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

Question

I want a JPA/Hibernate (preferably JPA) annotation that can generate the value of a column, that is not a primary key and it doesn\'t start from 1.

From what I have

Answer 1

Related to @Vlad Mihalcea, now you can use @GeneratorType to generate your own custom value for non id column. For example:

1. Entity:

    import org.hibernate.annotations.GeneratorType

    @GeneratorType(type = CustomGenerator.class, when = GenerationTime.INSERT)
    @Column(name = "CUSTOM_COLUMN", unique = true, nullable = false, updatable = false, lenght = 64)
    private String custom;

2. ValueGenerator implementation:

public class CustomGenerator extends ValueGenerator {
        private static final String TODAY_EXAMPLE_QUERY = "from Example where createDate>:start and createDate<:end order by createDate desc";
        private static final String START_PARAMETER = "start";
        private static final String END_PARAMETER = "end";
        private static final String NEXTVAL_QUERY = "select EXAMPLE_SEQ.nextval from dual";
        private final SimpleDateFormat dataFormat = new SimpleDateFormat("yyyyMMdd");

        @Override
        public String generateValue(Session session, Object owner) {
            Date now = new Date();
            Query todayQuery = session.createQuery(TODAY_EXAMPLE_QUERY, Example.class);
            query.setParameter(START_PARAMETER, start(now));
            query.setParameter(END_PARAMETER, end(now));
            Example lastExample = todayQuery.setMaxResult(1).setHibernateFlushMode(COMMIT).uniqueResult();

            NativeQuery nextvalQuery = session.createSQLQuery(NEXTVAL_QUERY);
            Number nextvalValue = nextvalQuery.setFlushMode(COMMIT).uniqueResult();
            return dataFormat.format(now) + someParameter(lastExample) + nextvalValue.longValue();
        }
    }