Multiple interfaces and object by value
Nils Johansson
CORBA spec. supports multiple interfaces and passing objects by value.
The first one, multiple interfaces, I really dont understand, I'm really a
C++ programmer and you don't have interfaces in the same way you have in
JAVA for instance. Maybe this is the reason for my problem. How could the
same objet, that perform certain things, have different interfaces?
Second one probably means hat you can send objects as parameters, by their
value. What happens with the behaviour of the objects? Surely you can't send
methods encapsulated in objects to a remote invocated object, because they
might be on different platform and so on. Furtheron I thought that you only
more or less had primite types defined in IDL, not OO types.
Please enlighten me on these two topics, as I'm stuck even tho I tried to
figure
it out from the tons of Corba material availble on the net.
thanks,
Nils
Michi Henning
> I'm studying some articles, and they mention that the current version of
> CORBA spec. supports multiple interfaces and passing objects by value.
>
> The first one, multiple interfaces, I really dont understand, I'm really a
> C++ programmer and you don't have interfaces in the same way you have in
> JAVA for instance. Maybe this is the reason for my problem. How could the
> same objet, that perform certain things, have different interfaces?
OBV supports multiple inheritance, not multiple interfaces (in the sense
of COM).
> Second one probably means hat you can send objects as parameters, by their
> value. What happens with the behaviour of the objects? Surely you can't send
> methods encapsulated in objects to a remote invocated object, because they
> might be on different platform and so on. Furtheron I thought that you only
> more or less had primite types defined in IDL, not OO types.
Yes. There is no standard way for OBV objects to ship their code around.
For that reason, OBVs with methods don't fit all that well into the CORBA
architecture, unless you are using Java everywhere and can control the
client-side deployment environment.
> Please enlighten me on these two topics, as I'm stuck even tho I tried to
> figure
> it out from the tons of Corba material availble on the net.
Steve Vinoski has written an article that gives a good overview of OBV:
http://www.iona.com/hyplan/vinoski/cacm.pdf
There was also a discussion about this topic here recently that you may
find useful:
Cheers,
Michi.
--
Michi Henning +61 7 3324 9633
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Suite 4, 8 Martha St +61 7 3324 9799 (fax)
Camp Hill 4152 michi....@iona.com
Brisbane, AUSTRALIA http://www.ooc.com.au/staff/michi
Nils Johansson
> OBV supports multiple inheritance, not multiple interfaces (in the sense
> of COM).
Multiple Interfaces per Object, is what I had problems with, not
inheritance.
> There was also a discussion about this topic here recently that you may
> find useful:
>
>
http://groups.google.com/groups?hl=en&lr=&group=comp.object.corba&safe=off&i
c=1&th=db55861010dd9b80&seekd=937518451#937518451
>
Ill try to dig in, thanks
- Nils
Jacob
Michi Henning wrote:
>
> On Mon, 9 Apr 2001, Nils Johansson wrote:
>
> > I'm studying some articles, and they mention that the current version of
> > CORBA spec. supports multiple interfaces and passing objects by value.
> >
> > The first one, multiple interfaces, I really dont understand, I'm really a
> > C++ programmer and you don't have interfaces in the same way you have in
> > JAVA for instance. Maybe this is the reason for my problem. How could the
> > same objet, that perform certain things, have different interfaces?
>
> OBV supports multiple inheritance, not multiple interfaces (in the sense
> of COM).
It would be more precise to state that OBV multiple inheritance as
single inheritance from a stateful value type( with truncation ) and
multiple inheritance from stateless value types( abstract value types
).
single inheritance from a single interface.
multiple inheritance from abstract interfaces.
This sure sounds crazy. However, could you give a good reason other
than the Java to IDL mapping for the use of such complex features.
So long,
Jacob.
Michi Henning
> It would be more precise to state that OBV multiple inheritance as
>
> single inheritance from a stateful value type( with truncation ) and
> multiple inheritance from stateless value types( abstract value types
> ).
> single inheritance from a single interface.
> multiple inheritance from abstract interfaces.
>
> This sure sounds crazy. However, could you give a good reason other
> than the Java to IDL mapping for the use of such complex features.
Sorry, no. I can't really give a good reason for OBV either. What started
out as simple extensible structs turned into this rather complex thing
that people have a hard time understanding...