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From b..@petinou.fr
Subject Re: How to manage several service instances with declarative services?
Date Mon, 11 Jan 2016 17:56:20 GMT
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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