RE: [platform-core-dev] Can I use Eclipse Platform Core functionalityout

[Jeff McAffer <Jeff_McAffer@xxxxxxxxxx>]

This is where it is a bit tricky.  Sitting
outside the Eclipse infrastructure is not a happy place.  When you
start up Eclipse you have to give it an "application" to run.
 Think of this like the traditional Java main().  EclipseStarter
sets up all the classloaders etc and then runs your application (see IPlatformRunnable).
>From then on Eclipse is control.  If the application exits then Eclipse
exits.  So in this scenario Eclipse wants to be in control.  This
is one of the reasons I suggested you might want to strip out the Extension
registry.

Beyond that, you can get the various
classloaders by grovelling around in the OSGi implementation using reflection
but that's not alot of fun.

Jeff

"Kai Shen" <kshen@xxxxxxxxxxx>
Sent by: platform-core-dev-bounces@xxxxxxxxxxx

04/12/2005 09:06 PM

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Subject	RE: [platform-core-dev] Can I use Eclipse Platform Core        functionalityoutside Eclipse?

Jeff,
 
Thank you very much for
the comment. I appreciate it a lot! I'll follow the track and try it out.

 
Right now, I have a specific
question regarding this approach. I guess EclipseStarter will use a separate
classloader to load the platform. If so, how can I get the classloader
in my Java application? I think the main Java application can only access
the Eclipse platform and runtime functions through that classloader. Is
it the only way to do it?
 
Thanks,
Kai

---

From: platform-core-dev-bounces@xxxxxxxxxxx
[mailto:platform-core-dev-bounces@xxxxxxxxxxx] On Behalf Of Jeff
McAffer
Sent: Tuesday, April 12, 2005 5:24 PM
To: Eclipse Platform Core component developers list.
Subject: Re: [platform-core-dev] Can I use Eclipse Platform Core functionalityoutside
Eclipse?


Kai, 

Sure, I know of several people who are doing this already.  Keep in
mind that OSGi was originally designed for embedded applications to it
is eminently suited to this task.  The runtime is not particularly
special.  The entry points on EclipseStarter are there precisely so
you can start Eclipse from another Java program so you are on the right
track. 

Note that you can also consider using the extension registry by itself.
 The registry has very little dependency on OSGi.  If you look
carefully through the code you will see only a half handful of references
to OSGi API (primarliy in ConfigurationElement).  you could strip
the extension registry code out of the runtime plugin and tweak to suit
your needs.  We actually wanted to do this in 3.1 but ran out of time.
 Perhaps you could contribute some ideas? 

Someone mentioned issues with allowing other plugins to be installed as
being a problem for the use of Eclipse on the server.  This would
be a problem anywhere then I guess.  Eclipse (OSGi and the Runtime)
to not enable people to just install plugins as they choose.  Some
agent always has to install plugins.  There is one call in particular
(BundleContext.installBundle) that does the work.  If no one calls
that, nothing will be installed.  So, you can setup any system (server,
desktop, ...) to be locked down simply by not making that function available.

Jeff

"Kai Shen" <kshen@xxxxxxxxxxx>
Sent by: platform-core-dev-bounces@xxxxxxxxxxx

04/12/2005 07:16 PM

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"Eclipse Platform Core component developers list."

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cc	Kai Shen <kshen@xxxxxxxxxxx>
Subject	[platform-core-dev] Can I use Eclipse Platform Core functionality        outside Eclipse?

Hi, 
  
We're working on a server side project. In this project, we'd like to provide
user an extension framework so that user can use Eclipse's extension mechanism
in server side. Our goal is to allow user to develop their plug-ins in
Eclipse environment and use those plug-ins directly in server side without
any modification. 
  
I understand Eclipse use org.eclipse.osgi and org.eclipse.core.runtime
to manage the bundles, classloaders and extension registry, etc. So, ideally,
we can use org.eclipse.osgi and org.eclipse.core.runtime
in our java application. 
  
However, I found the following in the Eclipse on-line help:
The Eclipse Platform makes heavy use of Java class loaders for loading
plug-ins. Even the Eclipse Runtime itself and the OSGi framework need to
be loaded by special class loaders. Client programs, such as a Java main
program or a servlet, cannot directly reference any part of Eclipse directly.
Instead, a client must use the EclipseStarter class in org.eclipse.core.runtime.adaptor
to start the platform, invoking functionality defined in plug-ins, and
shutting down the platform when done. 
Clients that do not need to access any particular function, but just need
to start the platform, can use Main.run() in startup.jar. However, clients
that need to invoke specific function should use EclipseStarter. See the
javadoc inside this class for details. 
  
It looks like we can NOT use org.eclipse.osgi and org.eclipse.core.runtime
directly. We need to start the platform by calling EclipseStarter. The
EclipseStarter will use another classloader to load the Eclipse Platform.
  
So, I think our solution could be as follow: 
1. In the java application, use EclipseStarter to start Eclipse Platform.
2. Configure the Eclipse Platform so that workbench and other UI related
plug-ins won't be loaded. (Actually, only org.eclipse.osgi and org.eclipse.core.runtime
are needed). 
3. If the Java application needs to use the Eclipse core functionality
(e.g. Platform.getBundle(symbolicName), platform.getExtensionRegistry(),
etc.), we need to use the classloader's functions to find the class instance
and then call the function in the class instance. 
  
Is this solution feasible? Did anyone do it before? I think the extension
framework is a very nice feature of Eclipse. If we can use it in server
applications, it will make Eclipse core even greater! Since I'm new to
Eclipse Platform Core, this idea might be unrealistic. But anyway, I just
want to start the discussion, because I think the goal is great, it will
make Eclipse Platform more popular and benefit other developers. Your thoughts
and comments are highly welcome! 
  
Thanks, 
Kai 
  
  
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