How to use existing Oracle sequence to generate id in hibernate?

Question

I have legacy Oracle db with a sequence named PRODUCT_ID_SEQ.

Here is the mapping of Product class for which I need generate correct ids:<

Answer 1

I had the same issue while upgrading from 3.5.5 to 5.0.6.Final.

I solved it by re-configuring mapping in the HBM file from:

    <generator class="sequence">
        <param name="sequence">PRODUCT_ID_SEQ</param>
    </generator>

to:

    <generator class="org.hibernate.id.enhanced.SequenceStyleGenerator"> 
        <param name="prefer_sequence_per_entity">true</param> 
        <param name="optimizer">none</param>
        <param name="increment_size">1</param>
        <param name="sequence_name">PRODUCT_ID_SEQ</param>
    </generator>

Answer 2

I use following on PostgreSQL and works just fine.

 @Id
 @GeneratedValue(generator = "my_gen")
 @SequenceGenerator(name = "my_gen", sequenceName = "my_seq_in_db")
 private int userId;

Answer 3

I'm not used to use annotations, this is what I have in my *.hbm.xml:

<id name="id" type="java.lang.Integer">
    <column name="ID_PRODUCT" />
    <generator class="sequence-identity" >
        <param name="sequence">PRODUCT_ID_SEQ</param>
    </generator>
</id>

You can easily map this to annotations. The generator sequence-identity uses auto increment with sequences.

Answer 4

The answer to the original question:

@SequenceGenerator(name="EL_SEQ", sequenceName="EL_SEQ",allocationSize=1)

It is allocationSize that sets the value to increment by.