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From David Jencks <david_jen...@yahoo.com.INVALID>
Subject Re: How to manage several service instances with declarative services?
Date Mon, 11 Jan 2016 18:54:38 GMT
Well, you got farther anyway :-)  I don’t yet see what’s wrong.  Could you supply the generated
component xml and the ComponentException stack trace?

With bnd 3+ you don’t (shouldn’t?) need to specify (service=FileReader.class) as now bnd
can analyze the generic method/field signature to infer the service type.

thanks
david jencks
> On Jan 11, 2016, at 9:56 AM, ben@petinou.fr wrote:
> 
> Thanks David,
> 
> I tried that by get an error on karaf startup:
> cannot register Component org.osgi.service.component.ComponentException: Component FileReaderFactory
validation failed: Field value type must not be set for unary field references.
> 
> My class looks like this:
> 
> @Component
> public class FileReaderFactory implements ReaderManager {
>    @Reference(service = FileReader.class)
>    private List<FileReader> availableServices;
> 
>    @Override
>    public Data readFile(Path filePath) throws IOException {
>        for (FileReader reader : availableServices) {
>            if (reader.isFormatSupported(filePath)) {
>                return reader.readFile(filePath);
>            }
>        }
>        return null;
>    }
> 
>    @Override
>    public boolean isFormatSupported(Path filePath) throws IOException {
>        for (FileReader reader : availableServices) {
>            if (reader.isFormatSupported(filePath)) {
>                return true;
>            }
>        }
>        return false;
>    }
> }
> 
> Le 11.01.2016 18:47, David Jencks a écrit :
>> Well, you need cmpn 6 for the ds 1.3 annotations (in particular
>> @Reference applicable to a field).  I thought this was on maven
>> central but haven’t looked.  If necessary you can get it from the OSGI
>> site.
>> david jencks
>>> On Jan 11, 2016, at 12:35 AM, ben@petinou.fr wrote:
>>> Hi everyone!
>>> I asked a question on stackoverflow regarding the use of Declarative Services
in Karaf to manage multiple instances of a service, provided by different implementations
of such a service.
>>> The question is explained in details here:
>>> http://stackoverflow.com/questions/34706041/how-to-manage-several-service-instances-in-declarative-services
>>> I received and answer telling me that using the @reference annotation on the
list storing the services would solve my problem. For this, I would need to use DS 1.3.
>>> I thus asked on Karaf users mailing list what was the version of Felix SCR provided
with Karaf 4.0.3 (http://mail-archives.apache.org/mod_mbox/karaf-user/201601.mbox/%3C8dbfa59508d5769609e2c78c0210c7aa%40petinou.fr%3E)
and was told it was Felix SCR 2.0.2, which supports DS 1.3. So far so good.
>>> I was also kindly advised to ask this kind of questions here. So here I am :-)
>>> Following the answer on stackoverflow, I tried to add the @reference annotation
to my service list like this:
>>> @Reference(service = FileReader.class)
>>> private List<FileReader> availableServices = new ArrayList<>();
>>> But it does not compile: FileReaderFactory.java:[37,5] annotation type not applicable
to this kind of declaration
>>> My project has a dependency on:
>>> <dependency>
>>>   <groupId>org.osgi</groupId>
>>>   <artifactId>org.osgi.compendium</artifactId>
>>>   <version>5.0.0</version>
>>>   <scope>provided</scope>
>>> </dependency>
>>> which seems to be the latest version available.
>>> I thus tried the "older way" by using explicit bind/unbind methods like this:
>>>   @Reference(service = FileReader.class, unbind = "removeService")
>>>   public void addService(final FileReader serviceToAdd) {
>>>       System.out.println("FileReaderFactory.addService");
>>>       availableServices.add(serviceToAdd);
>>>       System.out.println(availableServices);
>>>   }
>>>   public void removeService(final FileReader serviceToRemove) {
>>>       System.out.println("FileReaderFactory.removeService");
>>>       availableServices.remove(serviceToRemove);
>>>       System.out.println(availableServices);
>>>   }
>>> If I have two implementations available, say TxtFileReader and XmlFileReader,
only the first one is added to the list. The status of the second service (using scr:detail
command) is "null".
>>> What am I missing?
>>> Kind regards,
>>> Ben


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