Hi Wim and Eugen,
On 11/22/2010 1:28 PM, Wim Jongman wrote:
Hi Eugen,
It is funny that this pops up frequently lately. I guess it
would be sweet if we could implement some kind of
ProgressMonitor while executing the task much like the progress
monitor in Eclipse.
In the mean time, you can implement your own progress service
OR use the ECF Future feature. You call a method async and you
get a Future back. You can poll the Future while you show an
"indefinite" progress (the one that sweeps) based on the status
of the Future.
Wim is quite right...this is a way to do progress monitoring on
consumer side of a remote service. Admittedly it isn't ideal,
however...as the client's progress indication doesn't actually get
data from the host/service side in order to show progress....rather
it just assumes some progress has been made because time passes.
By way of explanation...the real problem here is that normal/OSGi
remote method call doesn't support callbacks (and that's what
IProgressMonitor or custom equivalent is). The reason for this is
that it doesn't generally support remote method parameter
pass-by-reference...which is needed to trivially support callbacks.
With most providers remote method parameters are necessarily passed
by value (i.e. method parameters are serialized and a copy is sent
to the remote service host...rather than a distributed object
reference).
However, it's quite possible to define/create a messaging pattern to
implement progress monitoring...e.g. with the ECF shared object API
and/or the datashare API. This isn't strictly OSGi remote services,
though. Both ECF APIs can/could be pretty easily used to define the
messaging to support remote progress monitoring. One of the things
that I've contemplated doing is to add such a feature to
RegistrySharedObject (via the shared object api)...and perhaps even
to the remote services API...for example exposing it via a new type
of IFuture that would allow the specification of client-side
progress monitors that actually use server-side messages to update.
But, I haven't been able to personally work on this thread yet given
the attention of OSGi remote services. If folks would like to
persue adding such a feature then please open an enhancement request
and consider contributing or supporting work in that area.
Scott
