Using jlink to deploy native(*) Java applications
A demo of using Java 9 modularization, and the JDK's new jlink tool, for zero-dependency
deployments. That is, application bundles suitable for native(*) execution, with the Java runtime
embedded.
Unlike older
approaches,
which required embedding basically an entire JRE (around 200+ megs), the jlink tool allows you to
strip down the embedded runtime to include only those portions of the standard library that are
absolutely necessary.
(*) No, this is not "native" in the C/C++ sense of AOT compilation. There is still a Java Runtime Environment executing the code. However, the code is packaged up into a deployable bundle, with a JRE and launch script native to the specific target platform (i.e. UNIX shell or Windows batch). No other software needs to be installed, and the end user experience is no different from an application shipping with Qt or GTK shared libs.
Results
This repository contains a Gradle multi-project setup, with two sub-projects. One is a basic "Hello World" command-line application, and the other a JavaFX app. These are the resulting sizes of the native application bundles that are generated, both raw as well as after being compressed with 7-zip, on a 64-bit Windows system (with Electron for comparison):
| App | Compressed with 7-zip | Raw Size when deployed |
|---|---|---|
cli (command-line application) |
10.8 MB | 21.7 MB |
gui (JavaFX desktop application) |
29.1 MB | 45.8 MB |
| electron-quick-start example | 32.8 MB | 131 MB |
How to Build
To run these Gradle commands, your system must have a JAVA_HOME environment variable pointing to a
Java 9+ location (the JDK subdirectory, not the JRE one).
gradlew linkAll
To build the command-line version or the JavaFX version separately, use:
gradlew cli:link
gradlew gui:link
You can find the output under the cli/build/dist and/or gui/build/dist subdirectories.
Each bundle will have a /bin subdirectory, containing UNIX shell scripts or Windows batch files with
the same name as the subproject (e.g. cli, gui.bat).
The contents of either dist subdirectory can be copied and run anywhere (assuming the same platform
type as the machine on which the bundle was made). You could also use any installer tool of your
choice to make a one-click installer artifact.