Re: Using an interface between two dl'ed applications

Okay to make things clearer

System 'A' is a container of sorts, Object 'B' is a component that  
Object C (the caller) wishes to utilise and conenct with at runtime

Both the component and the caller are deployed into system A via a  
JINI service call (lets call it 'deploy()'), they are
deployed separately in two separate deploy() calls

The component 'B' implements an interface that the caller 'C' is aware  
of and has a compile time dependency on.

To call the component, the caller obtains the component through a call  
to the container. For the sake of security and transparency, the  
container returns a dynamic proxy (j.l.r.proxy) that implements the  
required interface (it extracts this interface from the full  
definition of the component 'B', before sending it back to the caller  
'C'.

The point that I'm making is that both 'B' and 'C' were created in  
separate calls, and potentially separate classloaders, meaning that  
the definition of the interface used by 'B' and that used by 'C' will  
be marked as being different because the class is not sourced from a  
the same single classloader when used/linked to by 'B' and 'C'

To be clear, this is not cross JVM as such - both B and C are in the  
same JVM, but are deployed via separate remote calls into the JVM....  
this can be of course solved by placing the interface on the classpath  
of the container, but this is not a desirable way for me to go

Calum


On 19 Jan 2009, at 13:33, Niclas Hedhman wrote:

> On Mon, Jan 19, 2009 at 11:55 AM, Calum Shaw-Mackay
> <[email protected]> wrote:
>> Given a system 'A' that allows objects 'B' and 'C' to be deployed  
>> to it,
>> where 'C' has an interface dependency on 'B'. Also 'B' and 'C" are
>> independently deployed, with potentially different codebases, but  
>> with the
>> same interface definition (compiled) in each.
>>
>> When 'C' requests access to 'B' via a dynamic proxy generated from  
>> the
>> Interface declared in 'B's codebase, I get a  
>> ClassNotFoundException, I'm
>> assuming that this is because B's classes are being declared in a  
>> different
>> classloader to 'C's.
>
> Are you talking a java.lang.reflect.Proxy, bytecode generated one or
> something else?
> I am not sure what you mean by "declared in different classloader to
> C's". Is it in the same JVM? Otherwise, why do you mention it? (I know
> you are not a novice... :-) )
>
> If we are talking j.l.r.Proxy, is the InvocationHandler in B
> serializable and its classes available to C? In JRMP, there is
> explicit support for j.l.r.Proxy since it is not straight forward. The
> Proxy from B should be reconstructed at JRMP level from the interface
> classes and invocationhandler instance received from B using the RMI
> Classloader in C for B's codebase.
>
>
> Cheers
> Niclas
> -- 
> http://www.qi4j.org - New Energy for Java

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