[
http://jira.qos.ch/browse/LBCLASSIC-184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=11512#action_11512
]
Hugues Malphettes commented on LBCLASSIC-184:
---------------------------------------------
Hi Ceki and Gunnar,
I had the privilege to receive an email by Gunnar about this.
So if that helps I can provide some background.
Gunnar is working on adding slf4j and logback to eclipse orbit's bundles.
In Orbit, the common procedure is to repackage things. It is in fact mandated
by eclipse as they will sign the bundles they distribute.
There are small changes (that I would be happy to file as request for
improvement to slf4j and logback if you want): name the bundles by the main
base package they export: Bundle-SymbolicName: slf4j-api will read
org.slf4j.api and others.
Gunnar needs to use resolve the cyclic dependency reported
http://bugzilla.slf4j.org/show_bug.cgi?id=75 and the simplest and most proven
approach really is to use fragments.
So now OSGi when it resolves a class actually resolves a package. Then goes in
the package to find the class and will fail if the class is not there.
It will also identify cyclic dependencies between packages.
Here is the situation (copied and pasted from Gunnar's email with some extra
comments):
<quote>
#1- org.slf4j.api bundle (as discussed: slf4j-api.jar)
#2- ch.qos.logback.core + classic bundles (<extra-comment>bundle with
logback-core and logback-classic except for the org.slf4j.impl</extra-comment>)
Imports: org.slf4j, org.slf4j.spi, org.slf4j.helpers
#3- ch.qos.logback.slf4j bundle (fragment delivers native SLF4J logger:
<extra-comment>if I understood correctly this contains the org.slf4j.impl of
logback-classic</extra-comment>)
Host: org.slf4j.api
Exports: org.slf4j.impl
Imports: ch.qos.logback.*
</quote>
So now we have a cycle because #3 contains org.slf4j.impl.LogbackMDCAdapter
which depends on #2.
Gunnar broke it by moving org.slf4j.impl.LogbackMDCAdapter into a different
package to that he can keep it with logback-classic (bundle #2)
I am guessing the main motivation behind #3 is to respect the conventions in
orbit related to having different packages for each base package they export.
I think this is a good enhancement to logback as it is nice to be able to have
more choices for its packaging and in general a good idea to really keep
objects in separate packages when they are related to different implementations
that will be potentially be packaged separately.
I am not very comfortable with #3 if you ask me but that is probably not the
main topic of this bug.
I hope this helps.
Hugues
> Remove Cyclic Dependencies between Classic, SLF4J API and SLF4J Impl
> --------------------------------------------------------------------
>
> Key: LBCLASSIC-184
> URL: http://jira.qos.ch/browse/LBCLASSIC-184
> Project: logback-classic
> Issue Type: Task
> Components: Other
> Affects Versions: 0.9.18
> Reporter: Gunnar Wagenknecht
> Assignee: Logback dev list
> Attachments: context-selector.patch, mdc-move.patch
>
>
> When working with Logback as OSGi bundles I found some issues regarding
> cyclic dependencies. Basically, code in "org.slf4j.impl" depends on
> "org.slf4j.api" as well as Logback classic. This is fine. However, code in
> Logback classic also depends on "org.slf4j.impl". This introduces a cycle.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://jira.qos.ch/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
_______________________________________________
logback-dev mailing list
[email protected]
http://qos.ch/mailman/listinfo/logback-dev
