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https://github.com/wkgcass/jdkman

Manage multiple JDK instances.
https://github.com/wkgcass/jdkman

command-line-tool java native-image

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Manage multiple JDK instances.

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README 

        
# jdkman



## What is `jdkman`



`jdkman` is a command line tool which helps you manage multiple JDK instances.



[An asciinema cast](https://asciinema.org/a/625934) shows how to use `jdkman`.  

[This video](https://www.bilibili.com/video/BV1Gu4y137cg/) shows how to configure `jdkman` on Windows.



## How to install



### 1. Download



Download the pre-built binary from the [release page](https://github.com/wkgcass/jdkman/releases).  

You will need to download the binary corresponding to your operating system and cpu architecture.



Rename the downloaded file `jdkman-$os-$arch` to `jdkman`  

You will also need to run `chmod +x jdkman` on Linux or macOS.



### 2. Configure



#### bash or zsh



Add the following lines in your `~/.bashrc` or `~/.bash_profile` or `~/.zshrc`



```shell

## add jdkman to your PATH environment variable.

export PATH="$PATH:/path/to/jdkman"

eval "`jdkman init sh`"

```



#### Powershell



Add `\path\to\jdkman` to your PATH environment variable.



Then configure the profile script by entering the following lines in powershell:



```powershell

echo $profile ## show the profile script location

New-Item -ItemType Directory -Path (Split-Path $profile) -Force

'Invoke-Expression -Command (jdkman init pwsh)' | Out-File -FilePath $profile -Append

```



#### Windows cmd



Since cmd doesn't support `eval` nor `source`, there's very little that `jdkman` could provide.



Add `\path\to\jdkman` to your PATH environment variable.  

Add `\YourHomePath\jdkman-scripts` to your PATH environment variable.



Then in cmd, run once (for each time you upgrades `jdkman`):



```cmd

jdkman init

```



> You can ignore the init output.



## How to use



### 1. Add JDKs



```shell

jdkman add /Library/Java/JavaVirtualMachines/jdk-21.jdk/Contents/Home

```



### 2. Show JDKs



```shell

jdkman list

```



### 3. Set JDK version for each project



Add a file `.java-version` in the root directory of your project with the following content:



```

21

```



`21` could be changed to any JDK versions, e.g. `11`, `11.0.2`, `1.8`.  

`jdkman` will find the most appropriate JDK version for you.



You could also specify the `implementor` (or `vendor`) of the JDK:  

Specify the vendor name, add a colon, then specify the jdk version:



```

Oracle Corporation:21.0.1+12-29

```



### 4. Use java



```shell

java -version

echo $JAVA_HOME

```



### 5. The `cd` command and `JAVA_HOME`



For `bash|zsh|powershell`, the `cd` command is replaced with a convenient function: `cdjh`  

it will `cd` into the specified directory, and configure `JAVA_HOME` environment variable automatically.



You could also instead explicitly call the `cdjh` function.



Note: This feature is not provided for `cmd`, you have to set it manually by executing the following command:  

```cmd

for /f "delims=" %%i in ('jdkman which') do set "JAVA_HOME=%%i"

```



## How to build



### 1. Prerequisites



* JDK 21

* GraalVM Native Image for JDK 21



To build `jdkman-proxy`, you will need `rust|cargo`.  

It's already built and placed in resource folder, so you can skip `rust`.



### 2. Build



#### Linux or macOS



```shell

./gradlew clean shadowJar

native-image \

	--enable-preview \

	-jar build/libs/jdkman.jar \

	-Ob -march=compatibility \

	--no-fallback \

	-o jdkman

```



#### Windows (using powershell)



```powershell

# build `jdkman-proxy`

$arch="x86_64" # change to aarch64 if running arm windows

cd .\src\main\rust\

cargo build --release

Copy-Item .\target\release\jdkman-proxy.exe ..\resources\io\vproxy\jdkman\res\jdkman_proxy-windows-$arch.exe

cd ..\..\..\



# build jdkman

.\gradlew.bat clean shadowJar

native-image `

	--enable-preview `

	-jar build\libs\jdkman.jar `

	--features=io.vproxy.jdkman.res.Feature `

	--static `

	-Ob -march=compatibility `

	--no-fallback `

	-o jdkman

```



#### Linux static image in docker



You can build a linux static native image using `vproxyio/graalvm-jdk-21`



```shell

docker run --name jdkman-build -it -v `pwd`:/workdir vproxyio/graalvm-jdk-21 /bin/bash

## inside docker

./gradlew clean shadowJar

LIBC="musl" ## or glibc

native-image \

	--enable-preview \

	-jar build/libs/jdkman.jar \

	--static --libc=$LIBC \

	-Ob -march=compatibility \

	--no-fallback \

	-o jdkman

```