I'm trying to use Criteria API in my new project:
public List<Employee> findEmps(String name) {
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Employee> c = cb.createQuery(Employee.class);
Root<Employee> emp = c.from(Employee.class);
c.select(emp);
c.distinct(emp);
List<Predicate> criteria = new ArrayList<Predicate>();
if (name != null) {
ParameterExpression<String> p = cb.parameter(String.class, "name");
criteria.add(cb.equal(emp.get("name"), p));
}
/* ... */
if (criteria.size() == 0) {
throw new RuntimeException("no criteria");
} else if (criteria.size() == 1) {
c.where(criteria.get(0));
} else {
c.where(cb.and(criteria.toArray(new Predicate[0])));
}
TypedQuery<Employee> q = em.createQuery(c);
if (name != null) {
q.setParameter("name", name);
}
/* ... */
return q.getResultList();
}
Now when I change this line:
criteria.add(cb.equal(emp.get("name"), p));
to:
criteria.add(cb.like(emp.get("name"), p));
I get an error saying:
The method like(Expression, Expression) in the type CriteriaBuilder is not > applicable for the arguments (Path, ParameterExpression)
What's the problem?
Perhaps you need
criteria.add(cb.like(emp.<String>get("name"), p));
because first argument of like()
is Expression<String>
, not Expression<?>
as in equal()
.
Another approach is to enable generation of the static metamodel (see docs of your JPA implementation) and use typesafe Criteria API:
criteria.add(cb.like(emp.get(Employee_.name), p));
(Note that you can't get static metamodel from em.getMetamodel()
, you need to generate it by external tools).