Re: ODMG Query over objects always returns a Collection (DList)?

[Robert S. Sfeir]

I should add that a DList or Collection of some type is returned is 
actually a good thing.  Why?  Take a scenario where you have a User 
object and we're returning a User object from OJB.  You use that object 
all over your code.  One day you decide to change the User object and 
call is People.  You code will be broken from top to bottom because it 
either won't find your object or you'll get ClassCastException s.  If 
we always return a Collection then you always deal with a Collection 
and what is inside it is irrelevant until you get to the point in your 
code where you need to retrieve that object.  In my case that doesn't 
happen until I get to the Presentation layer of my application which 
means I would effectively only break one spot if I changed anything, 
and that spot is predictable.

Just my 2c

On Monday, March 24, 2003, at 07:11 AM, Robert S. Sfeir wrote:

The Collection (DList which is changeable from the OJB.properties) 
DOES contain a User object.

On Friday, March 21, 2003, at 12:38 PM, Edson Carlos Ericksson Richter 
wrote:

Hi!

Table:
  UsersTable (id, username, password) -> mapped to User object with 
same
properties.
where id is Primary Key, and username is a unique key.

Well, if I query "select user from User where username = $1 and 
password =
$2", ODMG will always return a collection when I issue 
query.execute()? Or
it should detect that has only one object, and return a User object?

Just get from API doc for OQLQuery:
"The object that represents the result of the query. The returned 
data,
whatever its OQL type, is encapsulated into an object. For instance, 
when
OQL returns an integer, the result is put into an Integer object. 
When OQL
returns a collection (literal or object), the result is always a Java
collection object of the same kind (for instance, a DList). "

Appear to me that when OQL returns an User, the result should be put 
into
User object, as in "For instance, when OQL returns an integer, the 
result is
put into an Integer object".

Thanks for any clarification.

Edson Richter



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