How to use ReportQuery to query against two types of objects?

Question

I have two loosely related classes Account and AccountState. They are not mapped to each other, have no inheritance or other relationships, but they both have account_id as their key attribute.
I would like to build a ReportQuery to return selective attributes across Account and AccountState. Is there anyway to do so?
Thanks in advance.
George Zou

Answer 1

George,
Typically for the scenario you are describing I would recommend adding a 1:1 relationship from Account to state using the shared PK. If this is an option you should note that to keep the ID napped in each as a direct-to-field you will need to set-up the 1:1 using a target foreign key.
For every 1:1 relationship in your model TopLink automatically creates a 1:1 query key. It is these query keys that you are implicitly using when defining expressions.
If you really don't want to add the 1:1 mapping to your model then you can alternatively add a 1:1 query key yourself to your Account class that allows for the relationship to be used in an expression and thus a Report Query.
Example 6-21 in the 9.0.4 application developers guide shows how to create a OneToOneQueryKey programmatically.
I would guess your descriptor after-load method would look something like:
public static void addToAccontDescriptor(Descriptor descriptor)
OneToOneQueryKey ownerQueryKey = new OneToOneQueryKey();
ownerQueryKey.setName("state");
ownerQueryKey.setReferenceClass(AccountState.class);
ExpressionBuilder builder = new ExpressionBuilder();
ownerQueryKey.setJoinCriteria(builder.getField("ACCOUNT.ID").equal(builder.getParameter("ACCOUNT_STATE.ID")));
descriptor.addQueryKey(ownerQueryKey);
Now whether you added the 1:1 mapping or the 1:1 query key the ReportQuery would look the same:
ReportQuery rq = new ReportQuery(Account.class, new ExpressionBuilder());
rq.addAttribute("id");
rq.addAttribute("State Value", rq.getExpressionBuilder().get("state").get("value"));
I hope this helps,
Doug