Criteria Builder returning different kind of object with a count generated value for a column? - jpql

Question

I am facing this difficult.
I have this method:
public List findEmployees(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(true);
Join<Employee,Project> project =
emp.join("projects", JoinType.LEFT);
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();
}
Basically, here I am getting the Employee.
What I want is to have an object different than employee, employee is related with projects and I want to return an object EmployeeProjectCount
That is basically an object with:
id (from employee)
name (from employee)
numberProjects (is the count of the related projects to an employee)
Projects is a table with a column named "employee" that makes the relation.
I am wondering if at my criteria builder I can do that, a count of the related fields
Is it possible to return a different object?
I cannot do this:
TypedQuery<EmployeeProjectCount> q = em.createQuery(c);
my jpql query is like this:
select e.id as id, e.name as name, count(e) as total
from
Employee e
left join Project p on p.employee = e.id group by e;
Is there any way to do it?

Answer 1

What you want to use is the construct method from CriteriaBuilder. It does exactly what you would otherwise use in jpql. You define the output class, and define the data that is used for it.
Here is a nice example of how to do this: How to select a POJO with a Criteria Query