How do I write a MAX query with a where clause in JPA 2.0?

Question

I'm using JPA 2.0. Hibernate 4.1.0.Final, and Java 6. How do I write a JPA query from the following psuedo-SQL?

select max(e.dateProcessed) from Event e where e.org = myOrg

And my domain object looks like the following:

@GenericGenerator(name = "uuid-strategy", strategy = "org.mainco.subco.core.util.subcoUUIDGenerator")
@Entity
@Table(name = "sb__event",
    uniqueConstraints = { @UniqueConstraint(columnNames={"EVENT_ID"}) }
)
public class Event
{

    @Id
    @Column(name = "ID")
    @GeneratedValue(generator = "uuid-strategy")
    private String id;

    @ManyToOne(fetch = FetchType.LAZY, cascade = {CascadeType.REMOVE})
    @JoinColumn(name = "ORGANIZATION_ID", nullable = false, updatable = true)
    private Organization org;

    @Column(name = "DATE_PROCESSED")
    @NotNull
    private java.util.Date dateProcessed;

I know that CriteriaBuilder.greatest is involved, but I just can't figure out how to write the query. This will return all the event objects that match the organization, but that's as far as I've gotten.

final CriteriaBuilder builder = m_entityManager.getCriteriaBuilder();
final CriteriaQuery<Event> criteria = builder.createQuery(Event.class);
final Root<Event> event = criteria.from(Event.class);
criteria.select(event);
criteria.where(builder.equal(Event.get("org"), org));
results.addAll(m_entityManager.createQuery(criteria).getResultList());

score 39 · Accepted Answer · edited Jul 26 '13 at 21:58

39

There are two ways, one using JPQL, the other using criteria queries.
JPQL is simply:

em.createQuery("select max(e.dateProcessed) from Event e where e.org = :myOrg")
  .setParameter("myOrg", myOrg)
  .getSingleResult();

while using criteria you might have:

CriteriaBuilder qb = em.getCriteriaBuilder();
CriteriaQuery<Number> cq = qb.createQuery(Number.class);
Root<Event> root = cq.from(Event.class);
cq.select(qb.max(root.get("dateProcessed")));
cq.where(qb.equal(Event.get("org"), qb.parameter(MyOrgType.class, "myOrg")));
em.createQuery(cq).setParameter("myOrg", myOrg).getSingleResult();

edited Jul 26 '13 at 21:58

Paul Vargas

41,222
15
102
148

answered May 08 '13 at 13:23

Chris

20,138
2
29
43

Since I want to return a "java.util.Date," I assume I change the line "CriteriaQuery cq = qb.createQuery(Number.class);" to "CriteriaQuery cq = qb.createQuery(Date.class);". Either way, I'm getting a compile error on the line "cq.select(qb.max(root.get("dateProcessed")));". It says "Bound mismatch: The generic method max(Expression) of type CriteriaBuilder is not applicable for the arguments (Path – Dave May 15 '13 at 13:17
4

I didn't notice that Max only takes Expression, which is different from the JPQL max expression which will accept any path expression. This is covered in question http://stackoverflow.com/questions/9616390/select-max-timestamp-with-jpa2-criteria-api – Chris May 15 '13 at 13:42
4

When I used "greatest" (changing 'root.get("dateProcessed")' to 'root.get(Event_.dateProcessed)') everything worked great. – Dave May 16 '13 at 19:20

score -1 · Answer 2 · answered Jul 18 '17 at 19:53

With JPQL and CriteriaBuilder

CriteriaBuilder cb = getEntityManager().getCriteriaBuilder();
javax.persistence.criteria.CriteriaQuery cq= getEntityManager().getCriteriaBuilder().createQuery();
Root<T> c = cq.from(getEntityClass());
cq.select(cb.max(c.get("id")));

How do I write a MAX query with a where clause in JPA 2.0?

2 Answers2

Linked