[slf4j-dev] OSGi support in slf4j

[Hugues Malphettes]

Hi Ceki,
Thanks for reminding us to review the changes introduced by BND.

On Mon, Nov 1, 2010 at 2:16 PM, Ceki Gülcü <ceki at qos.ch> wrote:

> Hello all,
>
> I pulled in changes made by Heiko http://github.com/ceki/slf4j/pull/2.
> Here is the version of the MANIFEST file from slf4j-api-1.6.1.jar.
>
> Manifest-Version: 1.0
> Archiver-Version: Plexus Archiver
> Created-By: Apache Maven
> Built-By: ceki
> Build-Jdk: 1.6.0_16
>
> Bundle-Description: The slf4j API
> Bundle-Version: 1.6.1
> Implementation-Version: 1.6.1
> Implementation-Title: slf4j-api
> Bundle-ManifestVersion: 2
> Bundle-SymbolicName: slf4j.api
> Bundle-Name: slf4j-api
> Bundle-Vendor: SLF4J.ORG
> Bundle-RequiredExecutionEnvironment: J2SE-1.3
> Export-Package: org.slf4j;version=1.6.1, org.slf4j.spi;version=1.6.1,
>  org.slf4j.helpers;version=1.6.1
> Import-Package: org.slf4j.impl;version=1.6.0
>
> Here is the version generated after Heiko's changes have been applied:
>
> Manifest-Version: 1.0
>
> Export-Package: org.slf4j.spi;uses:="org.slf4j";version="1.6.2.SNAPSHO
>  T",org.slf4j.helpers;uses:="org.slf4j.spi,org.slf4j";version="1.6.2.S
>  NAPSHOT",org.slf4j;uses:="org.slf4j.helpers,org.slf4j.spi";version="1
>  .6.2.SNAPSHOT"
> Ignore-Package: org.slf4j.impl
> Implementation-Title: slf4j-api
> Built-By: ceki
>
> Tool: Bnd-0.0.357
> Bundle-Name: SLF4J API Module
> Created-By: Apache Maven Bundle Plugin
> Bundle-RequiredExecutionEnvironment: J2SE-1.4
> Bundle-Vendor: QOS.ch
> Build-Jdk: 1.6.0_16
>
> Bundle-Version: 1.6.2.SNAPSHOT
> Bnd-LastModified: 1288644768461
> Bundle-ManifestVersion: 2
>
> Bundle-License: http://www.opensource.org/licenses/mit-license.php
> Bundle-Description: The slf4j API
> Bundle-DocURL: http://www.qos.ch
> Bundle-SymbolicName: org.slf4j.api
>
> Import-Package: org.slf4j;version="[1.6.2.SNAPSHOT,1.7)",org.slf4j.hel
>  pers;version="[1.6.2.SNAPSHOT,1.7)",org.slf4j.spi;version="[1.6.2.SNA
>  PSHOT,1.7)"
>
> Admittedly, I am a little lost. The previous MANIFEST file imported
> org.slf4j.impl, whereas the latest MANIFEST does not. Strangely enough,
> org.slf4j.impl is not mentioned at all.


Heiko packages org.slf4j.impl as bundle fragments that are hosted by
org.slf4j.api.
In our situation, there must not be more than one provider of
org.slf4j.impl: this means there must one and exactly one fragment that
provides org.slf4j.impl.
At runtime the fragment classes are part of the classloader of
org.slf4j.api.
This is why org.slf4j.api does not import org.slf4j.impl at all.

The MANIFEST.MF of org.slf4j.api does look good.
It contains a few of extra lines that are read by BND alone: Private-Package
and Bnd-LastModified for example.

The MANIFEST.MF of jcl.over.slf4j (aka jcl-over-slf4j) uses these
statements:
Export-Package: org.apache.commons.logging;version=1.1.1,  org.apache.
 commons.logging.impl;version=1.1.1
Import-Package: org.slf4j;version=1.6.2.SNAPSHOT, org.slf4j.spi;versio
 n=1.6.2.SNAPSHOT

It will work.
The versioning constrain on the import-package is I think too much: strictly
speaking, the produced fragment is going to work with version 1.6 of slf4j.
I apologize for sounding picky and in the case where we always build and
distribute together slf4j-api and jcl-over-slf4j it probably does not matter
much.
If we were to adopt BND to generate the MANIFESTs of logback let's make sure
that we generate version=1.6 only so that we don't suddenly force everyone
to upgrade both slf4j and logback at once for no actual reason.

Best regards,
Hugues


>
> In earlier message Heiko wrote:
>
> > As all the logging backends are fragments I excluded org.slf4j.impl
> > package from imported packages. This means you can install the
> > slf4j-api bundle in an OSGi container successfully without a backend. >
> Not sure whether this is what we want.
>
> I think it makes life easier if the slf4j-api bundle can be installed
> without a back-end. However, this is assuming that a desired back-end bundle
> can be installed and successfully bound with slf4j-api. (It is an obvious
> requirement but still may be useful to mention.)
>
> This version can be pulled in either from
> http://github.com/weiglewilczek/slf4j (master) or from
> http://github.com/ceki/slf4j (weiglewilczek-master).
>
> Your comments are most welcome,
>
> --
> Ceki
>
> _______________________________________________
> slf4j-dev mailing list
> slf4j-dev at qos.ch
> http://qos.ch/mailman/listinfo/slf4j-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://qos.ch/pipermail/slf4j-dev/attachments/20101102/938ad3ec/attachment-0001.html>