Correct usage of JPA criteria API, Predicates and where method of CriteriaQuery

Question

I am trying to test a JPA repository. Here is my client/test code:

@Test
    public void testFindBoitesByMultiFieldWithIdentifiantSet() {
        BoiteDataOnDemand dod = new BoiteDataOnDemand();
        Boite boite = dod.getSpecificBoite(0);
        boite.setIdentifiant("theIdentifiant");
        boiteRepository.save(boite);
        assertEquals(10, Boite.countBoites());
        BoiteQueryInfo boiteQueryInfo = new BoiteQueryInfo();
        boiteQueryInfo.setIdentifiant("theIdentifiant");
        List<Boite> boites = boiteRepository.findBoitesByMultiField(boiteQueryInfo, 1, 5, "identifiant", "desc");
        assertEquals(1, boites.size());
    }

Here is the repository method:

@Override
    public List<Boite> findBoitesByMultiField(BoiteQueryInfo boiteQueryInfo, Integer firstResult_, Integer maxResults_, String sort_, String order_) {
        log.debug("findBoitesByMultiField");

        final String identifiant = boiteQueryInfo.getIdentifiant();
        final Date dateOuvertureFrom = boiteQueryInfo.getDateOuvertureFrom();

        CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
        CriteriaQuery<Boite> c = criteriaBuilder.createQuery(Boite.class);
        Root<Boite> boite = c.from(Boite.class);
        List<Predicate> criteria = new ArrayList<Predicate>();
            ...
        if (identifiant != null && !identifiant.trim().equals("")) {
            ParameterExpression<String> parameter = criteriaBuilder.parameter(String.class, "identifiant");
            Predicate condition = criteriaBuilder.like(boite.<String> get("identifiant"), parameter);
            criteria.add(condition);
        }

        if (dateOuvertureFrom != null && dateOuvertureTo != null) {
            ParameterExpression<Date> parameterDateOuvertureFrom = criteriaBuilder.parameter(Date.class, "dateOuvertureFrom");
            ParameterExpression<Date> parameterDateOuvertureTo = criteriaBuilder.parameter(Date.class, "dateOuvertureTo");
            Predicate condition = criteriaBuilder.between(boite.<Date> get("dateOuverture"), parameterDateOuvertureFrom, parameterDateOuvertureTo);
            criteria.add(condition);
        } else if (dateOuvertureFrom != null) {
            ParameterExpression<Date> parameter = criteriaBuilder.parameter(Date.class, "dateOuvertureFrom");
            Predicate condition = criteriaBuilder.greaterThanOrEqualTo(boite.<Date> get("dateOuverture"), parameter);
            criteria.add(condition);
        } else if (dateOuvertureTo != null) {
            ParameterExpression<Date> parameter = criteriaBuilder.parameter(Date.class, "dateOuvertureTo");
            Predicate condition = criteriaBuilder.lessThanOrEqualTo(boite.<Date> get("dateOuverture"), parameter);
            criteria.add(condition);
        }

            ...    
        if (order.equalsIgnoreCase("desc")) {
            c.orderBy(criteriaBuilder.desc(boite.get(sort)));
        } else {
            c.orderBy(criteriaBuilder.asc(boite.get(sort)));
        }

        for (Predicate predicate : criteria) {
            c.where(criteriaBuilder.and(predicate));
        }

        TypedQuery<Boite> q = em.createQuery(c);

        if (identifiant != null && !identifiant.trim().equals("")) {
            q.setParameter("identifiant", "%" + identifiant + "%");
        }

        if (dateOuvertureFrom != null && dateOuvertureTo != null) {
            q.setParameter("dateOuvertureFrom", dateOuvertureFrom);
            q.setParameter("dateOuvertureTo", dateOuvertureTo);
        } else if (dateOuvertureFrom != null) {
            q.setParameter("dateOuvertureFrom", dateOuvertureFrom);
        } else if (dateOuvertureTo != null) {
            q.setParameter("dateOuvertureTo", dateOuvertureTo);
        }

            ...    
        return q.setFirstResult(firstResult).setMaxResults(maxResults).getResultList();
    }

However, the test always fails at assertEquals(1, boites.size()); indicating that no result is returned i.e. (java.lang.AssertionError: expected:<1> but was:<0>).

I strongly suspect something is wrong here:

for (Predicate predicate : criteria) {
            c.where(criteriaBuilder.and(predicate));
        }

But I am not sure how to "and" the criteria.

Can anyone please provide advice?

P.S. FYI, BoiteDataOnDemand inserts random 10 rows into the boite table.

EDIT: code was edited to make it shorter.

Answer 1

Starting from your hint in the final part of your post, I agree that the way you are adding predicates for the where clause is not correct.

I see two ways of proceeding:

First way

Using an array of predicates

List<Predicate> predicates = new ArrayList<Predicate>();
for (Key key : keys) {
    predicates.add(criteriaBuilder.equal(root.get(key), value));
}
c.where(criteriaBuilder.and(predicates.toArray(new Predicate[] {})));

Second way

Modifying the same predicate in the loop

Predicate predicate = criteriaBuilder.conjunction();
for (Key key : keys) {
    Predicate newPredicate = criteriaBuilder.equal(root.get(key), value);
    predicate = criteriaBuilder.and(predicate, newPredicate);
}
c.where(predicate);

---

EDITED

After looking again your code sample, I see that you have already created in the correct way a list of PredicateS: you have called it criteria. You are only using them in the wrong way. See the last line of my first example.

---

EDIT 2

In order to see if the problem is generated by the use of PredicateExpressionS, that are not specifically needed in your case, try to temporarily remove them. Modify your first criteria from

if (identifiant != null && !identifiant.trim().equals("")) {
    ParameterExpression<String> parameter = criteriaBuilder.parameter(String.class, "identifiant");
    Predicate condition = criteriaBuilder.like(boite.<String> get("identifiant"), parameter);
    criteria.add(condition);
}

to

if (identifiant != null && !identifiant.trim().equals("")) {
    Predicate condition = criteriaBuilder.like(boite.get("identifiant"), "%" + identifiant + "%");
    criteria.add(condition);
}