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Re: [orbit-dev] Slf4j into Orbit

Oberhuber, Martin wrote:
Hi Thomas,

Getting your slf4j bundle into Orbit seems like a great idea,
especially taking into account that you have already mastered
a roadblock that everyone was likely to run into!

I'm wondering what kinds of org.slf4j.impl implementations you have already finished for Buckminster?

We have an implementation that redirects to the Buckminster logger that in turn uses the Eclipse logger. It consists of two classes. A factor with one method that returns an instance of the logger implementation (a one liner) and the implementation that dispatches the logger methods (about 30 methods with one line in each).

You can view both source projects in our SVN repository:

Also, I'm not sure I understand what you say about the extension
point. given that slf4j is quite low-level, doesn't that introduce an unwanted dependency on the Eclipse plugin
registry? Would it make sense to consider using an OSGi
Service instead? [haven't done that myself so far, though].
That would be another way to do it. I chose to use an extension since I felt that given some other OSGi framework you can probably use the SLF4J as it stands today and disregard the circular dependencies. It's only a problem when you use PDE.

My other thought is, is the circular dependency really a problem
for a user of the pre-built binary slf4j? I'd think that when
I have a circular dependency, and one part of the circle is
already built, fixed and unchangeable, the circle should break
by itself since it always ends at the pre-built item?

It becomes a problem for sure as soon as you want to create your own implementation. Using the existing binary implementations for say, log4j will work I guess. I haven't tried it though.

- thomas

Martin Oberhuber, Senior Member of Technical Staff, Wind River
Target Management Project Lead, DSDP PMC Member
-----Original Message-----
From: orbit-dev-bounces@xxxxxxxxxxx [mailto:orbit-dev-bounces@xxxxxxxxxxx] On Behalf Of Thomas Hallgren
Sent: Saturday, January 26, 2008 11:23 AM
To: Orbit Developer discussion
Subject: Re: [orbit-dev] Slf4j into Orbit

I've been using SLF4J for Buckminster. We encountered a problem with it in that it introduces a circular dependency on package level.

SLF4J exports an API package and imports an SPI. An implementor must import the API and export the SPI. The circular dependency is a fact and this cannot be used in Eclipse

In order to work around this, I created a new bundle called org.slf4j.extendable. It exports the API but it implements the SPI by itself. The implementation is an abstraction that expects an implementor to extend the extension point 'org.slf4j.impl' It bundles only the API part of the SLF4J and only as a binary so no alterations were made on existing code.

I'd be happy to submit this to Orbit (doing so was in the back of my mind when I created this bundle).

Thomas Hallgren

t assumes that another package implements (and imports) an spi package that it then exports. It imports
Simon Kaegi wrote:
SLF4J is quite an interesting library in that it provides a
relatively OSGi
friendly logging facade. I've already gone through the
initial CQ round
here when I was experimenting with an updated OSGi logging story.
I didn't move this into Orbit simple because I haven't had
time to really
make use of it. The approved version was from about a year
ago so there
maybe value in doing an update.

As an aside you mention Jetty 6 -- we just got approval for
Jetty 6.1.7 and
Servlet 2.5.
We also have signoff to update the exisiting Jetty  to 5.1.14.
These will be coming soon to Orbit.

I believe Jetty 6.1.7 has dropped the SLF4J dependency so
barring any
unforseen problems I'm not planning on adding SLF4J to
Orbit for now.
Feel free to go ahead yourself.


orbit-dev-bounces@xxxxxxxxxxx wrote on 01/24/2008 10:21:52 AM:

It doesn't hurt to try if you need it, so +1


Chris Aniszczyk | IBM Lotus | Eclipse Committer | http://mea-bloga. | +1.860.839.2465


"Oberhuber, Martin" <Martin.Oberhuber@xxxxxxxxxxxxx>


"Orbit Developer discussion" <orbit-dev@xxxxxxxxxxx>


01/24/2008 07:22 AM


[orbit-dev] Slf4j into Orbit

Hi all,

has anybody considered getting Slf4j into Orbit yet?

It looks like Slf4j ("Simple Logging Facade for Java") is
a prerequisite
for lots of other libraries, including Jackrabbit which
I'm considering
for WebDAV support, and Jetty6 which the Platform or
Equinox might be
interested in at some point.

They have a specific license which they claim to be
identical to the MIT
license and deemed to be compatible with virtually all types of

So there might be a good chance to get it approved for Eclipse.

I don't think I need this immediately, but given that the Ganymede
Cutoff date is Jan.31 I was wondering whether it might be
a good idea to
get this on the plate. What do you folks think?

Martin Oberhuber, Senior Member of Technical Staff, Wind River
Target Management Project Lead, DSDP PMC Member
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