Hibernate HQL to Criteria
I'm trying to translate a simple HQL to Criteria API, can anyone help me? This is my HQL:
SELECT ch FROM Parent p JOIN p.childeren ch WHERE p.id = :id
As a result I get children. Important thing is there there is no relation from Child to Parent. There is only relation in Parent to children like this:
@OneToMany(fetch = FetchType.LAZY, cascade = { CascadeType.ALL })
@JoinColumn(name="parent_id")
private List children;
How can I get the same results using criteria-api?
Only fetching an associated entity is a huge pain using the Criteria API. You would need sub-queries:
DetachedCriteria subCriteria = DetachedCriteria.forClass(Parent.class);
subCriteria.createCriteria("children", "c");
subCriteria.setProjection(Projections.property("c.id"));
subCriteria.add(Restrictions.eq("id", 1));
// Assuming Children is the name of the class
Criteria criteria = sess.createCriteria(Children.class);
criteria.add(Subqueries.propertyIn("id", subCriteria));
criteria.list();
A possible solution for this problem is to use sqlRestriction , as in example below, but this is not nice because it requires to use database column name.
Criteria crit = sessionFactory.getCurrentSession().createCriteria(Child.class); crit.add(Restrictions.sqlRestriction("{alias}.parent_id = ?", parentId, LongType.INSTANCE));
Does someone have a better solution?
你不需要查询这个，因为你可以这样做：
Set<Child> children = session.get(Parent.class, id).getChildren();
children.size(); // trigger lazy initialization