Ibrahim M. Ghazal created LOG4J2-2025:
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Summary: Support Tomcat JULI's per-webapp JUL logging by
implementing java.util.logging.Handler
Key: LOG4J2-2025
URL: https://issues.apache.org/jira/browse/LOG4J2-2025
Project: Log4j 2
Issue Type: Improvement
Components: JUL adapter
Affects Versions: 2.8.2
Environment: Tomcat 8.5.20, Oracle Java 1.8.0_144
Reporter: Ibrahim M. Ghazal
Priority: Minor
On most servlet containers, the only way to redirect JUL calls to Log4j is by
setting the
{{java.util.logging.manager=org.apache.logging.log4j.jul.LogManager}} system
property *globally*. This often breaks the native logging of the container, and
could also break other apps on the same container do not use Log4j 2. This also
requires changing the container's settings and cannot be expressed in the app
itself.
Another approach (used by slf4j) is to implement {{java.util.logging.Handler}}
and then install this handler at the root logger, either programmatically by
calling {{LogManager.getLogManager().getLogger("").addHandler(...)}} or by
changing logging.properties at the JRE level. This also breaks the container's
native logging and other apps, but in different ways than LogManager. I do not
advocate this approach, but it's useful to know about it as a background for
this feature request.
(tl;dr: It's impossible to reliably redirect JUL from a webapp without creating
a mess).
Thankfully, Tomcat has a solution for this: Tomcat
[JULI|https://tomcat.apache.org/tomcat-8.5-doc/logging.html] allows per-webapp
configuration by adding a {{WEB-INF/classes/logging.properties}} file with
{{handlers=some.custom.Handler}} inside it. This will redirect JUL calls from
this webapp (and this webapp only) to that handler, and that handler then can
redirect to Log4j.
In short: Add a {{java.util.logging.Handler}} implementation that redirects to
Log4j so that webapps can use Tomcat's per-webapp configuration and avoid the
JUL mess.
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