Latest revision as of 11:41, 21 November 2017

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Key API

• @GeneratedValue
• @SequenceGenerator

@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

The following example shows how to use this annotation to specify the allocation size for the SEQUENCE primary key generator named Emp_Seq.

Example: @SequenceGenerator

 @Entity
 public class Employee implements Serializable {
     ...
     @Id
     @SequenceGenerator(name="Emp_Seq", allocationSize=25)
     @GeneratedValue(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">
            <column name="EMP_ID"/>
            <generated-value generator="Emp_Seq" strategy="SEQUENCE"/>
            <sequence-generator name="Emp_Seq" allocationSize="25"/>
        </id>
        ...
    </attributes>
</entity>

@TableGenerator	Configuring Entities	@UuidGenerator
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