Spring Data JPA - JPQL query by given class - spring

Question

I have a specific exercise to do within my university classes homework.
Given entity structure like this:
#Entity
#Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class Parent {
...some fields...
}
#Entity
public class ChildA extends Parent {
...
}
#Entity
public class ChildB extends Parent {
...
}
I have to implement JpaRepository method in ParentRepository or rather JPQL Query to perform update operation on table specified by Class<? extends Parent> parameter. Simply, method should update some field but only in a subclass given as a parameter.
The method structure should be:
public interface ParentRepository extends JpaRepository<Parent, Integer> {
void updateInBulk(Class<? extends Parent> clazz, int someParameter);
}
I came up with something like this, but it didn't work.
public interface ParentRepository extends JpaRepository<Parent, Integer> {
#Modifying
#Query("update :entity e set e.some_field = 'T' where e.other_field > :some_param")
void updateInBulk(#Param("entity") Class<? extends Parent> clazz, #Param("some_param") int someParam);
}
It was just my blind shot, but I could not find any materials which explain how to do stuff like this.
Does anybody have any suggestion how to solve this task?

Answer 1

You'll wouldn't do this with JPQL, but you'd rather want to write a Criteria query for that - which you can add to your JPARepository as well. Something like (you need to adjust this to your needs.)
public void updateInBulk(Class<? extends Parent> clazz, String someParameterName , int someValue) {
CriteriaBuilder cb = this.em.getCriteriaBuilder();
// create update
CriteriaUpdate<Order> update = cb.createCriteriaUpdate(clazz);
// set the root class
Root e = update.from(clazz);
// set update and where clause
update.set(someParameterName, someValue);
// update.where(cb.greaterThanOrEqualTo(e.get(someParameterName), oldValue));
// perform update
this.em.createQuery(update).executeUpdate();
}