Tomcat + SLF4J + Logback

Tomcat SLF4J Logback is a drop in replacement to tomcat allowing full all internal logging to use our favorite slf4j/logback libraries.

RELEASES

Quick Start

If you quickly want to configure Tomcat to use Slf4J and Logback, just download latest package available from github releases into $CATALINA_HOME. Be advised doing so will replace server.xml with default version and logging valve!

The following directions are for manual setup.

After downloading copy as follows:

bin/tomcat-juli.jar to $CATALINA_HOME/bin (replacing existing tomcat-juli.jar)
bin/setenv.sh or bin\setenv.bat to $CATALINA_HOME/bin (this script contains proper variable name and doesn't require any changes, unless you have your own version of setenv.sh/setenv.bat script)
conf/logback.xml to $CATALINA_HOME/conf
conf/logback-access.xml to $CATALINA_HOME/conf (older version was called logback-access-localhost.xml)
conf/server.xml to $CATALINA_HOME/conf (this file contains proper valve and doesn't require any changes, unless you have your own version of server.xml)
lib/logback-core-1.3.11.jar to $CATALINA_HOME/lib
lib/logback-access-1.3.11.jar to $CATALINA_HOME/lib

Delete $CATALINA_HOME/conf/logging.properties. This will turn off java.util.logging completely.

If you use your own setenv.sh in $CATALINA_BASE/bin, the default one $CATALINA_HOME/bin/setenv.sh will not be used, so you have to define juli-logback.configurationFile Java property in your local setenv.sh manually. You can define it to use default configuration file like in bin/setenv.sh or to use any other located on your filesystem, just make sure that Tomcat process will have enough privileges to read it.

conf/logback.xml tries to reflect original Tomcat logging configuration. Feel free to change it.

When using your own preconfigured server.xml, the following will need applied.

Add (if using legacy logback-access-localhost.xml):

<Valve className="ch.qos.logback.access.tomcat.LogbackValve" quiet="true"
   filename="conf/logback-access-localhost.xml" />

Add (if using logback defined naming logback-access.xml which allows it to auto discover)

<Valve className="ch.qos.logback.access.tomcat.LogbackValve" quiet="true" />

to $CATALINA_HOME/conf/server.xml.

Remove:

<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
    prefix="localhost_access_log." suffix=".txt"
    pattern="%h %l %u %t &quot;%r&quot; %s %b" />

from $CATALINA_HOME/conf/server.xml.

Final step: run $CATALINA_HOME/bin/startup.sh (or startup.bat). Voila!

Maven Central Distribution

Maven central distribution is available. Zip binaries contain same as github releases. Below are tomcat-juli jars.

For users to get release, use dependency as follows.

<dependency>
    <groupId>com.github.tomcat-slf4j-logback</groupId>
    <artifactId>tomcat10-slf4j-logback</artifactId>
	<version>${tomcat.version}</version>
</dependency>

The tomcat-slfj4-logback binary must be renamed as tomcat-juli to use within a tomcat build.

Site Page

Site page is located here

Details

This project allows using SLF4J and Logback in Apache Tomcat absolutely without the need for commons- logging, log4j, and java.util.logging.

This project's main and only goal is to allow the following:

redirect all org.apache.commons.logging (repackaged to org.apache.juli.logging) calls to org.slf4j (repackaged to org.apache.juli.logging.org.slf4j) - i.e. handle internal tomcat logging with slf4j and logback binding,
make still possible to use logback-access with logback-access.xml config - using standard functionality of logback-access,
make possible to use independent configuration of slf4j+logback from all web applications which may carry their own slf4j-api, logback-core, and logback-classic in their WEB-INF/lib directory.
make possible to use logstash-logback-encoder for logging in JSON format.

Using only Mavens pom.xml file, proper source JARs are downloaded from maven repository and unpacked. Then all classes are refactored under org.apache.juli.logging package/subpackages and then compiled.

To allow web applications to use their own slf4j-api and logback-classic, classes used by Tomcat (particularly jcl-over-slf4j) must go into different, non-standard packages. According to Tomcat Documentation web application looks up classes in their WEB-INF/classes directory and WEB-INF/lib/*.jar files before looking them in $CATALINA_HOME/lib, but after looking them in system class loader. So Tomcat needs only to have tomcat-juli replaced with versions of jcl-over-slf4j, slf4j-api, logback-core, and logback-classic refactored into different packages.

Finally, in order to keep the classpath clean, I've chosen the method of selecting Logback's configuration file using juli-logback.configurationFile system property. It is renamed in source files during refactoring phase. Leaving standard logback.configurationFile property would cause selecting this file in all web applications despite of having dedicated, classpath-based logback.xml configuration files.

There are four JARs involved in the process transformed into org.apache.juli.logging exactly the same way as commons-logging is transformed in Tomcat's build process. It is eventually compiled into tomcat-juli.jar

tomcat-juli is mandatory, because it is directly referenced during Tomcat's startup process while constructing system class loader. This JAR is transformed and placed in $CATALINA_HOME/bin/tomcat-juli.jar file.:

jcl-over-slf4j - commons logging over SLF4J JAR.
slf4j-api - main SLF4J JAR.
logback-core - core Logback JAR.
logback-classic - actual SLF4J binding JAR.

Installation

Launching the build requires Maven install - everything will be downloaded upon build.

Type:

mvn clean install

Tomcat version for 10 build requires jdk 11.

And move tomcat-juli JAR for your tomcat version from target directory to $CATALINA_HOME/bin directory.

More detailed instruction:

edit file pom.xml to update tomcat/slf4j/logback dependencies
run mvn clean install to build jar, javadoc, and source
run mvn site to generate site page
move tomcat-juli.jar from target directory to $CATALINA_HOME/bin.

After changing versions (e.g. for Tomcat), run mvn clean install.

Running Tomcat now will use default (very verbose) configuration of Logback. To change Logback's configuration, run Tomcat with the following system variable (using your favorite method of setting such variables - in catalina.sh, setenv.sh or other):

-Djuli-logback.configurationFile=file:<logback.xml location>

Alternative to allow git bash, remove the file: marker. It works using the bat or sh in this mode.

-Djuli-logback.configurationFile=<logback.xml location>

Configuration

Now you can configure whatever logging technology you want for your web applications. I recommend SLF4J and Logback because from now on, it will not collide with Tomcat's logging configuration.

While configuring Tomcat's logging, keep in mind that you have to use renamed packages in logback.xml config file, e.g.:

<configuration>
    <appender name="CONSOLE" class="org.apache.juli.logging.ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} %-5level {%thread} [%logger{20}] : %msg%n</pattern>
        </encoder>
    </appender>
    <root level="INFO">
        <appender-ref ref="CONSOLE" />
    </root>
</configuration>

Alternatively, you can use bundled Logstash encoder for logging in JSON format:

<configuration>
    <appender name="CONSOLE" class="org.apache.juli.logging.ch.qos.logback.core.ConsoleAppender">
        <encoder class="org.apache.juli.logging.net.logstash.logback.encoder.LogstashEncoder" />
    </appender>
    <root level="INFO">
        <appender-ref ref="CONSOLE" />
    </root>
</configuration>

Configuration of logback-access doesn't require renamed packages, as the required JARs are loaded from common class loader.

Sample logback.xml reflecting the configuration from standard $CATALINA_HOME/conf/logging.properties can be found in logback.xml.

Tomcat Customization

Tomcat 10.0.x

After unpacking apache-tomcat-10.0.x.zip, one can run Tomcat by executing $CATALINA_HOME/bin/startup.sh. This will cause running Tomcat with standard java.util.logging enabled. The standard command line is:

"java" \
    -Djava.util.logging.config.file="$CATALINA_HOME/conf/logging.properties"
    -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
    -Djava.endorsed.dirs="$CATALINA_HOME/endorsed"
    -classpath "$CATALINA_HOME\bin\bootstrap.jar"
    -Dcatalina.base="$CATALINA_HOME"
    -Dcatalina.home="$CATALINA_HOME"
    -Djava.io.tmpdir="$CATALINA_HOME"
    org.apache.catalina.startup.Bootstrap start

Deleting $CATALINA_HOME/conf/logging.properties will replace -Djava.util.logging.config.file with -Dnop.

Finally we must configure our tomcat-slf4j-logback integration:

place our tomcat-juli JAR in $CATALINA_HOME/bin
add -Djuli-logback.configurationFile=<logback.xml location> to $JAVA_OPTS in setenv.sh
if the above add does not work, add file: before <logback.xml location>

Now Tomcat's internal logging goes through org.apache.juli.logging.org.slf4j and org.apache.juli.logging.ch.qos.logback to appenders configured in $CATALINA_HOME/conf/logback.xml (or whatever file you set juli-logback.configurationFile variable to).

The final step is to configure logback-access. Now we don't have to deal with package manipulation. Just add:

Add (if using legacy logback-access-localhost.xml):

<Valve className="ch.qos.logback.access.tomcat.LogbackValve" quiet="true"
    filename="conf/logback-access-localhost.xml" />

Add (if using logback defined naming logback-access.xml which allows it to auto discover)

<Valve className="ch.qos.logback.access.tomcat.LogbackValve" quiet="true" />

to $CATALINA_HOME/conf/server.xml, place properly configured logback-access-localhost.xml on $CATALINA_HOME/conf and place logback-core and logback-access JARs into $CATALINA_HOME/lib. This won't cause problems with individual WARs' slf4j+logback configuration, because logback.xml is read by logback-classic which is recommended to reside in WEB-INF/lib. The only additional benefit is that WARs will see logback-core through common class loader.

Using Tomcat in Eclipse

Go to Window › Preferences › Server › Runtime Environments and add your server runtime as always
Go to Servers view and add server instance as always
Open server definition (RMB, Open or F3) and click open launch configuration
On Arguments tab in VM arguments add -Djuli-logback.configurationFile="<absolute tomcat home path>/conf/logback.xml"

That's all. While creating server runtime instance, eclipse generates VM arguments using absolute paths (no variables), so just copy the Tomcat home path and add -Djuli-logback.configurationFile argument.

Remember - Tomcat installation must be configured according to Quick Start.

aschepp/tomcat10-slf4j-logback

Tomcat + SLF4J + Logback

RELEASES

Quick Start

Maven Central Distribution

Site Page

Details

Installation

Configuration

Tomcat Customization

Tomcat 10.0.x

Using Tomcat in Eclipse