They represent classes, which is why I would have like to have a Class
annotation so I could do "tester=MyTester.class". instead of
"tester="com.acme.mypkg.MyTester".
For example I have a number of components implementing a service and as
part of their property they define their "filter conditions" which are then
passed on to the 3rd party library, and there are 2 types of testers, etc:
Component(service=ZKRenderer.class, factory=ZKRenderer.CONFIG_FACTORY,
property= { ZKRenderer.CONFIG_STATIC_TEST +
"=c.c.i.tester.ReferenceTree",
ZKRenderer.CONFIG_STATIC_TEST_PRIORITY + ":Integer=9" })
If I move my ReferenceTree tester in the above case, no compiler would
catch it and I'm just looking for pain in the future.
I am not sure I grasp your approach. Here clients just ask for a renderer
(an instance of the service) for some "object" that is passed in and an
appropriate and "highest ranking" one is returned. So the client is never
specifying the class string at all. Here we are providing the full class
name so it can be loaded, hence it would be much more natural to provide a
Class object.
When we have cases where the component and reference must have to match we
do as such:
public static final String CONFIG_QUALIFIER =
OsgiConstants.SERVICE_QUALIFIER + "=ReferenceList"; //$NON-NLS-1$
public static final String CONFIG_TARGET = "(" + CONFIG_QUALIFIER +
")"; //$NON-NLS-1$ //$NON-NLS-2$
and here the component use the 1st line in its property and the reference
target uses the 2nd constant and that is not an issue.
Alain
Alain Picard
Chief Strategy Officer
Castor Technologies Inc
o:514-360-7208
m:813-787-3424
[email protected]
www.castortech.com
On Fri, Aug 24, 2018 at 5:16 AM Tim Ward <[email protected]> wrote:
> Do these properties “represent” classes or are they actually classes? If
> they are just representations (which would be a good thing) then you can
> define a static string constant representing the class which is mapped
> internally to the correct class name (which can then change over time).
> Clients then filter based on the string representation which will not
> change.
>
> Tim
>
>
> On 24 Aug 2018, at 10:07, Alain Picard <[email protected]> wrote:
>
> Tim & all,
>
> My immediate use case is that my components have some properties and some
> of those represent classes (this interfaces with 3rd party libraries, I
> would probably design it differently if I could, but it has to be
> configuration as it is used to determine if the component is a match, much
> like for target filters). Properties in the component annotation are
> String[] and that forces the specification of classes as String which is
> very bad since if the class is moved, renamed, deleted, etc, it will cause
> no error or warning and blow up later on. And since annotations only
> support compile time constants, you can't do a MyClass.class.getName() to
> even get a String. My idea was since the implementation class is part of
> the component description, if I could get a hold of it, to have a static
> method in the class to provide this "constant".
>
> How can I work around the limitations of Properties as String and Java
> compile time constants. Am I stuck to introduce a new separate annotation
> to track this configuration?
>
> Alain
>
> Alain
>
>
> On Thu, Aug 23, 2018 at 5:24 AM Tim Ward <[email protected]> wrote:
>
>> The properties visible in the Map (or ServiceReference) are the service
>> properties. There is some overlap with configuration (services that are
>> configurable are encouraged to publish configuration properties as service
>> properties) but they are separate, and can be different.
>>
>> The only way that something becomes a service property is if it is
>> deliberately registered as such or, for a few specific properties such as
>> service.id and service.scope, added automatically by the framework.
>>
>> The class name of the implementation would only be added as a service
>> property if done so deliberately, and this is typically discouraged (it
>> leaks internal implementation detail and forces your internal naming to
>> become API). If you *really* care about the details of a service (and in
>> general you shouldn’t) then you should mark it with a service property that
>> you can recognise. Ideally one that is separate from the other
>> implementation details of the service.
>>
>> Best Regards,
>>
>> Tim
>>
>> > On 22 Aug 2018, at 16:53, Alain Picard via osgi-dev <
>> [email protected]> wrote:
>> >
>> > In a reference method, i can get the property configuration of the
>> service along with the ComponentFactory and some other optional arguments.
>> Can any of those give me a way to retrieve the implementation from the
>> configuration (i.e. the class name of the implementation) ?
>> >
>> > Thanks
>> > Alain
>> >
>> > _______________________________________________
>> > OSGi Developer Mail List
>> > [email protected]
>> > https://mail.osgi.org/mailman/listinfo/osgi-dev
>>
>>
>
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