Bug 2020478

Setting of JAVA_HOME is overwritten by mvn.

/usr/bin/mvn is a script that sources /etc/java/maven.conf which overrides JAVA_HOME. If maven-openjdk11 is installed then this is Java 11, if maven-openjdk17 is installed it is Java 17 regardless of the user's setting of JAVA_HOME.

This means that the compilation of a Java source file with features incompatible with the version set in /etc/java/maven.conf will fail.

e.g:
1. install maven-openjdk11
3. use 'alternatives' to set java to java 17 (JAVA_HOME set to /usr/lib/jvm/java-17-openjdk-17.0.1.0.12-1.rolling.fc35.x86_64)
4. Attempt to use maven to compile Java that has Java 17 features
5. Compilation fails

If MAVEN_SKIP_RC environment variable is set then /etc/mavenrc, /etc/mavenrc and "$HOME/.mavenrc" are ignored. This will mean that JAVA_HOME is not overwritten but maven may then run with a (possible) incompatible version. (setting JAVA_HOME in 
"$HOME/.mavenrc" will also do this)

In /usr/bin/mvn, maven is run with the java specified in JAVACMD.

if [ -z "$JAVA_HOME" ] ; then
  JAVACMD=`which java`
else
  JAVACMD="$JAVA_HOME/bin/java"
fi
It looks to me that a better solution is to set JAVACMD to specific Java version of the installed maven libraries (e.g. 11) and leave alone JAVA_HOME so that the user java files are compiled as expected.