[forge-dev] reflection to access classes in project dependencies

[John Franey]

Thomas,

I have minimal exposure to proxy due to experience with hibernate, but my
understanding is not adequate to understand how they would apply.  Do I
understand correctly that the benefit of a dynamic proxy is high when a
temporary class implementation is needed, and when a method of the proxy is
invoked, some action is taken, perhaps instantiating another implementation
of the interface.  In this use case, we don't need to invoke the methods of
a project's class, we need to inspect the methods (and other members) of
the class, right?

John




On Thu, Feb 14, 2013 at 11:22 AM, Thomas Frühbeck <fruehbeck at aon.at> wrote:

>  exactly what I was looking for :-))
> Thanks George!
>
> Am 14.02.2013 16:55, schrieb George Gastaldi:
>
> Hi Thomas,
>
>  Have a look in Forge 2.0 source code. We're using javassist at it's best
> in the proxy module
>
>
>
> Em 14/02/2013, às 13:53, Thomas Frühbeck <fruehbeck at aon.at> escreveu:
>
>   Hi John,
>
> my two cents:
>     - this feature is a must-have, if Forge should be more than a tool to
> iniitialize projects, really great idea
>     - being pragmatic I would say this calls for proxy classes, similar to
> CDI decorators or the copy-on-write strategy
>
> (AFAIK the downside to CDI decorators is that they need interfaces on the
> base classes, thus again requiring changes of the classes if they hadnt
> been designed for it firstplace.)
>
> I have a very similar problem I am currently trying to solve with silly
> wrapper classes and was starting to think about dynamic proxy generation -
> unfortunately I have _no_ experience with such technology other than being
> simple user :-/
>
> Have you thought about javassist? Is it an option at all?
>
> Thomas
>
>
> Am 14.02.2013 16:21, schrieb John Franey:
>
> My motivation for this email is to satisfy FORGE-773.  However, this is
> also related to FORGE-563 and FORGE-424, and resolution could enable other
> features.
>
>  I have written a prototype:
> 1) an implementation of the forge java api interfaces which delegates to
> java's reflection, offering a read only perspective of java components.
> 2) a forge module, currently a facet, to search for a given binary class
> in the project's dependencies and returns the result wrapped in the above
> delegate.
>
>  These are demonstrable in a unit test.
>
>  My dilemma now is how to integrate these into the forge project.  There
> are a few different areas, but I'll start with this:
>
>
>  For some callers, a java class is a java class, whether it originates as
> source code (from the current forge project) or is a class from the
> dependency set.  For example, scaffolding primarily is a read only
> operation.  In this use case, it would be simpler for these clients to have
> a single interface to resolve classes because whether a class is source or
> binary is not relevant to the use case.
>
>  On the other hand, there is a set of classes in a user's project that
> are modifiable.  In these cases, a java class is not a java class.  Forge
> components might want the distinction somehow.  There ought the be some
> distinction of which class is modifiable and which is not.
>
>  Naively, I took the first thinking that the existing forge java model
> would be adequate.  To have separate java api for read-only and read-write
> java model objects seems a fundamental addition to the java model which
> requires much more effort.  In absence of such a model, I though to
> implement 'no-op' for those code changing methods  (e.g., Named.setName()
> would be inert).  I assumed that forge component that change source code
> would have necessary context to know when it is operating on a source code
> module, avoiding attempts to modify a binary class.
>
>  So, I'm looking for discussion and consensus on the above.  Any thoughts?
>
>  Regards,
> John
>
>
>
>
>
>
>
>
>
>
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