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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Entities/Ids/Id"
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The <tt>@Id</tt> annotation does not have attributes. | The <tt>@Id</tt> annotation does not have attributes. | ||
| − | By default, EclipseLink persistence provider chooses the most appropriate primary key generator (see [[ | + | By default, EclipseLink persistence provider chooses the most appropriate primary key generator (see [[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entity/GeneratedValue|@GeneratedValue]]) and is responsible for managing primary key values: you do not need to take any further action if you are satisfied with the persistence provider's default key generation mechanism. |
This example shows how to use this annotation to designate the persistent field <tt>empID</tt> as the primary key of the <tt>Employee</tt> table. | This example shows how to use this annotation to designate the persistent field <tt>empID</tt> as the primary key of the <tt>Employee</tt> table. | ||
| − | <span id=" | + | <span id="Example_Usage_of_@Id_Annotation"></span> |
''''' Usage of @Id Annotation''''' | ''''' Usage of @Id Annotation''''' | ||
<source lang="java"> | <source lang="java"> | ||
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</source> | </source> | ||
| − | The <tt>@Id</tt> annotation supports the use of EclipseLink converters (see [[ | + | The <tt>@Id</tt> annotation supports the use of EclipseLink converters (see [[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Basic_Mappings/Default_Conversions_and_Converters|Using EclipseLink JPA Converters]]). |
| − | + | {{EclipseLink_Spec | |
| + | |link=http://jcp.org/en/jsr/detail?id=220 | ||
| + | |section=Section 9.1.8 "Id Annotation"}} | ||
Revision as of 13:04, 16 June 2010
@Id
Use the @Id annotation to designate one or more persistent fields or properties as the entity's primary key.
For each entity, you must designate at least one of the following:
- one @Id
- one @EmbeddedId
- multiple @Id and an @IdClass
Note: The last option in the preceding list – @Id and @IdClass combination – is applicable to composite primary key configuration.
The @Id annotation does not have attributes.
By default, EclipseLink persistence provider chooses the most appropriate primary key generator (see @GeneratedValue) and is responsible for managing primary key values: you do not need to take any further action if you are satisfied with the persistence provider's default key generation mechanism.
This example shows how to use this annotation to designate the persistent field empID as the primary key of the Employee table.
Usage of @Id Annotation
@Entity public class Employee implements Serializable { @Id private int empID; ... }
The @Id annotation supports the use of EclipseLink converters (see Using EclipseLink JPA Converters).
For more information, see Section 9.1.8 "Id Annotation" in the JPA Specification.
