API Criteria

ngijoi · **Joined:** Wed Aug 25, 2004 4:31 am **Posts:** 1

I would like to know how to retrive a specific column(for example the id column of the instance) using the method criteria.list()

Thanks for help
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stolley · **Posted:** Tue Oct 05, 2004 7:03 pm

Projection is not yet supported for the Criteria API, only HQL.

I believe it is expected sometime around the 3.1 timeframe (see the roadmap on the web site).

xcoulon · **Joined:** Thu Dec 18, 2003 4:13 am **Posts:** 19

Ok, but what about the ResultTransformer interface ? We heard about this feature but could not get much information ? Is it possible to use it in order to retrieve specific columns ?

Has anyone any code sample ?

Thank you in advance.

Xavier.

xcoulon · **Joined:** Thu Dec 18, 2003 4:13 am **Posts:** 19

I just found a way to use the ResultTransformer. Here is a sample of the class that implement this interface:

Code:

public class IDResultTransformer implements ResultTransformer {

  public Object transformTuple(Object[] tuple, String[] aliases) {
    Object object = tuple[tuple.length - 1];
    if(object instanceof MyEntityClass) {
      return ((MyEntityClass)object).getID();
    }
    return object;
  }

  public List transformList(List collection) {
    return collection;
  }

Then, instead of invoking the

Code:

criteria.list()

method, there just needs to call

Code:

criteria.setResultTransformer(new IDResultTransformer ()).list();

Xavier.

jeszy · **Joined:** Wed Nov 05, 2003 6:05 am **Posts:** 6

Hello,

Is it really possible to implement projection using the ResultTransformer API?

It seems to me that the properties of the objects passed to the transformTuple() method are not initialized except for the identifier properties.

In the above example this means that the property getter methods on the MyEntityClass instances other than the getID() return null.

After all, what is this interace good for?

Best regards,

Peter