chjava

Changes the current Java JVM in use on macOS by changing $JAVA_HOME. If you want something more, there are tools like sdkman which do a lot more. I wanted as little as possible.

chjava just makes setting $JAVA_HOME easier than mucking about with export JAVA_HOME=$(/usr/libexec/java_home -v ...).

Why?

macOS provides a shim-like /usr/bin/java that points at one of the JDK/JRE's under /Library/Java/JavaVirtualMachines/, and which can be explicitly chosen by setting $JAVA_HOME to point at one of those. It also provides /usr/libexec/java_home for querying available JDKs, which you often see used like export JAVA_HOME=$(/usr/libexec/java_home -v 11). I have to switch the JDK I'm using a lot for different projects, and having to do the export JAVA_HOME=... dance over and over has been both tedious and error-prone.

Added to that, /usr/libexec/java_home's filtering seems a bit buggy on macOS 11 and 12. (For me, the fact filtering for x86_64 JDKs on an Apple Silicon Mac with java_home is broken was the last straw.)

Features

• Sets $JAVA_HOME
• Fuzzy matching of JDK version by version number (11 will match 11.0.8, or the latest version installed JDK 11).
• Supports picking JDK by architecture (e.g. use x86_64 on an Apple Silicon Mac).
• Supports any macOS packaged JDK/JRE installed in the standard macOS Java place.
• Does not alter $JAVA_HOME by default.
• Only alters $JAVA_HOME when run, and nothing else.
• Optionally supports auto-switching via a .java-version file.
• Supports bash and zsh.
• Small (~100 LOC).
• Has tests.
• Mostly stolen (in structure if not method) from the ruby-switching tool chruby.

Anti-features

• Does not hook cd.
• Does not install executable shims or anything like that.
• Does not require Rubies be installed into your home directory.
• Does not automatically switch Rubies by default.
• Does not require write-access to the Ruby directory in order to install gems.
• Does not install JDKs for you.

Requirements

• bash >= 3 or zsh

Install

wget -O chjava-0.0.3.tar.gz https://github.com/fidothe/chjava/archive/v0.0.3.tar.gz
tar -xzvf chjava-0.0.3.tar.gz
cd chjava-0.0.3/
sudo make install

setup.sh

chjava also includes a setup.sh script, which installs chjava and adds a zshrc/bashrc-type script into, by default, /etc/profile.d to load chjava.sh and chjava/auto.sh. Simply run the script as root or via sudo:

sudo ./scripts/setup.sh

or, if you want to specifiy where to put the rc file:

sudo .scripts/setup.sh ~/.zshrc.d/

Examples

List available JDKs:

$ chjava
   adoptopenjdk-8.jdk 1.8.0_292 [x86_64]
   zulu-11.jdk 11.0.13 [x86_64]
   zulu-17.jdk 17.0.1 [arm64]
   zulu-8.jdk 1.8.0_312 [arm64]

Select a JDK:

$ chjava 17
$ chjava
   adoptopenjdk-8.jdk 1.8.0_292 [x86_64]
   zulu-11.jdk 11.0.13 [x86_64]
 * zulu-17.jdk 17.0.1 [arm64]
   zulu-8.jdk 1.8.0_312 [arm64]
$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/zulu-17.jdk/Contents/Home

chjava ignores non-native arch JDKs by default:

$ chjava 11
chjava: unknown Java: 11
$ echo $?
1

But, you can specify the arch you want:

$ chjava 11 x86_64
$ chjava
   adoptopenjdk-8.jdk 1.8.0_292 [x86_64]
 * zulu-11.jdk 11.0.13 [x86_64]
   zulu-17.jdk 17.0.1 [arm64]
   zulu-8.jdk 1.8.0_312 [arm64]

Switch back to system default Java:

$ chjava system
$ test -z $JAVA_HOME && echo "system default"
system default

Specify by using the JDK folder's name:

$ chjava zulu-8.jdk
$ chjava
   adoptopenjdk-8.jdk 1.8.0_292 [x86_64]
   zulu-11.jdk 11.0.13 [x86_64]
   zulu-17.jdk 17.0.1 [arm64]
 * zulu-8.jdk 1.8.0_312 [arm64]

Auto-switching

If you want chjava to auto-switch $JAVA_HOME for you when you cd between projects, then source chjava/auto.sh in your .bashrc/.zshrc.

source /usr/local/share/chjava/chjava.sh
source /usr/local/share/chjava/chjava.sh

Much like chruby and other ruby auto-switchers, chjava will look for a special file, named .java-version, in the current or parent directories and switch based on it. The format is, essentially, nothing more than the arguments you'd pass to chjava in the file. These examples are all valid .java-version files.

11

11 arm64

zulu-17.jdk

Acknowledgements

Many thanks to postmodern, chruby's author, for a tool which has been an essential part of my setup for the best part of a decade.