EJBQL, MIN and java.sql.Timestamp

Question

I am trying to create a new finder method for a cmp bean which returns me the date of the oldest bean available.
the ejbql query looks like this:
select MIN (a.receiveDate) from AssetSchema as a
receiveDate is defined as a java.sql.Timestamp field in the bean. I am getting the following error:
Bean: Asset
Method: clover.AssetLocal findOldestDeleted()
EJBQL: select MIN (a.receiveDate) from AssetSchema as a
Error: JDO75334: Invalid type 'java.sql.Timestamp' of select clause expression for finder method.
anything wrong with the query or .....

Answer 1

Instead of using a finder, use an ejbSelect method. You can then use the aggregate function MIN. Wrap the ejbSelect in a home method.
In remote Home interface, define home method:
public java.lang.String selectMinSingle() throws RemoteException;
define the ejbSelect method in EJB class:
public abstract java.lang.String ejbSelectMinSingle() throws FinderException;
The ejbSelect is wrapped in a ejbHome method:
public java.lang.String ejbHomeSelectMinSingle()
try {
String s = ejbSelectMinSingle();
return s;
} catch(Exception e) {
throw new EJBException("ejbHomeSelectMinSingle: " + e);
Call home method from client:
String s1 = beanHome.selectMinSingle();
Not sure if this is what you're looking to do.
There is also the ORDER BY clause; i.e.,
<ejb-ql>Select p.quantity from ProductBean p ORDER BY p.quantity</ejb-ql>
use the ASC or DESC keyword:
<ejb-ql>Select p.quantity from ProductBean p ORDER BY p.quantity ASC</ejb-ql>
For finder:
query>
<description></description>
<query-method>
<method-name>findProductsByHighestQuantity</method-name>
<method-params />
</query-method>
<ejb-ql>Select DISTINCT OBJECT(p) From ProductBean p ORDER BY p.quantity DESC</ejb-ql>