2.4.1. Entity

You can fine tune some of the actions done by Hibernate on entities beyond what the EJB3 spec offers.

@org.hibernate.annotations.Entity adds additional metadata that may be needed beyond what is defined in the standard @Entity

mutable: whether this entity is mutable or not
dynamicInsert: allow dynamic SQL for inserts
dynamicUpdate: allow dynamic SQL for updates
selectBeforeUpdate: Specifies that Hibernate should never perform an SQL UPDATE unless it is certain that an object is actually modified.
polymorphism: whether the entity polymorphism is of PolymorphismType.IMPLICIT (default) or PolymorphismType.EXPLICIT
persister: allow the overriding of the default persister implementation
optimisticLock: optimistic locking strategy (OptimisticLockType.VERSION, OptimisticLockType.NONE, OptimisticLockType.DIRTY or OptimisticLockType.ALL)

Note

@javax.persistence.Entity is still mandatory, @org.hibernate.annotations.Entity is not a replacement.

Here are some additional Hibernate annotation extensions

@org.hibernate.annotations.BatchSize allows you to define the batch size when fetching instances of this entity ( eg. @BatchSize(size=4) ). When loading a given entity, Hibernate will then load all the uninitialized entities of the same type in the persistence context up to the batch size.

@org.hibernate.annotations.Proxy defines the laziness attributes of the entity. lazy (default to true) define whether the class is lazy or not. proxyClassName is the interface used to generate the proxy (default is the class itself).

@org.hibernate.annotations.Where defines an optional SQL WHERE clause used when instances of this class is retrieved.

@org.hibernate.annotations.Check defines an optional check constraints defined in the DDL statetement.

@OnDelete(action=OnDeleteAction.CASCADE) on joined subclasses: use a SQL cascade delete on deletion instead of the regular Hibernate mechanism.

@Table(appliesTo="tableName", indexes = { @Index(name="index1", columnNames={"column1", "column2"} ) } ) creates the defined indexes on the columns of table tableName. This can be applied on the primary table or any secondary table. The @Tables annotation allows your to apply indexes on different tables. This annotation is expected where @javax.persistence.Table or @javax.persistence.SecondaryTable(s) occurs.

Note

@org.hibernate.annotations.Table is a complement, not a replacement to @javax.persistence.Table. Especially, if you want to change the default name of a table, you must use @javax.persistence.Table, not @org.hibernate.annotations.Table.

@Entity
@BatchSize(size=5)
@org.hibernate.annotations.Entity(
        selectBeforeUpdate = true,
        dynamicInsert = true, dynamicUpdate = true,
        optimisticLock = OptimisticLockType.ALL,
        polymorphism = PolymorphismType.EXPLICIT)
@Where(clause="1=1")
@org.hibernate.annotations.Table(name="Forest", indexes = { @Index(name="idx",
columnNames = { "name", "length" } ) } )
public class Forest { ... }

@Entity
@Inheritance(
    strategy=InheritanceType.JOINED
)
public class Vegetable { ... }

@Entity
@OnDelete(action=OnDeleteAction.CASCADE)
public class Carrot extends Vegetable { ... }