How Can I Generate Database Sequence Values for Non-ID Columns in Hibernate?

Hibernate Sequence for Non-ID Columns

Using database sequences to generate values for non-primary key columns in Hibernate is a common requirement. Unfortunately, hibernate currently provides no built-in method for achieving this.

The @GeneratedValue annotation can only be used in conjunction with @Id to auto-generate values for primary keys. The challenge arises because Hibernate assumes that non-ID properties should be handled by the user application.

To overcome this limitation, a workaround involves creating a separate entity with an auto-generated Id. This entity then becomes responsible for generating the sequence value that can be assigned to the non-ID property in the target entity.

Consider the following example:

@Entity
public class GeneralSequenceNumber {
  @Id
  @GeneratedValue(...)
  private Long number;
}

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

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

In this scenario, a new instance of GeneralSequenceNumber is created, and its number field is auto-generated. This value is then assigned to the myVal property in MyEntity during entity persistence.

While this workaround adds an extra entity, it provides a solution for managing non-ID property sequences in Hibernate. Until a more seamless approach is implemented, this method offers a practical solution to this common use case.

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