You are correct that log4j-to-jul routes the log4j2 API to java.util.logging.
When using log4j-to-jul you cannot use ANY other log4j modules except for
log4j-api. You must configure Tomcat’s logging to handle all the logging for
your application.
Ralph
> On Jun 2, 2023, at 3:13 PM, Jason Guild <jason.gu...@alaska.gov> wrote:
>
> Hi All:
>
> I have a web application that uses log4j (v2.20) which runs inside Tomcat 9.x
> on Java 8.
>
> Currently, the WEB-INF/log4j2.xml configuration file in the application sends
> its output to a rolling file appender targeting a separate file on the file
> system, but what I'd like to do is make all log4j output go to the regular
> per-application log under ${catalina_base}/logs which is managed by the stock
> Tomcat JULI implementation.
>
> We now have the log4j-to-jul module which can adapt log4j 2 output back to
> java.util.logging.
> Similar to my understanding of the purpose for log4j-to-slf4j, it seems that
> log4j-to-jul is meant to be used as an implementation by itself for log4j-api
> and without log4j-core.
>
> The application currently uses log4j-web to get the all the essential setup
> for initializing log4j 2 under an application container. The log4j-web
> library appears to have a hard dependency on log4j-core.
>
> After adding log4j-to-jul to the application classpath, I can see that it is
> recognized:
>> Multiple logging implementations found:
>> Factory: org.apache.logging.log4j.core.impl.Log4jContextFactory, Weighting:
>> 10
>> Factory: org.apache.logging.log4j.tojul.JULLoggerContextFactory, Weighting:
>> 20
>
> But then the following error is reported:
>> ERROR StatusLogger LogManager returned an instance of
>> org.apache.logging.log4j.tojul.JULLoggerContextFactory which does not
>> implement org.apache.logging.log4j.core.impl.Log4jContextFactory. Unable to
>> initialize Log4j.
>
> In org.apache.logging.core.config.Configurator, line 47 there is a
> conditional that checks the return type of the logging implementation is-a
> Log4jContextFactory. The problem is then that JULLoggerContextFactory
> implements only LoggerContextFactory.
>
> I'd like to keep my tomcat container as stock as possible. Particularly,
> continuing to use the built-in JULI per-application logging and *not*
> switching the entire container to use log4j as its logging implementation.
>
> Can anyone suggest how I can use log4j-to-jul successfully for my use case?
>
> Thanks,
> Jason
>
>
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