Hi, Compiling 2.x using JDK 8 requires a lot of tricks:
* Surefire scans classes using the main Maven JDK, so we must be sure `module-info.class` and other Java 9+ classes are not on the test classpath. This basically means we need to delete them before testing and creating them afterwards. * We need toolchains even if we disable tests, * Some Maven or compiler plugins (like Error Prone) either require Java 11 or are hard to configure on Java 8. That is why I would propose to bump the JDK requirement in the POM file to JDK 11+ (for `log4j-jpl`) and add `--release 8` everywhere it makes sense. For reproducibility purposes the CI and apache-release profiles would still need to fix a JDK (JDK 17?) for compilation and a JRE (JRE 8) for testing. But a casual user will be able to run the build process without toolchains. I have a working prototype on this branch: https://github.com/ppkarwasz/logging-log4j2/tree/java17 The only problem I wasn't able to solve is to compile `log4j-jmx-gui` with JDK 11+: it requires `jconsole.jar` in the classpath, all JDK's after 8 have a module for that. I think we could move it to a separate repo. Remark that `log4j-api`, which uses `sun.reflect.Reflection`, compiles perfectly with JDK 17 and `--release 8`. Piotr
