How Can I Generate Database Sequences for Non-ID Columns in Hibernate JPA?

Using a Database Sequence for Non-ID Columns in Hibernate JPA

When working with Hibernate as the JPA provider, you may encounter the need to generate values for columns that are not part of the identifier. Unfortunately, the @GeneratedValue annotation, commonly used for auto-incrementing primary keys, is not applicable in this scenario.

Firstly, it's important to understand that Hibernate/JPA does not automatically generate values for non-ID properties. The @GeneratedValue annotation is solely used for managing primary key generation. Instead, database-generated values are expected.

To overcome this limitation, consider creating a separate entity with a generated identifier, known as a "Surrogate Key Entity." The Non-ID column in question can then be associated with this surrogate entity using a OneToOne relationship.

Example Implementation:

// Surrogate Key Entity
@Entity
public class SurrogateEntity {
  @Id
  @GeneratedValue(...)
  private Long number;
}

// Main Entity
@Entity
public class MyEntity {
  @Id
  private Long id;

  @OneToOne(...)
  private SurrogateEntity myVal;
}

With this approach, the value for the myVal property will be generated by the database upon creation of a new MyEntity instance. This work-around allows you to utilize Hibernate's database-generated value handling capabilities for non-ID columns.

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