[slf4j-dev] [Bug 75] New: Cyclic dependency in OSGi

[bugzilla-daemon at pixie.qos.ch]

http://bugzilla.slf4j.org/show_bug.cgi?id=75

           Summary: Cyclic dependency in OSGi
           Product: SLF4J
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Core API
        AssignedTo: dev at slf4j.org
        ReportedBy: mirkojahn at gmail.com


The API bundle of SLF4j (slf4j-api-1.X.0.jar) exports the API packages and
imports the org.slf4j.impl package. All implementation bundles like LOGBack in
return have to import the API packages and export their impl. of
org.slf4j.impl.* classes. This creates a pretty nasty cycle, although it might
not be necessary to have a concrete implementation available, if logging is not
desired in a particular deployment for instance. For this reason, the import
should be defined as optional:
Import-Package: org.slf4j.impl;version=${project.version};resolution:=optional

OSGi would then look internally (inside the API bundle) for the resources/
classes, where a default Logger could be returned, which is doing nothing. 

BTW, the export statements are missing the uses clause and all exports should
be imported as well (see blog entries of Peter Kriens). Here is an example
(generated with Eclipse Manifest-Editor):

Export-Package: org.slf4j;version="1.4.3";uses:="org.slf4j.spi",
 org.slf4j.helpers;version="1.4.3";uses:="org.slf4j.spi,org.slf4j",
 org.slf4j.spi;version="1.4.3";uses:="org.slf4j"
Import-Package: org.slf4j;version="[1.4.0,2.0.0)",
 org.slf4j.helpers;version="[1.4.0,2.0.0)",
 org.slf4j.spi;version="[1.4.0,2.0.0)",
 org.slf4j.impl;version="[1.4.0,2.0.0)";resolution:=optional


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