Question

I have a MySQL database includes a table named ‘Task’. and I used Hibernate to map the data to the database.

it includes these fields : id, user_id, project_id, deliverable_id, activity_id, …

When I retrieve Tasks from Db, I need to sort them by Project at first, and then by Deliverable and finally by Activty.

         Session session = HibernateUtil.getSessionFactory().getCurrentSession();
            session.beginTransaction();
            List<Task> tasks = (List<Task>)session.createQuery(
"from Task as t where t.user.username = :name order by t.project.key ASC").setString("name", username).list();
            orderByDeliverable(tasks);
            orderByActivity(tasks);



    private void orderByDeliverable(List<Task> tasks) {
       Collections.sort(tasks, new Comparator<Task>(){   
          public int compare(Task t1, Task t2) {
             if(t1.getProject().getId() == t2.getProject().getId()) 
               return t1.getDeliverable().getKey().compareToIgnoreCase(t2.getDeliverable().getKey());
             return 0;
          }
       });
    }

    private void orderByActivity(List<Task> tasks) {
        Collections.sort(tasks, new Comparator<Task>(){  
           public int compare(Task t1, Task t2) {
              if(t1.getProject().getId() == t2.getProject().getId()) 
             if(t1.getDeliverable().getId() == t2.getDeliverable().getId()) 
                return t1.getActivity().getKey().compareToIgnoreCase(t2.getActivity().getKey());
            return 0;
           }
       });
    }

As you see in the code I used two methods to sort them by deliverable and activity, but I sort them by project in the Query.

I am not good in Query writing, do you know any way that I can do all sorting stuff in the query and get the same result ?

Answer 1

I found the answer. I just need to use this query:

tasks = (List<Task>)session.createQuery("from Task as t where t.user.username = :name 
order by t.project.key ASC, t.deliverable.key ASC, t.activity.key ASC")
.setString("name", username).list();

It worked the same for me.

Actually I looked for this solution to speed-up the application that I have developed.
I tested that which one is faster. The result was the same. It does not speed-up the application.