Emulate effects of j.u.l.Logger.setLevel

[ppkarwasz]

Some libraries rely on j.u.l.Logger.getLevel returning the value that was set using j.u.l.Logger.setLevel.

This PR changes #2353 so that:

• By default, the effective configuration of the logging backend is not modified by log4j-jul.
• Calling setLevel modifies the return value of getLevel. Both these methods should not be used in user code, because the effective level of a logger should be checked with j.u.l.isLoggable instead. Therefore, I don't see any potential problems with these modifications.

Closes #3119

[ppkarwasz]

Anticipating other similar problems with the j.u.l.Logger methods, what do you think about implementing in term of "WARN + super" also the: setFilter, addHandler, removeHandler, setUseParentHandler? We can still keep the current implementation for setParent (throwing).

The setResourceBundle method, on the other hand, should probably be implemented differently: after it is called, we need to replace the message factory used by the JUL bridge with one the uses the specified bundle.

[ppkarwasz]

@kangarko,

Can you check if the latest 2.25.0-SNAPSHOT solves your problem with Nashorn? The URL of our Maven snapshot repository is on our download page.

[kangarko]

@ppkarwasz appreciated it, unfortunately we rely on the Velocity software which uses said library, I found out the problem started since of this commit: PaperMC/Velocity@f2d6e14

I do not see them using log4j2, my question is can I do something on my end? I am essentially developing a plugin for velocity which can add libraries to Velocity classpath, so I think I have some options on my end too. Thanks!

[kangarko]

@ppkarwasz could you please provide nashorn-core snapshot, instead? Because production is affected since October, I could just use the snapshot for now. Many thanks.

[ppkarwasz]

@kangarko,

I am not a Nashorn maintainer, sorry.

PaperMC does use log4j-jul: see the libs.version.toml file. You need to bump the version to 2.25.0-SNAPSHOT and recompile.

[kangarko]

Gotcha, thanks for the that, I have passed them the relevant information. I am unfortunately not a Paper maintainer either.

[ppkarwasz]

@kangarko,

The workaround for this bug was provided by the reporter in this comment:

The solution for now is to set

-Dlog4j2.julLoggerAdapter=org.apache.logging.log4j.jul.CoreLoggerAdapter

You can de facto apply that right now on prod.

[kangarko]

@ppkarwasz Thank you, you made my day with this fix!!!

I will add a note to our customers so that they can adjust their server system properties for now.