Master your Java Environment with jenv

Website : http://www.jenv.be

Maintainers :

• Gildas Cuisinier

Future maintainer in discussion:

• Benjamin Berman

As he makes an incredible work by taking time to merge the Pull Request on his fork, I (@gcuisinier) am in discussion with him to take part of jEnv directly if he wants. Whatever his decision, I thank him for his work, and to have convincing me to think about the future of jEnv and accepting a new maintainer for the good of the project.

What's jEnv ?

This is an updated fork of jenv, a beloved Java environment manager adapted from rbenv.

jenv gives you a few critical affordances for using java on development machines:

• It lets you switch between java versions. This is useful when developing Android applications, which generally require Java 8 for its tools, versus server applications, which use later versions like Java 11.
• It sets JAVA_HOME inside your shell, in a way that can be set globally, local to the current working directory or per shell.

However, this project does not:

• Install java for you. Use your platform appropriate package manager to install java. On macOS, brew is recommended.

This document will show you how to install jenv, review its most common commands, show example workflows and identify known issues.

Contents

1. Getting Started
2. Example Workflows
3. Known Issues

1. Getting Started

Follow the steps below to get a working jenv installation with knowledge of your java environment. Read all the code you execute carefully: a $ symbol at the beginning of a line should be omitted, since it's meant to show you entering a command into your terminal and observing the response after the command.

1.1 Installing jenv

On macOS, you can install jEnv using Homebrew:

brew install jenv

Or if you use MacPorts on macOS:

sudo port install jenv

Alternatively, and on Linux, you can install it from source:

git clone https://github.com/jenv/jenv.git ~/.jenv

1.2 Configuring your shell

jEnv needs to be intialised in your shell by evalling the output of jenv init -. e.g.

# Shell: bash
echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bash_profile
echo 'eval "$(jenv init -)"' >> ~/.bash_profile
# Shell: zsh
echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.zshrc
echo 'eval "$(jenv init -)"' >> ~/.zshrc

To have JAVA_HOME get set by jEnv, enable the export plugin. This needs to be done in an initialised shell:

eval "$(jenv init -)"
jenv enable-plugin export

Restart your shell by closing and reopening your terminal window or running exec $SHELL -l in the current session for the changes to take effect.

exec $SHELL -l

To verify jenv was installed and initialised, run jenv doctor. On a macOS machine, you'll observe the following output:

$ jenv doctor
[OK]	No JAVA_HOME set
[ERROR]	Java binary in path is not in the jenv shims.
[ERROR]	Please check your path, or try using `jenv add /path/to/java/home`
	PATH : /Users/user/.jenv/libexec:/Users/user/.jenv/shims:/Users/user/.jenv/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
[OK]	Jenv is correctly loaded

Observe that jenv is correctly loaded but Java is not yet installed. To rememedy this, see "Adding Your Java Environment" below.

Problem? Please visit the Trouble Shooting Wiki page.

Support for fish

Untested: While this fork has improved fish shell support, it has not been tested by this maintainer. To install jenv for Fish according to the contributor's instructions:

echo 'set PATH $HOME/.jenv/bin $PATH' >> ~/.config/fish/config.fish
echo 'status --is-interactive; and jenv init - | source' >> ~/.config/fish/config.fish
cp ~/.jenv/fish/jenv.fish ~/.config/fish/functions/jenv.fish

1.3 Adding Your Java Environment

Use jenv add to inform jenv where your Java environment is located. jenv does not, by itself, install Java.

For example, on macOS, use brew to install the latest Java (OpenJDK 21, also follow the caveat steps to symlink into the system virtual machines) followed by the appropriate jenv add PATH_TO_JVM_HOME command to recognize it.

brew install java
sudo ln -sfn /usr/local/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk
jenv add "$(/usr/libexec/java_home)" # this will always default to the latest version in /Library/Java/JavaVirtualMachines
# or
# jenv add /Library/Java/JavaVirtualMachines/openjdk.jdk

With macOS OpenJDK 21.0.2 installed, for example, either of these commands will add /Library/Java/JavaVirtualMachines/openjdk.jdk/Contents/Home as a valid JVM. Your JVM directory may vary!

Observe now that this version of Java is added to your jenv versions command:

$ jenv versions
* system (set by /Users/user/.jenv/version)
  21.0
  21.0.2
  openjdk64-21.0.2

By default, the latest version of Java is your system Java on macOS.

We'll now set a jenv local VERSION local Java version for the current working directory. This will create a .java-version file we can check into Git for our projects, and jenv will load it correctly when a shell is started from this directory.

$ jenv local 21.0.2
$ cat .java-version
21.0.2

Is JAVA_HOME set?

$ echo ${JAVA_HOME}
/Users/bberman/.jenv/versions/21.0.2

Yes! Observe that JAVA_HOME is set to a valid shim directory - this is a result of enabling the export plugin.

If you executed this commands inside your $HOME directory, you can now delete .java-version:

jenv local --unset
# or
rm .java-version

1.4 Setting Java versions

jenv can set Java versions at 3 levels:

• global (lowest priority)
• local
• shell (highest priority)

Where multiple versions are set, the highest priority setting as above takes effect.

For example if the global version was 17 and the shell version was 11, 11 would be used.

1.4.1 Setting a Global Java Version

Use jenv global VERSION to set a global, default Java version:

jenv global 21.0.2

When you next open a shell or terminal window, this version of Java will be the default.

On macOS, this sets JAVA_HOME for GUI applications on macOS using jenv macos-javahome. Integrates this tutorial to create a file that does not update dynamically depending on what local or shell version of Java is set, only global.

It can be unset with

jenv global --unset

1.4.2 Setting a local Java Version

Use jenv local VERSION to set the Java used in this folder.

This version will activate whenever you cd into the follder. This is useful in the root of projects, for example where you would typically run a ./gradlew build or ./mvnw package command from.

jenv local 21.0.2

This can be unset with

jenv local --unset
# or
unset .java-version

1.4.3 Setting a Shell Java Version

Use jenv shell VERSION to set the Java used in this particular shell session:

jenv shell 21.0.2

This can be unset with

jenv shell --unset
# or
unset JENV_VERSION

2 Common Workflows

These common workflows demonstrate how to use jenv to solve common problems.

2.1 Using Two JVMs on macOS

Our goal is to have both the latest version of Java and JDK 8 installed at the same time. This is helpful for developing Android applications, whose build tools are sensitive to using an exact Java version.

We'll resume where we left off with Java 21.0.2 installed. Let's install Java 8 from brew and symlink it into the Library folder per the caveats.

brew install openjdk@8
sudo ln -sfn /usr/local/opt/openjdk@8/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk-8.jdk

This will install the latest version of Java 8 to a special directory in macOS. Let's see which directory that is:

$ ls -1 /Library/Java/JavaVirtualMachines 
openjdk-8.jdk
openjdk.jdk

Observe the openjdk-8.jdk directory. Your exact version may vary. We cannot retrieve this using /usr/libexec/java_home, unfortunately. We'll add the Java home directory using jenv so that it shows up in our jenv versions command:

$ jenv add /Library/Java/JavaVirtualMachines/openjdk-8.jdk/Contents/Home/
openjdk64-1.8.0.222 added
1.8.0.222 added
1.8 added
$ jenv versions
* system
  1.8
  1.8.0.222
  openjdk64-1.8.0.222
  21
  21.0
  21.0.2
  openjdk64-21.0.2

2.2 Other Workflows

Please contribute your own using a pull request!

3 Known Issues

Users seem to have issues using jenv with Fish. Please report any here.