Hibernate Mapping returns multiple identical objects when running paged queries with extra Criteria

Question

So I keep coming up short on this, and just can't seem to get it to work right.

Things seem to work fine when I use my HibernateUtil.get(clazz, pkId) method, but when I try using the HibernateUtil.pagedQuery(clazz, criterion, start, stop) I get multiple identical objects returned.

For example if there were 3 employees assigned to Role 1, then running...

Role role = HibernateUtil.get(Role.class, new Integer(1));

... works as expected. However, if I run...

List<Criterion> c = new ArrayList();
c.add(Restrictions.eq("roleTypeSeqNo", new Integer(1)));
List<Role> roles = (List<Role>) phi.util.hibernate.HibernateUtil.pagedQuery(Role.class, c, 0, 50);

... returns a List of 3 identical roles. All of which represent Role 1.

If someone could guide me down the right path, I would really appreciate it.

Thanks in advance!

Here's an abbreviated version of my classes

@Entity
@Table(name="ASSIGNMENTS")
public class Assignment implements Serializable {
  @EmbeddedId
  private AssignmentPK pk;
  // After coming across many errors I finally caved and reverted roleTypeSeqNo back to just an Integer.
  private Integer roleTypeSeqNo;
  private String status;
  private String location;
}

@Embeddable
public class AssignmentPK implements Serializable {
  @ManyToOne
  @JoinColumn(name="EMPLID")
  private Employee employee;
  @Column(name="PRIORITY_NO")
  private String priorityNo;
}

@Entity
public class Employee implements Serializable {
  @Id
  private Integer emplId;
  private String name;
}

@Entity
public class Role implements Serializable {
  @Id
  private Integer roleTypeSeqNo;
  private Integer reportsToRole;
  @OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="roleTypeSeqNo")
  @JoinTable(
      name="ASSIGNMENTS"
      , joinColumns={@JoinColumn(name="ROLE_TYPE_SEQ_NO")}
      , inverseJoinColumns={
          @JoinColumn(name="EMPLID"),
          @JoinColumn(name="PRIORITY_NO")
      }
  )
  private List<Assignment> assignments;
}

public class HibernateUtil {
    public static Object get(Class clazz, Serializable pkId) {
        Session session = getSession();
        Transaction transaction = session.beginTransaction();

        Object obj = session.get(clazz, pkId);

        transaction.commit();
        session.close();

        return obj;
    }

    public static List pagedQuery(Class clazz, List<Criterion> criterion, Integer start, Integer size){
        Session session = getSession();
        try {
            Transaction transaction = session.beginTransaction();

            DetachedCriteria dCriteria = DetachedCriteria.forClass(clazz);
            for(Criterion c : criterion){
                dCriteria.add(c);
            }
            dCriteria.setResultTransformer(CriteriaSpecification.DISTINCT_ROOT_ENTITY);
            dCriteria.setProjection(Projections.id());

            Criteria criteria=session.createCriteria(clazz);
            criteria.add(Subqueries.propertyIn("id", dCriteria));
            criteria.setFirstResult(start);
            criteria.setMaxResults(size);

            List records = criteria.list();

            transaction.commit();

            return records;
        } catch (Exception e) {
            Logger.getLogger("HibernateUtil").log(Level.SEVERE, "There was an EXCEPTION THROWN!!!", e);
            return null;
        } finally  {
            session.close();
        }
    }
}

can you please post your mapping file ?

rags
– rags

2012-04-26 04:51:47 +00:00
Commented Apr 26, 2012 at 4:51 — rags
– rags, Commented Apr 26, 2012 at 4:51
I don't have a mapping file. I'm using annotations.

hypno7oad
– hypno7oad

2012-04-26 14:36:22 +00:00
Commented Apr 26, 2012 at 14:36 — hypno7oad
– hypno7oad, Commented Apr 26, 2012 at 14:36

Firo · Accepted Answer · 2012-04-26 09:50:30Z

5

dCriteria.setResultTransformer(CriteriaSpecification.DISTINCT_ROOT_ENTITY);

should be on the main criteria

criteria.setResultTransformer(CriteriaSpecification.DISTINCT_ROOT_ENTITY);

Also there is no need for the subquery there. The following is enough

    Criteria criteria = session.createCriteria(clazz);

    for(Criterion c : criterions){
        criteria.add(c);
    }

    criteria.setFirstResult(start);
    criteria.setMaxResults(size);

    List records = criteria.list();

answered Apr 26, 2012 at 9:50

Firo

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2 Comments

jhegedus Over a year ago

Can you please explain why is this needed? What is CriteriaSpecification.DISTINCT_ROOT_ENTITY doing ? In which situations do we get multiple results for the same object?

Firo Over a year ago

if you join a parent table and a child table (1-n) together the parent records are duplicated SELECT p.*, c.* FROM parenttable p JOIN childtable c ON p.Id = c.parent_id. Hibernate will emit a listelement per row returned but will use the same reference if the parentrecord is the same. DISTINCT_ROOT_ENTITY filters duplicate parent objects in the result so you get a list of distinct parent objects back.

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