JULI-dedicated jcl-over-slf4j library

This project is a solution for using SLF4J and Logback as Tomcat internal logging system.

This library is a re-packaged bundle of jcl-over-slf4j, SLF4J and Logback, highly inspirated by tomcat-slf4j-logback. This was done in the context of documenting the juli-to-slf4j bridge and its alternatives.

It builds an additional library that plugs into the tomcat-extras-juli “extra” component to provide SLF4J logging with the Logback backend, keeping the tomcat-extras-juli library separate, and unmodified. (Contrarily to tomcat-slf4j-logback, which retains only a portion of the default tomcat-juli in order to build a smaller library.)

This lib provides:

1. A JULI-dedicated bridge from the full JCL implementation of tomcat-extras-juli and a package-renamed SLF4J API.

2. Package-renamed SLF4J & Logback libraries, so that they might not conflict with any SLF4J & Logback that web applications may ship with.

Web applications that ship with their own SLF4J & Logback libraries will properly create separate logging contexts. This is the simple approach. The configuration in conf/logback-catalina.xml shall use the package-renamed code, prepending com.apache.juli. to all Logback class names. JNDI cannot be setup since Logback intializes before the Tomcat JNDI system is ready.

Caveats

The tomcat-extras-juli-over-slf4j.jar must appear before the tomcat-extras-juli.jar on the $CLASSPATH as detailed below. Indeed, the default org.apache.juli.logging.LogFactory is not suppressed from the original tomcat-extras-juli.jar. It is just masked by the one provided by tomcat-extras-juli-over-slf4j.jar. Any reason for a non-guraanteed classpath order would result in a non-working system.

Running Tomcat with a security manager requires some more setup in conf/catalina.policy.

Setup

1. Build the lib

mvn clean package

2. Copy the resulting target/tomcat-extras-juli-over-slf4j-1.7.12.jar to the $CATALINA_BASE/bin/ directory.

3. Add the Bash code below to your $CATALINA_BASE/bin/setenv.sh script.

# Logging configuration
# Because the juli config needs to be set early at bootstrap time

# Deactivate standard JULI config (the correct way by Bugzilla #45585)
LOGGING_CONFIG="-Dnop"

# Add bridge to the class path
CLASSPATH="${CLASSPATH:+$CLASSPATH:}$CATALINA_BASE"/bin/tomcat-extras-juli-over-slf4j-1.7.12.jar

# Activate diagnostics in LogFactory of 'tomcat-extras-juli'
# Actually non are output because the original JULI LogFactory is masked
# by the one provided by 'juli-jcl-over-slf4j' above
CATALINA_OPTS="$CATALINA_OPTS -Dorg.apache.juli.logging.diagnostics.dest=STDOUT"

# Setup config file
CATALINA_OPTS="$CATALINA_OPTS -Djuli.logback.configurationFile=$CATALINA_BASE/conf/logback-catalina.xml"

4. Remove the default $CATALINA_BASE/conf/logging.properties because it's no use keeping it anymore.

5. Restart Tomcat.

Author and Licenses

Copyright © 2015, Benjamin Gandon

The JULI-JCL-over-SLF4J library is released under the terms of the Apache 2.0 license, excepted some specific sub-components, as detailed in LICENSES.md.