Hi,
I have some way to solve that problem. My question was for some
standardized way which to be common practice.
My scenario is when I have one bundle it is not possible everything to
be in the Activator and Service(s) implementation. In most of the cases
we need of some helper classes which needs to use another services from
another bundles. This is the problem that I would like to solve in
simple way, not so difficulty how is solved with Guice & Peaberry. Guice
& Peaberry solve that problem but when we have a chain of services and
classes it is very hard to do initial initialization. In the same way
this can be done very simple if they are part of the OSGi Framework
implementation.
Miro.
Richard S. Hall wrote:
Miroslav Nachev wrote:
Hello Clement,
In traditional way if I have some OSGi Service which have to be used
in some class (POJO Bean) I MUST pass this service to one or more
classes as parameter. Then when the time for using of that service is
on the service can be unavailable. Similar problem I will have when I
want to stop my bundle. That's why if iPOJO Annotations allow some
service to be used inside of the bundle will be perfect. This can be
done with Proxy. When I create some new object with new
JavaClass(...) and in that object I am declared some OSGi Service
using iPOJO Annotation, that service will point to some Proxy which
proxy will try to get the service on request. This will guarantee
that the service is actual independently how much the service is
restarted and updated. In traditional way the application must track
all service states and etc. Passing the service as parameter
complicate the things.
Did you have some plans iPOJO to support the above scenario?
I am not totally sure I understand your scenario, but it sounds like
you want a proxy that only tries to get the service when someone tries
to use it. iPOJO does not support this type of scenario automatically,
but it is fairly easy to achieve. Assume you have the following service:
public interface Foo {
void doFoo();
}
You could create a component like this:
import org.apache.felix.ipojo.temporal.Requires;
public class MyFooProxy implements Foo {
@Requires
private Foo m_foo;
public void doFoo() {
m_foo.doFoo();
}
}
The dependency on m_foo is declared to be temporal, which means that
it will only try to get the service when it is used. If one is not
available, it will eventually timeout and throw an exception. Now you
should be able to pass this "proxy" component to you components and
they will be able to use the service on demand.
-> richard
Regards,
Miro.
clement escoffier wrote:
2008/10/14 Stuart McCulloch <[EMAIL PROTECTED]>
2008/10/14 Miroslav Nachev <[EMAIL PROTECTED]>
Hi,
This is very interesting and I will try it but this answer is half
of my
question. I am interesting how to get some service in my code, not in
another service. For example:
public class SomePOJOBean
{
@Requires
??? how to pass some parameters to the service (passive, dynamics)
private FooService foo;
}
How can be implemented the above scenario?
So, as I understand, you don't want (global) services but your own
(customized) service. As you're configuring the service, this
service should
not be available to other consumers. In iPOJO you can do this by using
composites (the new documentation is coming soon). Composites assert
that
your service is isolated. However, composites does not allows you to
declare
those services in your code.
Well, iPOJO injects components - but these are not necessarily
services.
Clement's example happened to provide a service, but this isn't
mandatory.
You do need to tell iPOJO about your code somehow, and in iPOJO
this is
done
by marking them as components which iPOJO injects as necessary.
(I'm sure
Clement can explain this better than me!)
Service providing is (of course) not necessary. Your component can be a
component that does not provide a service (like a GUI).
Clement
There are also alternative ways to inject OSGi services, using
(non-OSGi)
dependency injection frameworks:
* Spring has the Spring-DM extension, but I don't know if it fully
supports
configuration via annotation.
http://www.springframework.org/osgi/
* Guice has the peaberry extension, which I work on - in this case
the
service configuration is done in the binding module, not the
annotation (I
did look at doing annotation configuration, but this rapidly becomes a
management nightmare)
http://code.google.com/p/peaberry/
HTH
Regards,
Miro.
clement escoffier wrote:
Hi,
iPOJO provides such annotations as:
@Component
@Provides // Provides a service
public class Foo implements Service {
@Requires // Service dependency
private HelloService hello;
...
}
You can find further info at
http://felix.apache.org/site/how-to-use-ipojo-annotations.html
About parameters, the iPOJO's way is to inject instance property.
Those
fields will be set before the execution of your constructor
(between the
super constructor invocation and the constructor code), and your
constructor
can use those fields, such as in:
@Component
@Provides // Provides a service
public class Foo implements Service {
@Property
private String myString;
@Requires // Service dependency
private HelloService hello;
public Foo() {
// Can use myString here as well as hello
}
...
}
Regards,
Clement
2008/10/14 Miroslav Nachev <[EMAIL PROTECTED]>
Hi,
I would like to ask you about some way in Felix to export
services in
more
easy way only with annotation like in EJB3.x: @Stateful,
@Stateless,
@Remote, @Local, @EJB, etc.
In my opinion the best way this to be done is inside of the OSGi
framework.
Then all resources (services) can be exported to the framework just
with
annotation. The same for needed services. What about if before
to get
some
service we have to pass some parameters to the constructor?
Regards,
Miro.
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