Using the Apache felix SCR Annoration @Reference in Scala, for an OSGI environment

Question

I am trying to use the @Reference Felix SCR annotation in Scala

This is how it can be used in Java:

public class Foo {

    @Reference
    MyServiceInterface service;
    // some code here
}

Here, MyService is ideally a Java Interface and not a concrete class (dependency injection)

I am using the same annotation in Scala, trying to depend on the same MyService (a Java Interface), like:

class Foo {
    @Reference
    val service = MyServiceInterface // ??
    // some code here
}

How can I use this annotation in Scala, to refer to a Java Interface?

example:

@Reference
val MyServiceInterface service

or

@Reference
val service = MyServiceInterface

is not valid Scala code

Thank you

Answer 1

I was able to solve this problem by specifying the type of the variable correctly like:

@Reference
var service: MyServiceInterface = null

@Neil is right, we must use a var instead of a val as the service binding happens at runtime.

Secondly, I had to add the following configuration to the maven-scr-plugin:

<configuration>
    <scanClasses>true</scanClasses>
</configuration>

Then, I had to specifically instruct the Maven Bundle plugin to NOT import the org.apache.felix.scr.annotations package as follows:

<Import-Package>!org.apache.felix.scr.annotations, *</Import-Package>

because the manifest would otherwise include an entry for this package as something that the bundle depends on.

Once this was done, the mvn-scr-plugin would generate the XML file correctly and the mvn-bundle-plugin would generate the bundle, manifest correctly.