The `core.Logger#setLevel` method should work like `Configurator#setLevel`

[ppkarwasz]

The main difference between the core.Logger#setLevel method and Configurator#setLevel is that the former changes only the level of a specific logger, while the latter also changes the level of child loggers.

As documented in its Javadoc, the core.Logger#setLevel method is not part of the public API (so it can do whatever it wants). However it is used in log4j-1.2-api and log4j-jul instead of the more correct Configurator#setLevel method and it causes those modules to misbehave.

We can therefore:

• either change the way Logger#setLevel works to match the behavior of Configurator#setLevel (IMHO it is the best option, since it prevents mistakes from committers and users),
• or simply replace Logger#setLevel with Configurator#setLevel in log4j-1.2-api and log4j-jul.

[garydgregory]

I was bitten by this issue in Apache Commons Logging.

[vy]

The main difference between the core.Logger#setLevel method and [Configurator#setLevel](https://logging.apache.org/log4j/2.x/javadoc/log4j-
We can therefore:

1. either change the way Logger#setLevel works to match the behavior of Configurator#setLevel (IMHO it is the best option, since it prevents mistakes from committers and users),
2. or simply replace Logger#setLevel with Configurator#setLevel in log4j-1.2-api and log4j-jul.

Thanks for investigation, @ppkarwasz. I would like to add a 3rd option to the list above:

3. do both (would be of my preference)

[garydgregory]

TY @ppkarwasz for helping out with #2282, merged! 👍

[ppkarwasz]

Let's leave this issue open, until we check log4j-jul.