A problem of many-to-one query

guteng · **Joined:** Wed Nov 22, 2006 7:56 am **Posts:** 2

I have two tables called "Homework" and "Course". There is a property "course_id" in "Homework" as the foreign key joining the table "Course". And I use Hibernate Synchronizer to general the mapping files and DAO classes. The problem is: I want to get all homework of a course by course_id. The mapping script of the column "course_id" is as bellowed:

Code:

      <many-to-one
         name="Course"
         column="course_id"
         class="Course"
         not-null="true"
         outer-join="true"
         lazy="false"
      >

How to make this query? Thanks very much!

somu_ngm1 · **Joined:** Wed Jun 20, 2007 1:53 am **Posts:** 75

HQL:
------

from HomeWork hw where hw.course=?

Don't use caps for starting letter of property like Course.

Cameron McKenzie · **Posted:** Wed May 14, 2008 10:06 am

I think the most object oriented way is to use the Criteria API. It might look something like this. As you can see, no HQL - just Java objects:

Code:

    Homework homework = new Homework();
    h.setCourse(new Course("Java101");
    Example example = Example.create(homework);
    Session session = HibernateUtil.beginTransaction();
    Criteria criteria = session.createCriteria(Homework.class);
    criteria.add(example);
    List results = criteria.list();
    HibernateUtil.commitTransaction();
    for (int i = 0; i<results.size(); i++) {
      System.out.println(results.get(i).toString());
    }

Here's a free tutorial on the Criteria API if you're interested:

http://www.hiberbook.com/HiberBookWeb/learn.jsp?tutorial=09howtousethecriteriaapi

Good luck!