Hi Jonathan,
Hmm.. I'd never thought of using PRO.narrow there. Never seen anyone else do
it either. Decided to do a little digging and it seems like the spec (1.1 at
least) is not entirely clear on this matter. The examples in sections 8.3.1
(calling create on home interface) and 8.3.2 (calling findByPrimaryKey) imply
that it is not required, since it is explicitly used in the example of 8.2.1
(acquiring the home interface) but not in the other two. The examples they
use are:
8.2.1
Context initialContext = new InitialContext();
AccountHome accountHome = (AccountHome) javax.rmi.PortableRemoteObject.narrow(
initialContext.lookup( java:comp/env/ejb/accounts ), AccountHome.class);
8.3.1
AccountHome accountHome = ...;
Account account = accountHome.create( John , Smith , 500.00);
8.3.2
AccountHome = ...;
Account account = accountHome.findByPrimaryKey( 100-3450-3333 );
So to me, these examples seem to make the case against using PRO.narrow on the
results of create/findBy*. In my mind this is quite logical, since these are
references provided specifically by the container as EJB remote interfaces,
whereas the result of lookup() is generic and thus required to be narrow()ed.
Surely the container should obviate the need for using PRO.narrow on
references that are specifically returned as EJB remote interfaces?
BUT then in section 8.9 they go and say
"A client program that is intended to be interoperable with all compliant EJB
Container implementations must use the
javax.rmi.PortableRemoteObject.narrow(...) method to perform type-narrowing of
the client-side representations of the home and remote interface."
contradicting their examples above.
Anyone else have any insight into this? If I'm missing something obvious here
please let me know!
-t
On Wed, Sep 06, 2000 at 01:51:48PM -0700, Jonathan K. Weedon wrote:
> Tony Abbott wrote:
> >
> > findBy methods on the home interface should return either the remote interface
> > or a Collection of remote interfaces. So just make findByParent return a
> > collection of categories. So your code would look something like...
> >
> > InitialContext context = new InitialContext();
> > Object obj = context.lookup("java:comp/env/ejb/Category");
> > CategoryHome ch = (CategoryHome)PortableRemoteObject.narrow(obj,
>CategoryHome.class);
> >
> > Collection col = ch.findByParent("Furniture");
> > Iterator i = col.iterator();
> > while (i.hasNext())
> > {
> > Category cat = (Category)i.next();
> > ... do stuff ...
> > }
> >
> > -t
>
> Tony,
>
> In the above code, you neglected to use PRO.narrow for the narrowing of
> the contents of the Iterator. It should be:
>
> Collection col = ch.findByParent("Furniture");
> Iterator i = col.iterator();
> while (i.hasNext()) {
> Category cat = (Category) PortableRemoteObject.narrow
> (i.next(), Category.class);
>
> }
>
> This is one of those insidious cases that I mentioned in a previous
> thread, whereby your version of the code would work in some AppServers,
> and not in others, even though (given your use of PRO.narrow for the
> JNDI lookup) you probably thought you were writing portable code.
>
> -jkw
>
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--
Tony Abbott [EMAIL PROTECTED]
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