Tony,
The basic rule of thumb is that a PRO.narrow is needed wherever
a Java cast is needed. Elsewhere, it is not needed.
Specifically, a PRO.narrow IS NOT needed for:
* create methods
* single object finders (including findByPrimaryKey)
(and you will note a Java cast is also not required).
However, a PRO.narrow is needed for:
* JNDI lookups,
* multi-object finders (including your findByParent)
(and you will note that a Java cast is required).
The spec is completly consistent on this matter.
-jkw
Tony Abbott wrote:
>
> 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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