That is actually an interesting question. If you look at the logic, all the providers are loaded. They are then looped through and the first one that returns a LoggerFactory is used. I really consider this code unfinished. When I wrote it I considered supporting multiple logging implementations but I couldn’t really figure out how that would work so I just stopped after loading the first one. But in theory we could have multiple logger factories and there could be an implementation that calls each of the logging implementations.
But I have never thought of a rational reason for doing it so I’ve just left it the way it is. Ralph > On Mar 15, 2022, at 2:31 PM, Tim Perry <tim.v...@gmail.com> wrote: > > In that case, should log4j log a warning if more than one provider is > included? > > Tim > > >> On Mar 15, 2022, at 1:44 PM, Ralph Goers <ralph.go...@dslextreme.com> wrote: >> >> I would not be in favor of this change. Providers have been designed since >> day one that highest wins and it is documented - >> https://logging.apache.org/log4j/2.x/manual/extending.html#LoggerContextFactory >> >> <https://logging.apache.org/log4j/2.x/manual/extending.html#LoggerContextFactory>. >> >> >> The fact that the user was surprised may be true, but the ordering was >> intentional. If you include log4j-to-slf4j it means you want to log to >> SLF4J. In that case log4j-core shouldn’t even be present. >> >> Ralph >> >>> On Mar 14, 2022, at 4:37 AM, Piotr P. Karwasz <piotr.karw...@gmail.com> >>> wrote: >>> >>>> On Mon, Mar 14, 2022 at 10:54 AM Volkan Yazıcı <vol...@yazi.ci> wrote: >>>> Regarding your remark about providers... `Provider#getPriority()` has the >>>> following javadoc: *"Gets the priority (natural ordering) of this >>>> Provider"*, >>>> hence I would have expected it to work the same lowest-comes-first way, but >>>> apparently not – relying on your assessment here. I am also inclined to >>>> align them with the lowest-comes-first strategy, though this might have a >>>> bigger impact if there are 3rd party providers out there in the wild. Maybe >>>> others can weigh in here? >>> >>> I can provide some additional evidence supporting the necessity to >>> invert the order. At least one user on Stack Overflow was surprised >>> that after adding `log4j-core` to his project, the loggers are still >>> of type `org.apache.logging.slf4j.SLF4JLogger`: >>> >>> https://stackoverflow.com/q/70487959/11748454 >>> >>> Piotr >>
