Minor Description
I'm trying out the current `3.0.0-SNAPSHOT` (not sure if they have a unique ID, but I got them on 2023-03-03) because I want to use Log4j 2 in a project with `jlink`. I've used `api`, `core`, and (transitively) `plugins`.
I'm using programmatic configuration (no configuration file), if that matters.
When using `jlink` with the `--strip-debug` flag with Log4j 2, the resulting runtime image seems to be broken. When trying to run it, Log4j 2 immediately spits out a giant number of errors and exceptions.
It looks like the Log4j 2 components essentially can't find their own attributes, nor the attributes of other components?
(EDIT: I don't know how to do inline code formatting here.)
Here is some of the output (it's far too much to include it all):
ERROR StatusConsoleListener Appender references must contain a reference: arg0 ERROR StatusConsoleListener Could not configure plugin element AppenderRef: org.apache.logging.log4j.plugins.validation.ConstraintValidationException: Validation failed for arg0 (source: java.lang.String arg0) and value null org.apache.logging.log4j.plugins.validation.ConstraintValidationException: Validation failed for arg0 (source: java.lang.String arg0) and value null at org.apache.logging.log4j.plugins@3.0.0-SNAPSHOT/org.apache.logging.log4j.plugins.di.DefaultInjector.validate(Unknown Source) at org.apache.logging.log4j.plugins@3.0.0-SNAPSHOT/org.apache.logging.log4j.plugins.di.DefaultInjector.lambda$getArguments$37(Unknown Source) [...]
ERROR StatusConsoleListener AppenderRef contains an invalid element or attribute "ref" ERROR StatusConsoleListener Appender references must contain a reference: arg0 ERROR StatusConsoleListener Could not configure plugin element AppenderRef: org.apache.logging.log4j.plugins.validation.ConstraintValidationException: Validation failed for arg0 (source: java.lang.String arg0) and value null [...]
[...] ERROR StatusConsoleListener Logger contains invalid attributes "name", "level" ERROR StatusConsoleListener Logger has no field or parameter that matches element AppenderRef ERROR StatusConsoleListener Logger has no field or parameter that matches element AppenderRef ERROR StatusConsoleListener Skipping null child object with name Logger in element Loggers ERROR StatusConsoleListener Loggers has no field or parameter that matches element Logger ERROR StatusConsoleListener ThresholdFilter contains an invalid element or attribute "level" ERROR StatusConsoleListener ThresholdFilter contains an invalid element or attribute "level" [...]
When not using the `--strip-debug` flag, things seem to work fine.
Is this a known issue? Or even expected behavior? What is Log4j 2 doing that could be causing this? I can barely find any information about what exactly `--strip-debug` even strips from the runtime image.
Is this a problem related to reflection, possibly?
While the workaround is just not adding `--strip-debug`, this would likely trip up more people in the future. I spent almost two days until I found out that this was even the problem (which might just be my inexperience with the Java Platform Module System, though).
To reproduce this:
- Create a Java or Kotlin-JVM application that depends on Log4j 2 `3.0.0-SNAPSHOT` and that has a `module-info.java`
- Do some Log4j things in the main method, like creating a logger and logging something
- Create a runtime image from your application with `jlink`, including the `--strip-debug` flag
- Run that runtime image and observe the output