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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Entities/Creating and Configuring Entities"

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Revision as of 12:33, 19 April 2011

EclipseLink JPA


Configuring Entities

An entity is a lightweight persistence domain object. Typically, an entity represents a table in a relational database, and each entity instance corresponds to a row in the table. The primary programming artifact of an entity is the entity class, although entities can use helper classes.

The persistent state of an entity is represented either through persistent fields or persistent properties. These fields or properties use object/relational mapping annotations to map the entities and entity relationships to the relational data in the underlying data store.

Identifying an Entity

Use the @Entity annotation to specify that a class is an entity, as shown in the following example:

@Entity
public class Employee implements Serializable {
...
}
Elug javaspec icon.gif

For more information, see Chapter 2 "Entities" in the JPA Specification.

Configuring an Entity's Persistent Identity

Every entity must have a persistent identity, which is an equivalent of a primary key in a database table that stores the entity state.

By default, the EclipseLink persistence provider assumes that each entity has at least one field or property that serves as a primary key.

You can generate and/or configure the identity of your entities by using the following annotations:

You can also use these annotations to fine-tune how your database maintains the identity of your entities.



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Version: 2.2.0 DRAFT
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