Java – Hibernate: make database only if not exists

If you are using the JPA annotations, you can use @PrePersist and @PreUpdate event hooks do this:

@Entity
@Table(name = "entities")    
public class Entity {
  ...

  private Date created;
  private Date updated;

  @PrePersist
  protected void onCreate() {
    created = new Date();
  }

  @PreUpdate
  protected void onUpdate() {
    updated = new Date();
  }
}

or you can use the @EntityListener annotation on the class and place the event code in an external class.

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;
}