Re: Re[2]: [platform-core-dev] Can I use Eclipse Platform Core functiona

[Thomas Watson <tjwatson@xxxxxxxxxx>]

Peter,

If someone else (besides the Framework)
sets themselves as the URLStreamHandlerFactory then the Framework will
have problems trying to run.  

-  First of all, it will prevent
the framework from defining the protocols used to access bundle resource/entry
URLs.  There may be other ways of doing this but the current implementation
in eclipse uses the URLStreamHandlerFactory registered by the framework
to locate the proper URLStreamHandler to use for the bundle resource/entry
URLs.  This will not become evident until someone uses a bundle resource/entry
URL as a context to create a new URL or if someone constructs a new URL
using the output of toExternalForm() from a bundle resource/entry URL.
 For example,

Bundle b;
URL entry = b.getEntry("somefile.txt");
URL url1 = new URL(entry, "someotherfile.txt");
URL url2 = new URL(entry.toExternalForm());

This may seem like a strange usecase
but keep in mind that bundle resource/entry URLs are used by the classloaders
in OSGi.  We do not have control over what 3rd party code is doing
with the URLs returned by ClassLoader#getResource.  As a result we
have to support construction of URLs using one of our bundle resource/entry
URLs as a context.  Otherwise many 3rd party software will start to
fail with unsupported protocol exceptions.

-  If the framework cannot set
the URLStreamHandlerFactory (and the ContentHandlerFactory) for the VM
then the framework cannot support the URL Handler Service Specification
in OSGi.  The eclipse runtime uses this specification to register
additional protocols which are used by the rest of eclipse.  If this
functionality is not available then eclipse will not function.

I know of other projects that are having
to deal with this.  In Eclipse 3.0 we had to deal with this because
Eclipse 2.x used to register its own URLStreamHandlerFactory with the VM
to support the additional protocols (i.e platform: protocol).  Now
eclipse 3.0 uses the URL Handler Service Specification to add additional
protocol support.  There are other projects that are investigating
using the URL Handler Service Specification to plugin their own additional
protocols instead of setting the URLStreamHandlerFactory themselves.

Tom.

platform-core-dev-bounces@xxxxxxxxxxx wrote on 04/13/2005
04:35:39 AM:

> This should be easy to prevent by setting it yourself before you start
> the framework.
> 
> However, I am a bit confused. The framework should preserve the
> existing handlers and it allows new handlers to be added. So what
is
> the problem?
> 
> Kind regards,
> 
>      Peter Kriens
>