Java Hibernate Fetch Entity loads on setting a property on it

Question

i am trying to get some students in Hibernate in many-to-one relationship School-Students. later i am trying to get the Teachers of the school when the students belongs..

here is my code

public ArrayList<Student>search(Date dateBorn)
{
    Session session = currentSession();
    Criteria criteria = session.createCriteria(Student.class).add(prepareForSelect()).setFetchMode("school",FetchMode.JOIN);        
    criteria.add(Restrictions.ge("age",dfrom))        
    .setProjection(addProjection("id","name","lastname","phone","school"))// the only data i need
    .setResultTransformer(transformer(Student.class));
    ArrayList<Student>students= new ArrayList<Student>(criteria.list());
    if (!students.isEmpty())                
        for (Student student:students) loadTeachersForSchool(session,student,student.getSchool().getId());
    return students;
}
private void loadTeachersForSchool(final Session session,final Student student,Integer schoolID)
{
    Criteria like = session.createCriteria(Teacher.class).add(prepareForSelect().
    add(Restrictions.eq("School.id",schoolID)))
    .setProjection(addProjection("id","name","lastname"))//// the only data i need
    .setResultTransformer(transFormer(Teacher.class));                
    student.getSchool().setTeacherList(new java.util.LinkedHashSet<Teacher>(like.list()));
    return;
}

everything works like a charm as you can see i am bringing only the ID of the school because is the only thing i need so far and is working

later when i try to set the teacher to the school using this code:

student.getSchool().setTeacherList(new java.util.LinkedHashSet<Teacher>(like.list()));
return;

hibernate generates a SELECT bringing ALL the SCHOOL i load the ID on it because is the only thing i need...

in the line

student.getSchool()

this gets me into trouble because i dont need all this data and is quite long 50 fields and is degrading my performance what can i do we are using Open Session in View that's why i dont close the session and i using Hibernate 4.2.3 with MySQL 5.

i could get the desired behavior declaring the property as public and accessing directly but of course is not what i want.

student.getSchool().setTeacherList=new java.util.LinkedHashSet<Teacher>(like.list());

please help me.

score 0 · Answer 1 · edited Jun 20 '20 at 09:12

Solution

i decided to create a School instance by my self is quite easy i know i am losing some benefits from hibernate but i dont need it at this point this is my solution. i hope helps somebody.

private void loadTeachersForSchool(final Session session,final Student student,Integer  schoolID)
{
   School school = new School(idSchool);
   Criteria like = session.createCriteria(Teacher.class).add(prepareForSelect().
   add(Restrictions.eq("School.id",schoolID)))
   .setProjection(addProjection("id","name","lastname"))//// the only data i need
   .setResultTransformer(transFormer(Teacher.class));                
   school.setTeacherList(new java.util.LinkedHashSet<Teacher>(like.list()));
   student.setSchool(school);
  return;
}

this solves the trick.. and i dont load the school from DB.

check the important points.

School school = new School(idSchool);//create the school instance and and the teachers
school.setTeacherList(new java.util.LinkedHashSet<Teacher>(like.list()));
student.setSchool(school);//and add all to students

Java Hibernate Fetch Entity loads on setting a property on it

1 Answers1

Solution