What are the minimum requirements to get a CXF (JAX-RS) Web Resource up and running in Felix?

Question

I'd like to get CXF, which implements JAX-RS, up and running in OSGI (specifically, Apache Karaf running Apache Felix).

Using this project: cxf-osgi-activator as an example, I see that the engineer made a design decision to split up the jetty Karaf feature from the jax-rs Karaf feature. Is there a dependency between the two at runtime? Does the jax-rs feature use some trick (from the environment: OSGI HTTP Service, for example) to get itself listening for inbound connections, or is that still needed? Maybe my question can be answered with an explanation of line 250 of the RestDeployer.java file. Where is it pulling its Server from exactly? Does it always get one, or does it have a dependency on the jetty Karaf feature?

I had a look at the tests, which seem to use iPojo or Declarative Services (hard for me to tell the difference!) to cut down on boiler plate code, but at the expense of understanding (because it requires more in-depth knowledge on the subject than I have at the moment it would seem.)

The official CXF documentation is less than desirable on this subject.

My understanding is that it boils down to having:

• a web resource file annotated with JAX-RS annotations to map inbound calls to local functions
• CXF runtime (some registration service that manages the lifecycle from reception of a call to return of serialized information)
• a server (Java Servlet or effectively an abstraction thereof that spawns threads for a given port) Purpose of cxf-rt-transports-http-jetty

How does this all play together in OSGI? I should also mention that am most familiar with Gradle, and the Maven pom.xml files likely contain things that I do not recognize.

I do not like the accepted answer to CXF web services with OSGI and Karaf, because it is specific to Blueprint, which I do not want to use because of its reliance on XML. I am looking for a technical answer here that explains the relationship between CXF and OSGI (like the OSGI HTTP Service).

Related:

• Apache CXF/JAX-RS, Felix and Jetty
• Purpose of cxf-rt-transports-http-jetty

Answer 1

Firstly, a tiny recap about OSGi :

1. OSGi is a specification that needs to be implemented
2. Felix/Equinox are the two implementations found in karaf (see your etc/config.properties, with the property karaf.framework to check the one you use, you can change it !)
3. Karaf is an administration tool that will use Felix/Equinox behind each command you make. Often, those commands are proxied to the corresponding behaviour defined by OSGi to the Felix/Equinox implementation.

So, the solution you linked with Blueprint is still true no matter your context. However, if you don't like Blueprint, you can either check Declarative Services where each "bean" you would have defined in a "spring/blueprint" world would become @Service/@Reference (more pure to OSGi original way of thinking) or use OSGI CDI Integration which will be way more intuitive if you are used to the more classic @Named/@Inject way of thinking inside a bundle.

But in the end, it's exactly the same principles : you want to have a Server running registering itself to the CXF Bus (which normally you shouldn't declare in your bundle, you can use the default one) and your Service registering itself in Server.