Hibernate Query result cannot be cast to List<Subject>

Question

    Session s = ...;
    String query = "from pojo.Subject sub inner join sub.students stu group by "
      + "stu.FName having count(sub.subName) > 1";

    Query q = s.createQuery(query);
    List<Subject> list = q.list();
    for (Subject subj : list) {//error occurs here..
        System.out.println(subj.getSubName()+" - "+subj.getDay());

    }

It gives me an error :

Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to pojo.Subject
    at hibernm.Application.main(Application.java:39)

I know that I can retrieve data by :

  for (int i = 0; i < list.size(); i++) {
        Object get = list.get(i);
        System.out.println(get);

    } 

But it doesn't seem like a proper way for me at all. So I tried with introducing another
list and iterating it :

    List<Subject> myList = new ArrayList<>();
    for (final Object o : q.list()) {
        myList.add((Subject) o);//error occurs here..
    } 

But it gives me the very same result.

So hope you guys get me clear. Thanks in advance.

Answer 1

This is because you are selecting not Subject but inner joined columnset, so it will not give you back List<Subject> instead a list of column arrays including columns of Student as well as Student, possibly a List<Object[]>

So in order to work your query result,you might do like(or try to inspect the query result by debugging):

Query query = session.createQuery(query);
List<Object[]> listResult = query.list();

for (Object[] aRow : listResult) {
    Subject subject = (Subject) aRow[0];
    Student student = (Student) aRow[1];
    //do your code
}