Hibernate JPA Sequence (non-Id)
hibernate, java, jpa, sequence
Solution
Looking for answers to this problem, I stumbled upon this link
It seems that Hibernate/JPA isn't able to automatically create a value for your non-id-properties. The `@GeneratedValue` annotation is only used in conjunction with `@Id` to create auto-numbers.
The `@GeneratedValue` annotation just tells Hibernate that the database is generating this value itself.
The solution (or work-around) suggested in that forum is to create a separate entity with a generated Id, something like this:
@Entity
public class GeneralSequenceNumber {
@Id
@GeneratedValue(...)
private Long number;
}
@Entity
public class MyEntity {
@Id ..
private Long id;
@OneToOne(...)
private GeneralSequnceNumber myVal;
}
Problem
Is it possible to use a DB sequence for some column that is not the identifier/is not part of a composite identifier? I'm using hibernate as jpa provider, and I have a table that has some columns that are generated values (using a sequence), although they are not part of the identifier. What I want is to use a sequence to create a new value for an entity, where the column for the sequence is NOT (part of) the primary key: ``` @Entity @Table(name = "MyTable") public class MyEntity { //... @Id //... etc public Long getId() { return id; } //note NO @Id here! but this doesn't work... @GeneratedValue(strategy = GenerationType.AUTO, generator = "myGen") @SequenceGenerator(name = "myGen", sequenceName = "MY_SEQUENCE") @Column(name = "SEQ_VAL", unique = false, nullable = false, insertable = true, updatable = true) public Long getMySequencedValue(){ return myVal; } } ``` Then when I do this: ``` em.persist(new MyEntity()); ``` the id will be generated, but the `mySequenceVal` property will be also generated by my JPA provider. Just to make things clear: I want Hibernate to generate the value for the `mySequencedValue` property. I know Hibernate can handle database-generated values, but I don't want to use a trigger or any other thing other than Hibernate itself to generate the value for my property. If Hibernate can generate values for primary keys, why can't it generate for a simple property?