My custom order by in criteria query/jpql

Is it possible to do my custom order by using criteria query or jpql in Java? In my table, I have a column – number type(for now, this column includes numbers such as 1, 2, 3, 5, 10). I would like to sort result in this order 2, 5, 1, 10, 3.

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<MyEntity> cq = cb.createQuery(MyEntity.class);
Root<MyEntity> root = cq.from(MyEntity.class);

cq.select(root);
cq.where(cb.equal(root.get("someMyFields"), "myExpectedFieldValue"));
cq.orderBy(cb.asc(root.get("myNumberField"))); // how can I sort result in this order 2, 5, 1, 10, 3?

TypedQuery<MyEntity> query = em.createQuery(cq);
query.setFirstResult(0);
query.setMaxResults(200);

return query.getResultList();

How can I do it?

Answer

You have to use a CASE expression in your ORDER BY clause to implement this kind of “sort indirection”. In SQL and JPQL, this would be:

ORDER BY CASE myNumberField 
  WHEN 2  THEN 1
  WHEN 5  THEN 2
  WHEN 1  THEN 3
  WHEN 10 THEN 4
  WHEN 3  THEN 5
          ELSE 6
END

With the criteria API, using CriteriaBuilder.selectCase()

cq.orderBy(
  qb.selectCase(root.get("myNumberField"))
    .when(qb.literal(2), qb.literal(1))
    .when(qb.literal(5), qb.literal(2))
    .when(qb.literal(1), qb.literal(3))
    .when(qb.literal(10), qb.literal(4))
    .when(qb.literal(3), qb.literal(5))
    .otherwise(qb.literal(6))
    .getExpression()
    .asc());

Of course, a much better solution is to normalise these values in a separate table that you can join just for the ordering:

SELECT *
FROM t
JOIN orderings o ON t.myNumberField = o.myNumberField
ORDER BY o.orderDefinition