Hi Guillaume,
thanks for your feedback.
I fully agree about providing more high level annotations (it's what I
do with @jpa, @rest, @soap, @jta annotations).
I agree that the current annotations are too low level, and blueprint
"oriented". I just move forward a bit with the current codebase, just to
illustrate karaf-boot usage in the samples.
But again, you are right, and I will create a new annotations set.
One of the purpose of karaf-boot annotations is to "abstract" the actual
code/artifact that we generate. So, if now we generate blueprint,
without changing the karaf-boot annotations, we will be able to generate
something else (why not SCR, etc).
I agree with a BOM, but I think it's interesting to provide both:
- providing a ready to use parent pom allows developers to create a very
simple pom.xml where all plugins and dependencies are already defined
- for more advanced devs, they can create their own pom.xml starting
from the BOM or archetype.
Thanks again for your feedback !
Regards
JB
On 09/10/2015 04:44 PM, Guillaume Nodet wrote:
I like the idea.
For the annotations, we need to keep really high level. The annotations in
the code base right now are much too close to blueprint.
I think we need to grab a small enough subset so that the annotations are
easy to understand for beginners and without any ambiguities, even at the
cost of features.
For example, I think we should restrict to constructor injection, so that
we don't have any bind / rebind / init methods. We simply need an optional
@Destroy. In case the dependencies change at runtime, simply destroy the
bean / service and recreate it the dependencies are still met after the
change.
If blueprint is to be hidden completely, we may find a better alternative
in SCR or even Felix Dependency Manager, but it does not matter too much
for now.
I agree with the idea of using a BOM instead of a parent if possible. I'm
not very familiar, but this is less invasive.
The real problems will come with the support of higher level annotations
for JAXRS, JPA, etc...
Not really sure how to handle those yet...
2015-09-09 16:32 GMT+02:00 Jean-Baptiste Onofré <[email protected]>:
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
[email protected]
http://blog.nanthrax.net
Talend - http://www.talend.com
--
Jean-Baptiste Onofré
[email protected]
http://blog.nanthrax.net
Talend - http://www.talend.com
