Hibernate | Academia

The following code will return one result based on 2 criteria:

process entity attribute to be equal with process parameter
state entity attribute to be equal with state parameter from function

Entity has these two attributes of type ENUM: process and state.

DB Table consist in a map between process and allowed states. Method findByType will return the correct entry based on one process and one state:

@Service
public class JpaStateMachineDaoImpl implements JpaStateMachineDao {

	@PersistenceContext
	private EntityManager em;

	@Override
	public StateMachineEntity findByType(SmProcess process, SmState state) {
		CriteriaBuilder cb = em.getCriteriaBuilder();
		CriteriaQuery<StateMachineEntity> cq = cb.createQuery(StateMachineEntity.class);
		Root<StateMachineEntity> model = cq.from(StateMachineEntity.class);

		List<Predicate> predicateList = new ArrayList<Predicate>();

		Predicate processPredicate = cb.equal(model.get("process"), process.ordinal());
		Predicate statePredicate = cb.equal(model.get("state"), state.ordinal());
		predicateList.add(processPredicate);
		predicateList.add(statePredicate);

		Predicate[] predicates = new Predicate[predicateList.size()];
		predicateList.toArray(predicates);
		cq.where(predicates);

		TypedQuery<StateMachineEntity> q = em.createQuery(cq);
		return q.getSingleResult();
	}
}

@Service

public class JpaStateMachineDaoImpl implements JpaStateMachineDao {

@PersistenceContext

private EntityManager em;

@Override

public StateMachineEntity findByType(SmProcess process, SmState state) {

CriteriaBuilder cb = em.getCriteriaBuilder();

CriteriaQuery<StateMachineEntity> cq = cb.createQuery(StateMachineEntity.class);

Root<StateMachineEntity> model = cq.from(StateMachineEntity.class);

List<Predicate> predicateList = new ArrayList<Predicate>();

Predicate processPredicate = cb.equal(model.get("process"), process.ordinal());

Predicate statePredicate = cb.equal(model.get("state"), state.ordinal());

predicateList.add(processPredicate);

predicateList.add(statePredicate);

Predicate[] predicates = new Predicate[predicateList.size()];

predicateList.toArray(predicates);

cq.where(predicates);

TypedQuery<StateMachineEntity> q = em.createQuery(cq);

return q.getSingleResult();

}

Example of DAO implementation for Hibernate Criteria Query -> Find By Id

...
@Repository
public class JpaModelDaoImpl implements JpaModelDao {

    @PersistenceContext
    private EntityManager em;

    ...
	@Override
	public ModelEntity findById (int modelId) {
		CriteriaBuilder cb = em.getCriteriaBuilder();
		CriteriaQuery<ModelEntity> cq = cb.createQuery(ModelEntity.class);
		Root<ModelEntity> model = cq.from(ModelEntity.class);
		cq.where(cb.equal(model.get("id"), modelId));
		TypedQuery<ModelEntity> q = em.createQuery(cq);
		return q.getSingleResult();
	}
    ...
}

...

@Repository

public class JpaModelDaoImpl implements JpaModelDao {

@PersistenceContext

private EntityManager em;

...

@Override

public ModelEntity findById (int modelId) {

CriteriaBuilder cb = em.getCriteriaBuilder();

CriteriaQuery<ModelEntity> cq = cb.createQuery(ModelEntity.class);

Root<ModelEntity> model = cq.from(ModelEntity.class);

cq.where(cb.equal(model.get("id"), modelId));

TypedQuery<ModelEntity> q = em.createQuery(cq);

return q.getSingleResult();

}

...

}

Model class has attribute: id

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Category Archives: Hibernate

Criteria Query – predicate

Criteria Query – find by id

by JadeBaboon Team