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From Jean-Baptiste Onofré ...@nanthrax.net>
Subject Re: [DISCUSSION] Karaf Boot
Date Wed, 09 Sep 2015 19:52:20 GMT
After a quick chat with Achim, it would be also possible to extend the 
support of annotations to spring and cdi annotations, and generate the 
corresponding artifact. But, anyway, the key turn artifact generation 
has value IMHO.

Regards
JB

On 09/09/2015 04:32 PM, Jean-Baptiste Onofré wrote:
> Hi all,
>
> I worked on a prototype about Karaf Boot.
>
> Let me give you some backgrounds and discuss about that all together.
>
>   Why Karaf Boot ?
>   ----------------
> When you develop artifacts (bundles) to be deployed in Karaf, you can
> see that the actual time that you spend on your business code is finally
> largely less important that all the plumbing effort that you have to do
> (writing OSGi Activator, or blueprint/scr descriptor, etc).
>
> It means that your "go to market" is longer, and we should provide
> something that allows you to focus on your code.
>
> Even if SCR annotations is a very good step forward, some use cases are
> not so easy to do (JPA, JTA for instance).
>
> And anyway, you have to prepare your pom.xml with different plugin and
> dependency.
>
> Moreover, when you have your artifacts, you have to prepare Karaf
> container, and deploy those artifacts there. Even if it's "container"
> approach is the most important for me, we can give even more flexibility
> by providing a way to embed and prepare Karaf in a ready to execute
> jar/artifact.
>
>   What is Karaf Boot ?
>   --------------------
> Karaf Boot provides four components:
> * karaf-boot-parent is the Maven parent pom that your project just
> inherit: that's all ! All plugins, dependencies, etc are described in
> this parent, you even don't have to define packaging as bundle, standard
> jar is fine.
> * karaf-boot (coming with karaf-boot-parent) provides annotations that
> you use directly in your business code (like @Bean, @Service,
> @Reference, @Inject, etc): again, your focus on your code, karaf-boot
> deals with the plumbing.
> * karaf-boot-maven-plugin (coming with karaf-boot-parent) scan the
> classes and generate a blueprint XML. For now, I'm using blueprint
> generation (because we can cover lot of use cases, for instance, I plan
> to provide @rest annotation that will generate blueprint XML with cxf
> jaxrs server, etc).
> * karaf-boot-starter is the module providing a convenient way to embed,
> configure and bootstrap Karaf.
>
> Just to illustrate this, let's take a look on the karaf-boot-sample-simple.
>
> The pom.xml is really simple:
>
> <?xml version="1.0" encoding="UTF-8"?>
> <project xmlns="http://maven.apache.org/POM/4.0.0"
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
> xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
> http://maven.apache.org/xsd/maven-4.0.0.xsd">
>
>      <modelVersion>4.0.0</modelVersion>
>
>      <parent>
>          <groupId>org.apache.karaf.boot</groupId>
>          <artifactId>karaf-boot-parent</artifactId>
>          <version>1.0.0-SNAPSHOT</version>
>      </parent>
>
>      <artifactId>karaf-boot-sample-simple</artifactId>
>      <version>1.0.0-SNAPSHOT</version>
>
> </project>
>
> You can see, the only thing that the developer has to do: define
> karaf-boot-parent as parent pom. That's all.
>
> Now, in the code, you have just one bean that we want to run:
>
> package org.apache.karaf.boot.sample.simple;
>
> import org.apache.karaf.boot.Bean;
> import org.apache.karaf.boot.Init;
>
> @Bean(id = "simple-bean")
> public class SimpleBean {
>
>      @Init
>      public void simple() {
>          System.out.println("Hello world");
>      }
>
> }
>
> You can see the @Bean and @Init karaf-boot annotations. The
> karaf-boot-maven-plugin will generate the blueprint descriptor using this.
>
>
>   Current Status
>   --------------
> I pushed Karaf Boot structure there:
>
> https://github.com/jbonofre/karaf-boot
>
> It's a mix of rewrapping of existing code (from aries, pax-exam, etc)
> and additions.
>
> I created the annotations, I'm now working on the
> karaf-boot-maven-plugin based on Christian's work in aries (I'm actually
> scanning the boot annotations now, and generating the XML).
>
> I will push new changes later today and tomorrow.
>
>   Open Questions
>   ---------------
> * For now, I would prefer to be 'artifacts' and 'resources' generator: I
> think it's better than to depend to a feature running in Karaf, but it's
> open to discussion.
> * I'm now generating blueprint. Probably native OSGi or scr generation
> can make sense.
> * I'm generating bundles: thanks to the Karaf4 features resolver, as the
> bundles provide requirements/capabilities metadata, I think it's a good
> start. However, maybe it's worth to be able to create features, kar,
> profile.
>
> Thoughts ?
>
> Thanks,
> Regards
> JB

-- 
Jean-Baptiste Onofré
jbonofre@apache.org
http://blog.nanthrax.net
Talend - http://www.talend.com

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