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Date: Fri, 24 Feb 2006 17:44:42 +0100
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From: Ceki =?iso-8859-1?Q?G=FClc=FC?= <listid@qos.ch>
Subject: RE: [ApacheDS] JBoss compatibility?
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At 04:49 PM 2/24/2006, Endi S. Dewata wrote:
>Hi Ceki,
>
> > Which version of NLOG4J and ApacheDS are you using? Versions of NLOG4J
> > prior to 1.2.16 did indeed have a runtime compatibility issue with=
 log4j.
> > However, NLOG4J version 1.2.16 and later should not suffer from the
> > problem you describe. Thus, it is important to know the version of
> > ApacheDS and NLOG4j that you are using.
>
>I'm checking out the latest ApacheDS (version 1.0 RC1) from the svn trunk,
>the apacheds/core/pom.xml says that it's using nlog4j version 1.2.19.
>
>I also downloaded JBoss 4.0.3 SP1 source code, and there is a log4j.jar=
 file
>in thirdparty/apache-log4j/lib directory which should be version 1.2.8
>according to component-info.xml.
>
>So I tried compiling a small program using Log4j API:
>
>   import org.apache.log4j.*;
>
>   public class Test {
>       public static void main(String args[]) {
>           Logger log =3D Logger.getLogger(Test.class);
>           log.debug("Test");
>       }
>   }
>
>I compiled it with nlog4j-1.2.19.jar, then I tried to run it with log4j.jar
>from JBoss, then I got this error:
>
>Exception in thread "main" java.lang.NoSuchMethodError:
>org.apache.log4j.Logger.debug(Ljava/lang/Str
>ing;)V
>
>It looks like the nlog4j has a debug(String) but the log4j doesn't.
>
>I also tried the following program using SLF4J API:
>
>   import org.slf4j.*;
>
>   public class Test {
>       public static void main(String args[]) {
>           Logger log =3D LoggerFactory.getLogger(Test.class);
>           log.debug("Test");
>       }
>   }
>
>I compiled it with nlog4j-1.2.19.jar, then I tried running it with=
 log4j.jar
>and nlog4j-1.2.19.jar in the class path in this order, then I got this
>error:
>
>   Exception in thread "main" java.lang.IncompatibleClassChangeError
>
>The error also occurs when executing log.debug(...) statement.
>
>If I reverse the order of the jar files, it will work fine because nlog4j
>will be loaded first. However in JBoss this is not possible because JBoss
>classes will be loaded first before the SAR files. Any suggestions? Thank
>you very much.

Endi,

I think your description of the problem is quite valuable.

Compilation against NLOG4J is sticky, in the sense that you cannot later=20
revert back to log4j. However, I think that this is not the problem you are=
=20
facing. As far as I know ApacheDS does not invoke log4j directly, it=20
invokes the SLF4J API instead. From what you describe, the mere presence of=
=20
log4j in JBoss' class loader path, messes up SLF4J's NLOG4J binding.

As an immediate fix, you can just replace JBoss' copy of log4j with NLOG4J.=
=20
This should fix the problem as far as you are concerned. Another perhaps=20
better solution, is to replace nlog4j.jar which ships with ApacheDS with=20
slf4j-log4j12.jar without replacing any jar files in JBoss. FYI,=20
slf4j-log4j12.jar ships with the SLF4J distribution.

I guess that this should be added to ApacheDS documentation in order to=20
avoid similar inconveniences to other JBoss+ApacheDS users. Maybe that is=20
already the case?

>--
>Endi S. Dewata

--=20
Ceki G=FClc=FC