[forge-dev] OSGi prototype

Lincoln Baxter, III lincolnbaxter at gmail.com
Tue Oct 16 14:05:10 EDT 2012

Having trouble getting JDK 1.7.0 on my machine... did you use 1.7 or will
1.6 suffice?


On Mon, Oct 15, 2012 at 3:35 PM, Paul Bakker <paul.bakker.nl at gmail.com>wrote:

> THE zip contains a eclipse plugin site. Configure it as such in the
> eclipse install wizard.
> Sent from my iPhone
> On 15 okt. 2012, at 21:01, "Lincoln Baxter, III" <lincolnbaxter at gmail.com>
> wrote:
> How do you install BNDTools 2.0 once you have downloaded and extracted the
> archive.zip latest build from the CI server?
> Thanks,
> ~Lincoln
> On Sat, Oct 13, 2012 at 4:17 PM, Paul Bakker <paul.bakker.nl at gmail.com>wrote:
>> Hi all,
>> As discussed in last Wednesday meeting I created a basic OSGi based
>> prototype for Forge 2.0. This is not even close to a port of Forge, but
>> rather a demonstration on how the basic programming model could work for
>> further discussion.
>> The prototype contains the following:
>> 1) A jline shell that can execute plugins
>> 2) A plugin example using Felix Dependency Manager
>> 3) A plugin using SCR annotations
>> 4) A simple Facet that can be injected
>> Note that jline is not configured properly, I didn't really look into
>> that.
>> Plugins are OSGi services, so they need to be registered to the service
>> registry. This can be done using any dependency injection framework in
>> OSGi, for the example I have focussed on Felix Dependency Manager and
>> Declarative Services with annotations.
>> A plugin doesn't need to be annotated and doesn't need to implement any
>> interfaces. The only requirement is a service property "plugin" that
>> defines the name (alias) of the plugin. Service properties are a standard
>> OSGi services feature.
>> The Forge shell listens to plugin registrations and de-registrations.
>> Whenever a new plugin service is registered to the service registry it will
>> be picked up, and whenever a service is unregistered it will be removed
>> from the list of services. This is very valuable for adding/(re)installing
>> new plugins while running Forge. While this is kind of hacky in the current
>> Forge implementation, this is one of the very basic features of OSGi
>> services. The fact that it only requires a few lines of code sort of proves
>> that :-)
>> Another important part of Forge are Facets and dependency injection of
>> Facets. Facets are also OSGi services, but in this case they should publish
>> an interface (that's the whole idea of Facets). In the prototype there is a
>> Project interface defined in the exported api package. This interface is
>> implemented and published as a service by the ProjectFacet project. Again
>> I'm using Felix Dependency Manager to register the service, but we could
>> use annotations as well. The Project facet is then injected into the
>> ExamplePlugin (using Felix DM again).
>> The programming model for Plugin developers is very similar to the
>> current model. You define a pojo and register it to the registry using
>> either an annotation or an Activator. Because we package plugins as OSGi
>> bundles we do need a manifest. When using BndTools this is all generated
>> automatically, you don't even have to know it's there. When using Maven you
>> can use the Maven Bundle Plugin, which is also based on Bnd and does
>> basically the same. As a plugin developer you just add the plugin to the
>> POM (or Forge does that for you, I already have a plugin for that...) and
>> that's it. No need to worry about import/exports or anything else OSGi
>> related. Packaging a plugin could be done in several ways (from code,
>> picking up from disk etc.). Basically you just need to install the bundle
>> into the OSGi framework.
>> As a core developer the model is very similar too. Basically you still
>> just develop internal plugins and facets the same way you would today. We
>> can be more strict about interfaces and versioning however. Public
>> classes/interfaces must be explicitly export in the Manifest. This is a
>> good thing! It's impossible to use non-exported packages in OSGi, so we can
>> strictly enforce that plugins only use public APIs. Exported packages are
>> also versioned. A client of a class/interface will usually import the
>> package using a version range up to the next major version for example.
>> Using this you can have semantic versioning, and compatibility problems
>> will be more predictable.
>> This prototype just shows the very basic model. If we agree this is a
>> good model to move forward with, we should look at some more detailed
>> requirements such as plugin sharing/inheritance and library usage. Before
>> hacking away we should probably come up with some requirements for that :-)
>> Running the prototype:
>> The code is on github: https://github.com/paulbakker/forgeosgi.
>> Note that you need BndTools 2.0 to play with the code. This is an Eclipse
>> plugin that does all the OSGi related stuff. BndTools 2.0 is not released
>> yet (but I'm using it daily) and you can get it from the latest build:
>> https://bndtools.ci.cloudbees.com/job/bndtools.master/lastSuccessfulBuild/artifact/
>> .
>> After installing BndTools you can create a workspace and import the
>> projects. You can run from Eclipse by opening org.jboss.forge.shell,
>> right-click on forge.bndrun and select "Run as->OSGi run". This runs Forge
>> in an Eclipse console which is not very useful because it messes up the
>> shell. It does give you hot code replacement however. Packaging Forge is as
>> simple as opening the bndrun file, go to the run tab, and click export. You
>> get a executable jar file that contains everything. Hot code replacement in
>> a Forge instance running in a normal terminal should also be possible, but
>> we have to do some work for that (normally you would just use the Eclipse
>> console). The two plugins both support a "setup" command and can be
>> executed as "example setup" and "annotated setup".
>> Cheers,
>> Paul
>> _______________________________________________
>> forge-dev mailing list
>> forge-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/forge-dev
> --
> Lincoln Baxter, III
> http://ocpsoft.org
> "Simpler is better."
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Lincoln Baxter, III
"Simpler is better."
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