I have an entity called Bucket, and I'm trying to build a criteria query to determine whether there is a Bucket stored with the "Name" property equals to "Bucket_1". So basically it is an exists query.
There is nothing special about the Bucket class, simpler impossible:
Code:
@Entity(name="Bucket")
@Table(name = "BUCKETS")
public class Bucket implements Serializable {
private static final long serialVersionUID = 1L;
@Column(name = "BUCKET_NAME", length=200)
private String Name;
...
}
For the query, this is what I go so far:
Code:
CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
CriteriaQuery<Boolean> superQuery = criteriaBuilder.createQuery(Boolean.class);
Class<? extends T> scopeClass = Bucket.class;
Root<? extends T> root = superQuery.from(scopeClass);
Path<?> attributePath = root.get("Name");
Predicate pred = criteriaBuilder.equal(attributePath, criteriaBuilder.literal("Bucket_1"));
Subquery<? extends T> subQuery = superQuery.subquery(scopeClass);
subQuery.where(pred);
Predicate where = criteriaBuilder.exists(subQuery);
superQuery = superQuery.select(where);
/* This line fails!! */
TypedQuery<Boolean> typedQuery = em.createQuery(superQuery);
boolean result = typedQuery.getSingleResult();
When I execute the query about, I get the following exception on the last line:
Code:
Caused by: java.lang.IllegalStateException: No explicit selection and an implicit one cold not be determined
at org.hibernate.ejb.criteria.QueryStructure.locateImplicitSelection(QueryStructure.java:296)
at org.hibernate.ejb.criteria.QueryStructure.render(QueryStructure.java:249)
at org.hibernate.ejb.criteria.CriteriaSubqueryImpl.render(CriteriaSubqueryImpl.java:281)
at org.hibernate.ejb.criteria.predicate.ExistsPredicate.render(ExistsPredicate.java:57)
at org.hibernate.ejb.criteria.predicate.ExistsPredicate.renderProjection(ExistsPredicate.java:62)
at org.hibernate.ejb.criteria.QueryStructure.render(QueryStructure.java:252)
at org.hibernate.ejb.criteria.CriteriaQueryImpl.render(CriteriaQueryImpl.java:340)
at org.hibernate.ejb.criteria.CriteriaQueryCompiler.compile(CriteriaQueryCompiler.java:223)
at org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:441)
at com.specktro.orchid.io.connection.database.dao.internal.DefaultDAO.has(DefaultDAO.java:426)
... 28 more
I researched a lot but couldn't find anyone with the same error having it explained and/or fixed.
I also tried this way:
Code:
CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
CriteriaQuery<Boolean> superQuery = criteriaBuilder.createQuery(Boolean.class);
Class<? extends T> scopeClass = Bucket.class;
superQuery.from(scopeClass);
Subquery<? extends T> subQuery = superQuery.subquery(scopeClass);
Root<? extends T> root = subQuery.from(scopeClass);
Path<?> attributePath = root.get("Name");
Predicate pred = criteriaBuilder.equal(attributePath, criteriaBuilder.literal("Bucket_1"));
Subquery<? extends T> subQuery = superQuery.subquery(scopeClass);
subQuery.where(pred);
Predicate where = criteriaBuilder.exists(subQuery);
superQuery = superQuery.select(where);
/* This line fails!! */
TypedQuery<Boolean> typedQuery = em.createQuery(superQuery);
boolean result = typedQuery.getSingleResult();
But I get the same exact exception.
Does anyone know why I get this and how to fix this query?Thank you!!
Eduardo
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