Eugen
BJ Hargrave wrote:
Note: This still requires that someone has called
Bundle.start(START_ACTIVATION_POLICY) on the bundle containing the DS
components. This only needs to be done once since the start state is
persistently recorded.
DS will always ignore bundles in the RESOLVED state.
--
BJ Hargrave
Senior Technical Staff Member, IBM
OSGi Fellow and CTO of the OSGi Alliance
[email protected]
office: +1 386 848 1781
mobile: +1 386 848 3788
From: Thomas Watson/Austin/i...@ibmus
To: OSGi Developer Mail List <[email protected]>
Date: 2009/04/30 11:40
Subject: Re: [osgi-dev] Certain service registration
Sent by: [email protected]
________________________________
Another option is to use Declarative Services and lazy activation.
The DS
implementation in Equinox supports lazy activated bundles. A lazy
activated
bundle can provide a service component while it is in the STARTING
(waiting
for first class load) state. Once the service component is used the
DS
runtime will load your service impl class and cause your bundle to
move to
the ACTIVE state.
Tom
<mime-attachment.gif>BJ Hargrave---04/30/2009 10:32:02 AM---I don't
know why
you have 2 bundles: service and serviceimpl. Normally one does that
to
decouple the bundle exporting the servi
<mime-attachment.gif>
From: <mime-attachment.gif>
BJ Hargrave/Austin/i...@ibmus
<mime-attachment.gif>
To: <mime-attachment.gif>
OSGi Developer Mail List <[email protected]>
<mime-attachment.gif>
Date: <mime-attachment.gif>
04/30/2009 10:32 AM
<mime-attachment.gif>
Subject: <mime-attachment.gif>
Re: [osgi-dev] Certain service registration
________________________________
I don't know why you have 2 bundles: service and serviceimpl.
Normally one
does that to decouple the bundle exporting the service interfaces
from the
bundle implementing the service. But you do that and then couple
the service
bundle to the serviceimpl bundle by having the service bundle start
the
serviceimpl bundle!
The simplest solution here seems to be: combine into one bundle and
make
that bundle use lazy activation. Then the first time one of the
service
interface classes is loaded, your activator will run and will
register the
service.
--
BJ Hargrave
Senior Technical Staff Member, IBM
OSGi Fellow and CTO of the OSGi Alliance
[email protected]
office: +1 386 848 1781
mobile: +1 386 848 3788
From: Eugen Reiswich <[email protected]>
To: OSGi Developer Mail List <[email protected]>
Date: 2009/04/30 11:07
Subject: Re: [osgi-dev] Certain service registration
Sent by: [email protected]
________________________________
Hi Neil,
you have exactly pointed out my problem with OSGi in RCP
applications!
I believe the solution is to use Declarative Services. In DS,
services
can be registered in the service registry before the actual
implementation object for the service is instantiated -- in fact,
this
is the default behaviour. A bundle offering services via DS still
need
to be activated, but now the activation is "free" because a
classloader does not need to be created for the bundle until the
service is actually used.
Is DS really the only way? I have downloaded Eclipse M6 and tested
the
DS-Editor. Well, how do I say it polite? If I have 2, 3 or even more
components in one bundle that require OSGi services I have to create
(if I got it right) 2, 3 or even more XML files with service-
component-
descriptions. This sounds like XML-hell.
To make this work in an Eclipse RCP environment, there are two
possible approaches. First, explicitly name the bundles offering
services in config.ini, and add the @start modifier. If you do not
know in advance the names of the bundles then you could have an
extender bundle which automatically starts any bundle with a
Service-Component header.
I can't use the config.ini as I really don't know the names of the
bundles in advance. That's why we start each serviceimpl bundle in
the
corresponding service bundle. But in case I do not want to use DS our
second solution was to start all bundles whose names end with
xxxx.serviceimpl in a dedicated startUp-bundle.
Kind regards,
Eugen
Am Apr 30, 2009 um 16:23 schrieb Neil Bartlett:
While I agree with Peter and Hal, I think the heart of your
problem is
the mismatch between the preferred lifecycles of bundles in Eclipse
environment vs the services-based approach.
In Eclipse (both the SDK and RCP apps), activation of bundles is
done
as late as possible. Lazy activation helps to ensure that Eclipse
starts quickly, and code implementing things like views and
buttons is
only loaded when the user actually shows an interest in those
things,
e.g. by clicking the button. The whole Eclipse extension registry is
set up to enable this by examining bundles when they are in the
RESOLVED state.
Services traditionally have a different lifecycle: they are
offered up
by a bundle before it knows whether any other component (or the
user)
actually wants them! So the bundle needs to be "eagerly"
activated...
but Eclipse strongly discourages this practice because bundle
activation has an up-front cost.
I believe the solution is to use Declarative Services. In DS,
services
can be registered in the service registry before the actual
implementation object for the service is instantiated -- in fact,
this
is the default behaviour. A bundle offering services via DS still
need
to be activated, but now the activation is "free" because a
classloader does not need to be created for the bundle until the
service is actually used.
To make this work in an Eclipse RCP environment, there are two
possible approaches. First, explicitly name the bundles offering
services in config.ini, and add the @start modifier. If you do not
know in advance the names of the bundles then you could have an
extender bundle which automatically starts any bundle with a
Service-Component header.
Regards,
Neil
On Thu, Apr 30, 2009 at 8:46 AM, Eugen Reiswich
<[email protected]> wrote:
Hi OSGi-devs,
I have the following problem with osgi services. We develop
basically
applications where dynamic is not an issue. So what I would like to
make
sure in my application is that all services are registred properly
at start
up - if not, the application will be shut down. In addition to that
I want
to reuse my bundles in RCP applications so any concept must also be
applicable for RCP applications.
Say I have two bundles:
1. org.mycompany.service (contains a service interface)
2. org.mycompany.serviceimpl (contains the service implementation
and
registers withing his activator an osgi-service)
What we do within the service bundle is this:
public void start(BundleContext context) throws Exception {
Bundle[] bundles = context.getBundles();
// find the implementation for the service bundle
for (Bundle bundle : bundles) {
if ("org.mycompany.serviceimpl".equals(bundle.getSymbolicName())) {
// service impl found
if (bundle.getState() != Bundle.ACTIVE) {
bundle.start();
}
}
}
// check if servicimpl has registred service properly
ServiceReference serviceReference = context
.getServiceReference(IMyService.class.getName());
if (serviceReference == null) {
// shut down application
}
...
From my point of view this is pretty error prone and difficult to
maintain.
Is there a best practice approach how I can make sure that all
services are
registered properly at start up of my application? How can I
start my
serviceimpl bundles in RCP application as no one depends on this
bundle
which is why the are never started?
We have spend now a lot of time to find solutions for this problem
but they
all seem to be improvable.
Regards,
Eugen
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