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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Entities/Ids/SequenceGenerator"
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<td>'''<tt>sequenceName</tt>'''</td> | <td>'''<tt>sequenceName</tt>'''</td> | ||
<td>A <tt>String</tt> name of the sequence</td> | <td>A <tt>String</tt> name of the sequence</td> | ||
− | <td><tt>SequenceGenerator</tt></td> | + | <td><tt>SequenceGenerator.name</tt></td> |
<td>No</td> | <td>No</td> | ||
</tr> | </tr> |
Revision as of 11:12, 14 June 2011
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Key API
@SequenceGenerator
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; (this should match your database sequence
INCREMENT
) - 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.name | 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="Emp_Seq", allocationSize=25) @GeneratorValue(strategy=SEQUENCE, generator="Emp_Seq") @Column(name="EMP_ID") public Long getId() { return id; } ... }
Example: Using <sequence-generator>
<entity class="Employee"> <attributes> <id name="id"> <generated-value generator="Emp_Seq" strategy="SEQUENCE"/> <sequence-generator name="Emp_Seq" allocationSize="25"/> <column name="EMP_ID"/> </id> ... </attributes> </entity>