Hibernate JPA Sequence (Non-Id)

Hibernate JPA Sequence (non-Id)

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;
}

How to use a sequence generator for a non ID field?

Check the value of result returned from the generate method in SequenceControlNumberclass.

BTW check this response in this SO question : Hibernate JPA Sequence (non-Id)

JPA or Hibernate to generate a (non primary key) column value, not starting from 1

Here's what worked for me - we coded all of it in the service.
Here's the entity:

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class Registrant extends AbstractEntity {
    //....
    private long invoiceNumber;//invoice number

    @Entity
    public static class InvoiceNumberGenerator {
        @Id
        @GeneratedValue
        private int id;
        private long counter;

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        public long getCounter() {
            return counter;
        }

        public void setCounter(long counter) {
            this.counter = counter;
        }
    }
}

And then we have a service that does the magic (actually there's no magic, all is done manually):

public synchronized Registrant save(Registrant registrant) {
    long counter = getInvoiceNumber();
    registrant.setInvoiceNumber(counter);

    return registrantRepository.save(registrant);
}

private long getInvoiceNumber() {
    //mist: get the invoice number from the other table
    long count = registrantInvoiceNumberGeneratorRepository.count();
    if(count > 1) {
        throw new RuntimeException(": InvoiceNumberGenerator table has more than one row. Fix that");
    }

    Registrant.InvoiceNumberGenerator generator;
    if(count == 0) {
        generator = new Registrant.InvoiceNumberGenerator();
        generator.setCounter(1000001);
        generator = registrantInvoiceNumberGeneratorRepository.save(generator);
    } else {
        generator = registrantInvoiceNumberGeneratorRepository.findFirstByOrderByIdAsc();
    }

    long counter = generator.getCounter();
    generator.setCounter(counter+1);
    registrantInvoiceNumberGeneratorRepository.save(generator);
    return counter;
}

Note the synchronized method - so that nobody can get the same number.

I can't believe there's nothing automatic that can do that.

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