Author: skitching
Date: Wed Apr 19 03:39:49 2006
New Revision: 395202
URL: http://svn.apache.org/viewcvs?rev=395202&view=rev
Log:
Add information about some containers effectively forcing parentFirst=true for
JCL classes.
Modified:
jakarta/commons/proper/logging/trunk/RELEASE-NOTES.txt
jakarta/commons/proper/logging/trunk/xdocs/guide.xml
jakarta/commons/proper/logging/trunk/xdocs/troubleshooting.xml
Modified: jakarta/commons/proper/logging/trunk/RELEASE-NOTES.txt
URL:
http://svn.apache.org/viewcvs/jakarta/commons/proper/logging/trunk/RELEASE-NOTES.txt?rev=395202&r1=395201&r2=395202&view=diff
==============================================================================
--- jakarta/commons/proper/logging/trunk/RELEASE-NOTES.txt (original)
+++ jakarta/commons/proper/logging/trunk/RELEASE-NOTES.txt Wed Apr 19 03:39:49
2006
@@ -51,6 +51,12 @@
Jakarta Commons Logging wiki site:
http://wiki.apache.org/jakarta-commons/Logging
+Note that some containers (some versions of Apache Tomcat and JBoss in
+particular) prevent webapps, ejbs, etc from overriding the commons-logging
+implementation provided by the container. This means that bundling this
+updated implementation with a deployed application may not have any effect.
+See the commons-logging site and/or the wiki for more information.
+
== New Features ==
* Jar files now have release-numbers embedded in the names, for easier
management.
Modified: jakarta/commons/proper/logging/trunk/xdocs/guide.xml
URL:
http://svn.apache.org/viewcvs/jakarta/commons/proper/logging/trunk/xdocs/guide.xml?rev=395202&r1=395201&r2=395202&view=diff
==============================================================================
--- jakarta/commons/proper/logging/trunk/xdocs/guide.xml (original)
+++ jakarta/commons/proper/logging/trunk/xdocs/guide.xml Wed Apr 19 03:39:49
2006
@@ -113,7 +113,9 @@
In most cases, including the (full) <code>commons-logging.jar</code> in the
classpath
should result in JCL configuring itself in a reasonable manner.
There's a good chance that it'll guess your preferred logging system and you
won't
-need to do any configuration at all!
+need to do any configuration at all! Note, however, that providing a simple
+commons-logging.properties file which specifies the concrete logging library
to be
+used is recommended, as it saves any possible confusion.
</p>
<subsection name='Configuration'>
<p>
Modified: jakarta/commons/proper/logging/trunk/xdocs/troubleshooting.xml
URL:
http://svn.apache.org/viewcvs/jakarta/commons/proper/logging/trunk/xdocs/troubleshooting.xml?rev=395202&r1=395201&r2=395202&view=diff
==============================================================================
--- jakarta/commons/proper/logging/trunk/xdocs/troubleshooting.xml (original)
+++ jakarta/commons/proper/logging/trunk/xdocs/troubleshooting.xml Wed Apr 19
03:39:49 2006
@@ -328,5 +328,73 @@
</subsection>
</subsection>
</section>
+ <section name='Containers With Custom ClassLoading Behaviour for Logging'>
+ <p>
+ Because commons-logging is such a fundamental library, some containers modify
the way
+ in which classloading behaves for commons-logging classes.
+ </p>
+ <subsection name="Apache Tomcat">
+ <p>
+ At the current date, Tomcat 5.5.16 is the current release. All releases from
version
+ 4.1.x through 5.5.16 have a startup process that places jarfile
+ ${tomcat.home}/bin/commons-logging-api.jar in the system classpath and then
+ prevents any webapp from overriding the classes in that jarfile. Effectively,
all
+ webapps behave as if "parent-first" classloading were enabled for those
classes.
+ </p>
+ <p>
+ This has some benefits; in particular it means that there are no problems in
+ these Tomcat versions with having multiple copies of the commons-logging Log
+ interface in the classpath (which avoids the "Log does not implement Log"
+ problem described elsewhere).
+ </p>
+ <p>
+ However it also means that no webapp can override the core commons-logging
+ classes by including an updated commons-logging jarfile in WEB-INF/lib; any
+ class already loaded via the container takes priority. In particular, as
+ Tomcat bundles logging 1.0.4 only, the new diagnostics and
memory-leak-prevention
+ features of the 1.1 release will not be available unless the container's
+ library version is updated.
+ </p>
+ <p>
+ Because the commons-logging-api.jar in the container does not contain any
+ log-library-adapter classes, updated behaviour for these <i>will</i> be
+ seen when logging 1.1 is bundled in WEB-INF/lib. In particular, the
+ support for log4j's TRACE level will take effect without having to update
+ the container.
+ </p>
+ <p>
+ If you do wish to update Tomcat's version of commons-logging, then you
+ <i>must</i> use the commons-logging-1.1-api jar only, not the full jar.
+ Classes in the webapp cannot override classes loaded from the system
+ classpath set up during Tomcat's startup process, and logging adapters
+ can only see their matching concrete logging library if that library is
+ available in the same classpath. Bundling the full commons-logging jarfile
+ (with adapters) into the system classpath therefore means that logging
+ libraries (eg log4j) within WEB-INF/lib are not accessable.
+ </p>
+ <p>
+ Note that the behaviour described here only applies if the standard Tomcat
+ startup process is run. When Tomcat is embedded in a larger
+ framework (eg run embedded within an IDE) this may not apply.
+ </p>
+ </subsection>
+ <subsection name="JBoss Application Server">
+ <p>
+ The JBoss Application Server can be configured to prevent deployed
+ code from overriding classes higher in the hierarchy, effectively
+ forcing "parent-first" behaviour for selected classes. By default,
+ commons-logging is in this list (at least for some JBoss versions
+ starting with 4.0.2), and therefore including an updated version
+ of commons-logging in WEB-INF/lib or similar will have no effect.
+ See the JBoss classloading documentation for more details.
+ </p>
+ </subsection>
+ <subsection name="Other Containers">
+ <p>
+ As more information becomes available on this topic, it may be added
+ to the commons-logging wiki site.
+ </p>
+ </subsection>
+ </section>
</body>
</document>
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