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

If you use javax.persistence.SequenceGenerator, hibernate use hilo and will possibly create large gaps in the sequence. There is a post addressing this problem: https://forum.hibernate.org/viewtopic.php?t=973682

there are two ways to fix this problem

1. In the SequenceGenerator annotation, add allocationSize = 1, initialValue= 1

2. instead of using javax.persistence.SequenceGenerator, use org.hibernate.annotations, like this:

   @javax.persistence.SequenceGenerator(name = "Question_id_sequence", sequenceName = "S_QUESTION")

   @org.hibernate.annotations.GenericGenerator(name="Question_id_sequence", strategy = "sequence", parameters = { @Parameter(name="sequence", value="S_QUESTION") } )

I have tested both ways, which works just fine.