fix: #422 prevent export hook setting JAVA_HOME when system

[andrewflbarnes]

Fixes #369, fixes #422, fixes #295 and some formatting - follow up to #350

Mac

Available JVMs

$ ls /Library/Java/JavaVirtualMachines/; /usr/libexec/java_home 
jdk1.8.0_191.jdk        openjdk-11.jdk          openjdk-8.jdk           openjdk.jdk
/usr/local/Cellar/openjdk/21.0.2/libexec/openjdk.jdk/Contents/Home

Global/defaullt system

$ jenv version; jenv info java; jenv which java; echo $JAVA_HOME; jenv javahome; java -version
system (set by /Users/andrew.barnes/.jenv-test/version)
Jenv will exec : /usr/bin/java  
Exported variables :
  JAVA_HOME=/usr/local/Cellar/openjdk/21.0.2/libexec/openjdk.jdk
/usr/bin/java
/usr/local/Cellar/openjdk/21.0.2/libexec/openjdk.jdk
/usr/local/Cellar/openjdk/21.0.2/libexec/openjdk.jdk
openjdk version "21.0.2" 2024-01-16
OpenJDK Runtime Environment Homebrew (build 21.0.2)
OpenJDK 64-Bit Server VM Homebrew (build 21.0.2, mixed mode, sharing)

Shell 1.8

$ jenv version; jenv info java; jenv which java; echo $JAVA_HOME; jenv javahome; java -version
1.8 (set by JENV_VERSION environment variable)
Jenv will exec : /Users/andrew.barnes/.jenv-test/versions/1.8/bin/java  
Exported variables :
  JAVA_HOME=/Users/andrew.barnes/.jenv-test/versions/1.8
/Users/andrew.barnes/.jenv-test/versions/1.8/bin/java
/Users/andrew.barnes/.jenv-test/versions/1.8
/Users/andrew.barnes/.jenv-test/versions/1.8
openjdk version "1.8.0_402"
OpenJDK Runtime Environment (build 1.8.0_402-bre_2024_03_05_05_38-b00)
OpenJDK 64-Bit Server VM (build 25.402-b00, mixed mode)

Ubuntu

Note: run in docker with export JENV_ROOT=/.jenv

Available JVMs

# ls /usr/lib/jvm; update-alternatives --display java
java-1.21.0-openjdk-amd64  java-21-openjdk-amd64  openjdk-21
java - auto mode
  link best version is /usr/lib/jvm/java-21-openjdk-amd64/bin/java
  link currently points to /usr/lib/jvm/java-21-openjdk-amd64/bin/java
  link java is /usr/bin/java
  slave java.1.gz is /usr/share/man/man1/java.1.gz
/usr/lib/jvm/java-21-openjdk-amd64/bin/java - priority 2111
  slave java.1.gz: /usr/lib/jvm/java-21-openjdk-amd64/man/man1/java.1.gz

Global/default system

# jenv version; jenv info java; jenv which java; echo $JAVA_HOME; jenv javahome; java -version
system (set by /.jenv/version)
Jenv will exec : /usr/bin/java  
Exported variables :
  JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64
/usr/bin/java
/usr/lib/jvm/java-21-openjdk-amd64
/usr/lib/jvm/java-21-openjdk-amd64
openjdk version "21.0.2" 2024-01-16
OpenJDK Runtime Environment (build 21.0.2+13-Ubuntu-122.04.1)
OpenJDK 64-Bit Server VM (build 21.0.2+13-Ubuntu-122.04.1, mixed mode, sharing)

Shell 21

# jenv version; jenv info java; jenv which java; echo $JAVA_HOME; jenv javahome; java -version
21 (set by JENV_VERSION environment variable)
Jenv will exec : /.jenv/versions/21/bin/java  
Exported variables :
  JAVA_HOME=/.jenv/versions/21
/.jenv/versions/21/bin/java
/.jenv/versions/21
/.jenv/versions/21
openjdk version "21.0.2" 2024-01-16
OpenJDK Runtime Environment (build 21.0.2+13-Ubuntu-122.04.1)
OpenJDK 64-Bit Server VM (build 21.0.2+13-Ubuntu-122.04.1, mixed mode, sharing)