When doing
query = session.createQuery("Select a.name,a.adress from myObject a");
List myList= query.list();

I will get a list of Obect[] objects, and not a list of myObject's.
Is there a way to make hibernate return a list of myObject , when I choose not to select all of the fields?

Or must I manually iterate over the list that is beeing returned, and re-create a list of myObject objects myself?

You could always try adding a constructor for myObject that takes those fields as parameters, and call:

query = session.createQuery("Select new myObject(a.name, a.adress) from myObject a");
List myList = query.list();

On the other hand, you should probably decide whether that fine a degree of lazy loading is really any more performant than just loading the whole object. Being able to specify Object and Collection associations (one-to-one, many-to-one and one-to-many) is usually sufficient for most cases.

Scott

In my case, I will use hibernate in cooperation with struts in a web.app.
The reason I do not want to select the whole objects is for different reasons:

In those cases where I need to return a list of objects, that list will be used in adminstration of objects, that means editing and deleting objects in the database. I only need things like name and description in order to create a list of this.
Some of the fields in the tables contain large amounts of text that I do not need in order to create a listing of available objects.
If I need to display a list of 10000 objects, it would take longer to query and return all fields/whole objects than just a few fields/parts of the object?

Another thing is that sometimes I need to write the whole List to session, and I would like to use as little resources as possible.

Your solution seems to work excellent, however I have a question:
I had an idea to create constructor that took all of properties available for this class.

Then I could set the un-needed propterties to "null" or "0", and I would not need to create one constructor for each "case".

I tried doing this:
session.createQuery("Select new myObject(a.name, a.adress,null,0) from myObject a");

It does not seem to understand "null" and "0", so what do I need to do in order to make this work?


Christian H.

As far as I know, HQL only supports selecting whole objects and object fields, not constants.

You could experiment with the use of createSQLQuery() to see if that works, but I don't know if it would.

It sounds like you want to support a situation where the fields to be loaded are dynamically specified (eg. by user preferences). In such a case, I wouldn't bother with the 'Select new ... ' pattern. Instead, just select the fields you want as you were before, step through the list of results and convert each Object[] into the object type you want. Do it within the data-access layer and it will all be transparent to other layers.

Scott