Bruce has shown us a great article that clearly explains the issues and
solutions:
http://www.qos.ch/logging/classloader.jsp
It describes this problem in detail...and it says (near the bottom) for
a solution:
"For Tomcat 5.0.27 and later,
<snip>
4. Do not include any other copies of commons-logging.jar and
log4j.jar in your web-applications' WEB-INF/lib/ directory.
<snip>
"
So...do we really want to hack up the classloader? Please read the
article..its fascinating. Thanks for the link, Bruce.
Jeff
Bruce Snyder wrote:
On 9/27/05, Kevan Miller <[EMAIL PROTECTED]> wrote:
Good point. I didn't notice that they were including Commons in their
WEB-INF/lib. I think this is related to the context-priority-classloader
discussion I brought up last week.
Section 9.7.2 of the Servlet spec specifies that for a J2EE product "The
container should not allow applications to override or access the
container's implementation classes". Depending on your definition of
"implementation classes", Geronimo's servlet classloaders permit a number of
"implementation classes" (including commons-logging) to be loaded from the
web app's context. As this situation points out, this can lead to a number
of problems.
The same section of the same spec also states the following:
'It is recommended also that the application class loader be
implemented so that classes and resources packaged within the WAR are
loaded in preference to classes and resources residing in
container-wide library JARs.'
Tomcat is a good exmaple of this in that it provides each webapp its
own class loader. And therein lies the reason I have always
recommended that each webapp should handle it's own logging (i.e.,
contain it's own logging jars and configuration files) *completely
separate* from the app server. I've seen far too many webapps that
utilize the app server's logging mechanism for an individual webapp.
IMO, this is simply wrong becuase it's using what I consider to be a
side effect as a feature.
Bruce
--
perl -e 'print unpack("u30","D0G)[EMAIL
PROTECTED]&5R\"F)R=6-E+G-N>61E<D\!G;6%I;\"YC;VT*"
);'
The Castor Project
http://www.castor.org/
Apache Geronimo
http://geronimo.apache.org/
