QueryDSL and JPA 2.1 Entity Graph

Question

In my Spring Data/JPA query I need to add filtering with many criteria and the user can choose whatever he want.

Is there a way to get working together QueryDSL and JPA 2.1 Entity Graph ? If so, could you please show an example ?

Answer 1

This is some code from my project using JPA Criteria API. Main idea that user can choose any field as filter and in service layer all filters are passed as List<Map<String, Object>>, where String key in map is a name of field and Object value is filter value. Maybe it will be helpfull:

public List<DocumentsShort> findAllByCriteria(Integer firstResult, Integer maxResult, String sort, String condition, List<Map<String, Object>> conditions) {
    CriteriaBuilder cb = entityManager.getCriteriaBuilder();
    CriteriaQuery<EntityClass> criteriaQuery = cb.createQuery(EntityClass.class);
    Root<EntityClass> root = criteriaQuery.from(EntityClass.class);
    Join<EntityClass, AnotherEntityClass> AnotherEntityClassJoin = root.join("fieldOfEntity", JoinType.LEFT);
    Predicate predicate = cb.conjunction();
    List<Predicate> predicateList = new ArrayList<>();
    for (Map<String, Object> map : conditions) {
        Predicate tempPredicate = cb.conjunction();
        tempPredicate = cb.and(predicate, cb.equal(root.get("deleted"), 0)); // only entities not marked as deleted
        for (Map.Entry<String, Object> entry : map.entrySet()) {
            String key = entry.getKey();
            Path pathToField = null;
            pathToField = root.get(key);
            Object value = entry.getValue();
            if (value == null) {
                tempPredicate = cb.and(tempPredicate, cb.isNull(pathToField));
            } else if (value instanceof String) {
                tempPredicate = cb.and(tempPredicate, cb.like(pathToField, "%" + value + "%"));
            } else if (value instanceof List) {
                tempPredicate = cb.and(tempPredicate, pathToField.in(((List) value)));
            } else {
                tempPredicate = cb.and(tempPredicate, cb.equal(pathToField, value));
            }
        }
        predicateList.add(tempPredicate);
    }
    criteriaQuery.where(cb.or(predicateList.toArray(new Predicate[predicateList.size()])));
    TypedQuery query = entityManager.createQuery(criteriaQuery);
    query.setFirstResult(firstResult != null ? firstResult : 0);
    query.setMaxResults(maxResult != null ? maxResult : 500);

    return query.getResultList();
}