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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Entities/Ids/SequenceGenerator"
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If you use the [[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entity/GeneratedValue|@GeneratedValue annotation]] to specify a primary key generator of type <tt>SEQUENCE</tt>, then you can use the <tt>@SequenceGenerator</tt> annotation to fine-tune this primary key generator to do the following: | If you use the [[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Entity/GeneratedValue|@GeneratedValue annotation]] to specify a primary key generator of type <tt>SEQUENCE</tt>, then you can use the <tt>@SequenceGenerator</tt> annotation to fine-tune this primary key generator to do the following: |
Revision as of 13:38, 18 June 2010
@SequenceGenerator Annotation
If you use the @GeneratedValue annotation to specify a primary key generator of type SEQUENCE, then you can use the @SequenceGenerator annotation to fine-tune this primary key generator to do the following:
- change the allocation size to match your application requirements or database performance parameters;
- change the initial value to match an existing data model (for example, if you are building on an existing data set for which a range of
Attribute | Description | Default | Required? |
---|---|---|---|
name | The name of the generator must match the name of a GeneratedValue with its strategy attribute set to SEQUENCE. | Yes | |
allocationSize | An int value that must match the increment size of the database sequence object. | 50 | No |
initialValue | An int value to start all primary keys. | 0 | No |
sequenceName | A String name of the sequence | SequenceGenerator | No |
This example shows how to use this annotation to specify the allocation size for the SEQUENCE primary key generator named Cust_Seq.
Usage of @SequenceGenerator
@Entity public class Employee implements Serializable { ... @Id @SequenceGenerator(name="Cust_Seq", allocationSize=25) @GeneratorValue(strategy=SEQUENCE, generator="Cust_Seq") @Column(name="CUST_ID") public Long getId() { return id; } ... }
For more information on the EclipseLink artifacts configured by these JPA metadata, refer to Descriptors and Sequencing.