JPA：重复使用从序列生成的 ID，用于具有复合 PK（ID + VERSION）的相同 object 的新版本

Question

I have entity A with composite PK [ id(generated from sequence) + version ] .

For a brand new record I want to pick the id from a sequence defined in the DB side. Lets say its created like below

ID     VERSION
1      0

Next time, I want a new version of the same Id to be created like below

ID     VERSION
1      0
1      1

Note: in the second case I don't want it to be generated by the sequence generator, coz I want to manually provide it.

Is it possible in JPA/Hibernate? If possible could someone please tell how to do it?

Many thanks in advance!

Answer 1

Hibernate ORM doesn't support the generation of id with composite keys .

You can probably run a native SQL when you create a new object. With PostgreSQL for example:

Long id = (Long) em.createNativeQuery("SELECT nextval('mysequence')").getSingleResult();
Long version =  ...;

EmbeddedId id = new EmbeddedId(id, version);

Where EmebeddedId is the composite key of your entity:

@Entity
class Example {
   @Id
   EmbeddedId id;

   ...
}

@Embeddable
class EventId implements Serializable {
    Long id;
    Long version;

    ...
}

Where mysequence is the name of a sequence on the database.