How to resolve Oracle's 'rownum' pseudocolumn with JPA Criteria API?

Question

I would like to get first row from database using JPA Criteria. I use JPA, Hibernate 4.2.7. In SQL, statement looks like:

SELECT * FROM houses WHERE rownum = 1;

My Java code to achive that looks like:

    CriteriaBuilder builder = entityManager.getCriteriaBuilder();
    CriteriaQuery<House> query = builder.createQuery(House.class);
    Root<House> root = query.from(House.class);

    query.select(root).where(builder.equal(root.get("rownum"), 1));

    TypedQuery<House> tQuery = entityManager.createQuery(query); 
    House house = tQuery.getSingleResult();

But 'rownum' pseudocolumn cannot be resolved, I get exception:

 java.lang.IllegalArgumentException: Unable to resolve attribute [rownum] against path
at org.hibernate.ejb.criteria.path.AbstractPathImpl.unknownAttribute(AbstractPathImpl.java:120)
at org.hibernate.ejb.criteria.path.AbstractPathImpl.locateAttribute(AbstractPathImpl.java:229)
at org.hibernate.ejb.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:200)

Is is possible, and if so, how to get 'rownum' pseudocolumn with Criteria API? Thanks for any suggestions.

Answer 1

You can accomplish this using setFirstResult and setMaxResults.

session.createCriteria(Foo.class)
   .setFirstResult(0)
   .setMaxResults(1);

Answer 2

you can set rownum or limits in property of query;

Query q =entityManager.createQuery("select * from employee_table");

q.setFirstResult(0);

q.setMaxResults(30);