Re: Understanding getResultList()

[Craig L Russell]

Hi David,

On Jan 21, 2008, at 3:34 PM, David Beer wrote:

Hi All

I have a n issue with using Query getResultList(), I am executing a nativeQuery("SELECT * FROM ENTRY", Entry.class). And performing the query like so List<Entry> results = (List<Entry>)query.getResultList(); and in return I am seeing a list containing a delegate and a persistence object. My main problem is that I am trying to display the resulting data that comes back in a JList, in order to set the list data on a JList you have to have the data in a Vector. So when I tried to cast the List to a Vector I got an exception.

JList(ListModel dataModel)




Object getElementAt(int index)
          Returns the value at the specified index.

JList myJList = new JList( new MyListModel (listReturnedFromQuery));

class MyListModel{
List myList;
MyListModel(List underlying) {myList = underlying;}

Object getElementAt(int index) {return myList.get(index);}
int getSize() {return myList.size();}
}

Craig

You might be better off creating a trivial implementation of a ListModel instead of using Vector (which is so last year). Constructs a JList that displays elements from the specified, non-null, model. Since there is no change possible to the underlying List, you just need to implement the getElementAt method and delegate to the underlying List. void addListDataListener(ListDataListener l) {throw NotImplementedException;} void removeListDataListener(ListDataListener l) {throw NotImplementedException;}

When I perform the same query using TopLink I get back a list of Objects of the type and no extra information. At the moment I am going through the results and getting each Object element and adding to Vector to display. This is fine with a small amount of records but what about a large amount of records.

Creating your own ListModel will also address this issue.

Craig

Thanks

David

What is the best way of getting back just a list of Objects no additional data?

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

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