Is it possible to inject a @reference object in a service with normal initialization? | Community
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vitis90
Level 3
July 17, 2017
Solved

Is it possible to inject a @reference object in a service with normal initialization?

  • July 17, 2017
  • 7 replies
  • 11675 views

Hi all,

Is it possible to initialize the object in class with @reference in a service with normal java initialization?

Example:

This is the class

public class AEMUtilImpl implements AEMUtil {  

    @Reference

    private ResourceResolverFactory resourceFactory;

    @Reference

    private SlingRepository slingRepository;

}

If I'm initializing this class in another class (like a servlet) like this:

AEMUtil aem = new AEMUtilImpl();

resourceFactory and slingRepository is always null.

If I initialize like this in a servlet

@Reference

AEMUtil aem;

resourceFactory and slingRepository do get initialized and works properly.

What is the reason behind this? Is there anyway we can initialize by using the first method?

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    Best answer by VeenaVikraman

    Hi

       As per Apache Felix documentation Apache Felix - SCR Annotations @Reference annotation is defined as below

         @reference is used to refer any service registered in your osgi console. So until you declare your class as a service , if you try to refer it using @reference annotation it is going to return you null.

    I would try to explain you in a plain language . One service can be referred only in another service.

    That means, if AEMUtilImpl is a service, then all the below objects will return you a valid object.


    So your code snippet should be something like below

    public interface AEMUtil {

    }

    @Service

    @Component(metatype = false)

    public class AEMUtilImpl implements AEMUtil {

    @Reference

        private ResourceResolverFactory resourceFactory;

        @Reference

        private SlingRepository slingRepository;

    }

    And in this case you should not initialize or cannot do the below

    This service should be initialized in any other service as below

    @Reference

    AEMUtil aemUtil;

    or in any Java class , you can use bundle context to get the object of the class as below

    servlets - Getting OSGi services from a bundle in Sling/CQ - Stack Overflow

    Hope this helps !! . Let me know if this is not what you are looking for .

    Thanks

    Veena

    7 replies

    smacdonald2008
    smacdonald2008
    Level 10
    July 17, 2017

    To use @Reference in a backend Java class - make sure you are using @Component and @Service annotations - see this article as an example --

    Adobe Experience Manager Help | Injecting a DataSourcePool Service into an Adobe Experience Manager OSGi bundle

    Hope this helps....

      viveksachdeva
      Community Advisor
      viveksachdevaCommunity Advisor
      Community Advisor
      July 18, 2017

      Your normal class is not registered in OSGi.. So you cannot use any of service in it... Even if you just use @Component annotation you can use other OSGi components in your class..

      V
      vitis90Author
      Level 3
      July 18, 2017

      No the servlet is registered. so is the service impl but when i do

      AEMService a = new AEMServiceImpl();

      all the instance variables inside the impl class is null.

      but when I do

      @Reference

      AEMService a

      the instance variables inside it like

      @Reference

      private ResourceResolverFactory resourceFactory;

      do get initalised. I was thinking if there was any work around to make first approach work

      zeeshanKhan0786
      zeeshanKhan0786
      Level 5
      July 18, 2017

      Hi Vitis,

      If  i am not wrong you are calling the class from Sling servlet if it is than you can do one thing.

      In the servlet you write

      public class Servlet extends SlingSafeMethodsServlet {   

      @Reference

      private ResourceResolverFactory resourceFactory;

      @Reference

          private SlingRepository slingRepository;

      //your code and call your class in doGet or doPost like yourClass y = new yourClass(resourceFactory,slingRepository);

      And these value in your normal class as constructur and assign these values in constructor.

      VeenaVikraman
      Community Advisor
      VeenaVikramanCommunity AdvisorAccepted solution
      Community Advisor
      July 18, 2017

      Hi

         As per Apache Felix documentation Apache Felix - SCR Annotations @Reference annotation is defined as below

           @reference is used to refer any service registered in your osgi console. So until you declare your class as a service , if you try to refer it using @reference annotation it is going to return you null.

      I would try to explain you in a plain language . One service can be referred only in another service.

      That means, if AEMUtilImpl is a service, then all the below objects will return you a valid object.


      So your code snippet should be something like below

      public interface AEMUtil {

      }

      @Service

      @Component(metatype = false)

      public class AEMUtilImpl implements AEMUtil {

      @Reference

          private ResourceResolverFactory resourceFactory;

          @Reference

          private SlingRepository slingRepository;

      }

      And in this case you should not initialize or cannot do the below

      This service should be initialized in any other service as below

      @Reference

      AEMUtil aemUtil;

      or in any Java class , you can use bundle context to get the object of the class as below

      servlets - Getting OSGi services from a bundle in Sling/CQ - Stack Overflow

      Hope this helps !! . Let me know if this is not what you are looking for .

      Thanks

      Veena

        Ratna_Kumar
        Ratna_Kumar
        Level 10
        July 18, 2017

        Awesome answer Veena_07​

        ~Ratna

          V
          vitis90Author
          Level 3
          August 7, 2017

          Thank you! This was very helpful.

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