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| − | {{EclipseLink_UserGuide
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| − | |info=y
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| − | |toc=n
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| − | |eclipselink=y
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| − | |eclipselinktype=JPA
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| − | |api=y
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| − | |apis=
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| − | *[http://www.eclipse.org/eclipselink/api/latest/javax/persistence/Entity.html @Entity]
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| − | * [http://www.eclipse.org/eclipselink/api/latest/javax/persistence/IdClass.html @IdClass]
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| − | * [http://www.eclipse.org/eclipselink/api/latest/javax/persistence/Embedded.html @Embedded]
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| − | * [http://www.eclipse.org/eclipselink/api/latest/javax/persistence/GeneratedValue.html @GeneratedValue]
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| − | * [http://www.eclipse.org/eclipselink/api/latest/javax/persistence/TableGenerator.html @TableGenerator]
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| − | * [http://www.eclipse.org/eclipselink/api/latest/javax/persistence/SequenceGenerator.html @SequenceGenerator ]
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| − | * [http://www.eclipse.org/eclipselink/api/latest/javax/persistence/package-summary.html Package javax.persistence]}}
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| − | = Configuring Entities=
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| − | 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.
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| − | 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.
| + | '''[[Image:Elug_draft_icon.png|Warning]] See "Understanding Entities" in the [http://www.eclipse.org/eclipselink/documentation/ EclipseLink Concepts Guide]''' |
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| − | == Identifying an Entity ==
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| − | Use the <tt>@Entity</tt> annotation to specify that a class is an entity, as shown in the following example:
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| − | <source lang="java">
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| − | @Entity
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| − | public class Employee implements Serializable {
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| − | ... | + | |
| − | }
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| − | </source>
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| − | {{EclipseLink_Spec
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| − | |link=http://jcp.org/en/jsr/detail?id=220 | + | |
| − | |section=Chapter 2 "Entities"}}
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| − | ==Configuring an Entity's Persistent Identity==
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| − | Every entity must have a persistent identity, which is an equivalent of a primary key in a database table that stores the entity state.
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| − | By default, the EclipseLink persistence provider assumes that each entity has at least one field or property that serves as a primary key.
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| − | You can generate and/or configure the identity of your entities by using the following annotations:
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| − | | + | |
| − | *[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entities/Ids/Id|@Id]]
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| − | *[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entities/Ids/IdClass|@IdClass]]
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| − | *[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entities/Ids/EmbeddedId|@EmbeddedId]]
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| − | *[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entities/Ids/GeneratedValue|@GeneratedValue]]
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| − | *[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entities/Ids/TableGenerator|@TableGenerator]]
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| − | *[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entities/Ids/SequenceGenerator|@SequenceGenerator ]]
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| − | You can also use these annotations to fine-tune how your database maintains the identity of your entities.
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| − | <br>
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| − | <br>
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| − | {{EclipseLink_JPA
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| − | |previous=[[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Configuration/JPA/Overriding_and_Merging|Overriding and Merging Metadata Settings]]
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| − | |up=[[EclipseLink/UserGuide/JPA/Basic JPA Development|Basic JPA Development]]
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| − | |next=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entities/Ids/Id|@Id]]
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| − | |version=2.2.0 DRAFT}}
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See "Understanding Entities" in the EclipseLink Concepts Guide