimisticLocking or in EclipseLink's ORM.XML.

Hibernate's OptimisticLockType	Description	EclipseLink OptimisticLocking
NONE	no optimistic locking	EclipseLink defaults to no optimistic locking
VERSION	use a column version	JPA @Version or EclipseLink @OptimisticLocking(type = OptimisticLockingType.VERSION_COLUMN)
DIRTY	dirty columns are compared	JPA @Version or EclipseLink @OptimisticLocking(type = OptimisticLockingType.CHANGED_COLUMNS)
ALL	all columns are compared	@OptimisticLocking(type = OptimisticLockingType.ALL_COLUMNS)

Additionally EclipseLink provides support for comparing a specific set of selected columns using OptimisticLockingType.SELECTED_COLUMNS. This approach allows you to select the critical columns that should be compared if the CHANGED or ALL strategies do not meet your needs.

Custom Sequence Generator

In Hibernate a custom generator for sequence values can be defined and used as:

   @Id
   @GeneratedValue(generator = "system-uuid")
   @GenericGenerator(name = "system-uuid", strategy = "mypackage.UUIDGenerator")
   public String getTransactionGuid()

With EclipseLink a custom sequence generator can be implemented and registered for use using the @GeneratedValue. See: How to use Custom Sequencing (ie. UUID) for more details.