Tomcat common class loader not working as expected - elasticsearch

Question

I'm trying to build a Docker image of Tomcat that uses Elastic logging. I followed the ECS Logging Java Reference documentation and added the required jars to $CATALINA_HOME/lib, however, it seems that the classes are not loaded by Tomcat.
Tomcat's class loader documentation states the following about the common class loader:
This class loader contains additional classes that are made visible to both Tomcat internal classes and to all web applications.
Normally, application classes should NOT be placed here. The locations searched by this classloader are defined by the common.loader property in $CATALINA_BASE/conf/catalina.properties. The default setting will search the following locations in the order they are listed:
unpacked classes and resources in $CATALINA_BASE/lib
JAR files in $CATALINA_BASE/lib
unpacked classes and resources in $CATALINA_HOME/lib
JAR files in $CATALINA_HOME/lib
If I understand the above correctly, placing the jars in $CATALINA_HOME/lib should be enough for the common loader to find them. However the logging is not formatted by the Elastic formatter.
As a workaround I added a setenv.sh file with a CLASSPATH variable that points to the jars I added. The logging is then printed correctly in ECS format.
Can someone please explain to me how I can get this to work without using the workaround and make use of the common class loader instead?
Below is my Dockerfile:
FROM tomcat:9-jre17
COPY conf/logging.properties conf/logging.properties
COPY lib/ecs-logging-core-1.5.0.jar lib/ecs-logging-core.jar
COPY lib/jul-ecs-formatter-1.5.0.jar lib/jul-ecs-formatter.jar
COPY lib/logback-ecs-encoder-1.5.0.jar lib/logback-ecs-encoder.jar
# Workaround
COPY bin/setenv.sh bin
RUN chmod +x bin/setenv.sh
EXPOSE 8080
CMD ["catalina.sh", "run"]
This is my logging.properties file:
handlers = java.util.logging.ConsoleHandler
.handlers = java.util.logging.ConsoleHandler
java.util.logging.ConsoleHandler.level = INFO
java.util.logging.ConsoleHandler.formatter = co.elastic.logging.jul.EcsFormatter
co.elastic.logging.jul.EcsFormatter.serviceName = tomcat
java.util.logging.ConsoleHandler.encoding = UTF-8
And this is the setenv.sh file that I use as a workaround, but that I would like to get rid of:
#!/bin/sh
export CLASSPATH="/usr/local/tomcat/lib/ecs-logging-core.jar:/usr/local/tomcat/lib/jul-ecs-formatter.jar:/usr/local/tomcat/lib/logback-ecs-encoder.jar"
The result that I'm expecting looks like this:
{"#timestamp":"2022-11-28T12:29:43.276Z","log.level": "INFO","message":"Server version name: Apache Tomcat/9.0.69","ecs.version": "1.2.0","service.name":"tomcat","event.dataset":"tomcat","process.thread.name":"main","log.logger":"org.apache.catalina.startup.VersionLoggerListener"}
But the result that I'm getting without adding setenv.sh looks like this:
2022-11-28 13:44:20 Nov 28, 2022 12:44:20 PM org.apache.catalina.startup.VersionLoggerListener log
2022-11-28 13:44:20 INFO: Server version name: Apache Tomcat/9.0.69