hibernate JPA: optional value generation

Question

Is it possible to set a filed in hibernate to have a value generated whenever it is null?

This is not the primary key but business key. Basically I have a container with a barcode field. If no barcode is assigned, generate it automatically (eg, prefix + sequence number).

Is that possible or do I need to create a custom method for accessing the next sequence value?

Answer 1

Have a look at this: Hibernate JPA Sequence (non-Id) The idea is to create an entity for the generated value BarCode and then use it as a property of your main entity:

@Entity
public class BarCode{

    private static final String PREFIX = "PREFIX";

    @Id
    @GeneratedValue(...)
    private Long number;

    public String getBarCodeValue(){
        return PREFIX + getNumber();
    }
}

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

    @OneToOne(...)
    private BarCode barCode;

    public String getBarCodeValue(){
        return barCode.getBarCodeValue();
    }
}