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From "Simon Kitching (JIRA)" <>
Subject [jira] Commented: (LOGGING-114) Silent Swallowing of NoClassDefFoundError
Date Wed, 11 Jul 2007 20:22:04 GMT


Simon Kitching commented on LOGGING-114:

JCL has adopted the principle that logging problems should never stop an app from running.
In the past exceptions from logging libs were allowed through JCL in some cases and there
were loud user complaints. In many cases, the users didn't actually *want* logging output
anyway, and didn't know how to fix the logging problems because they were complex and involved
classloaders with different classpaths etc. So now, JCL *never* fails to init. In particular,
if log4j is present but cannot be initialised (eg due to classloader problems) JCL quite deliberately
ignores this problem and lets the app start.

If someone really does want logging output but aren't getting what they expect *then* they
can turn on JCL diagnostic output to see what's happening. 

I don't think there is likely to be agreement for any change to JCL's behaviour for this.

Writing problems stuff to stdout etc is also unacceptable when diagnostics are not enabled.
Again, this can cause problems for users who don't actually care about logging output anyway.

However I would agree that when diagnostics are enabled, JCL should write out the message
from the original exception. If it's not doing this then I would call that a bug.

> Silent Swallowing of NoClassDefFoundError
> -----------------------------------------
>                 Key: LOGGING-114
>                 URL:
>             Project: Commons Logging
>          Issue Type: Bug
>    Affects Versions: 1.1.0
>         Environment: Various OSs, in combination with log4j 1.2.14.
>            Reporter: Malcolm Cleaton
>            Priority: Minor
> Hi. I'm using commons logging with log4j; my team ship a library which uses log4j, and
some of our clients use it with commons-logging.
> If commons-logging is in its default configuration, and log4j is present but fails to
load its configuration with an unhandled exception, the results are pretty nasty:
> - commons-logging silently swallows the exception and logs with something else. If diagnostics
are turned on, the message is:
>     Could not instantiate Log 'org.apache.commons.logging.impl.Log4JLogger' -- java.lang.reflect.InvocationTargetException:
> - future attempts to use log4j directly get a pretty unhelpful error:
>     java.lang.NoClassDefFoundError at org.apache.log4j.Logger.getLogger(
> I realise you're trying to deal with a very large number of cases in this code, but it
does seem like something better could be done here. If nothing else is possible, at least
recognising the InvocationTargetException and pulling out the target exception for the diagnostic
log would have helped with tracking this one down.

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