Notice: This Wiki is now read only and edits are no longer possible. Please see: https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/wikis/Wiki-shutdown-plan for the plan.
Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Entities/Ids/SequenceGenerator"
< EclipseLink | UserGuide | JPA | Basic JPA Development
m |
m |
||
Line 37: | Line 37: | ||
}} | }} | ||
− | |||
− | < | + | The following example shows how to use this annotation to specify the allocation size for the <tt>SEQUENCE</tt> primary key generator named <tt>Cust_Seq</tt>. |
− | '' | + | |
+ | ======'' Example: @SequenceGenerator''====== | ||
<source lang="java"> | <source lang="java"> | ||
@Entity | @Entity |
Revision as of 13:32, 29 March 2011
EclipseLink JPA
EclipseLink | |
Website | |
Download | |
Community | |
Mailing List • Forums • IRC • mattermost | |
Issues | |
Open • Help Wanted • Bug Day | |
Contribute | |
Browse Source |
@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 |
The following example shows how to use this annotation to specify the allocation size for the SEQUENCE primary key generator named Cust_Seq.
Example: @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.