The runtime image

There was a time when users had to install a Java runtime environment (JRE) before they could open a Java-based application. This wasn’t only annoying for users but it could lead to version conflicts when another app wasn’t compatible with the installed JRe.

The solution: Each app should come with its own individual JRE bundled as part of the app. This solves the compatibility conflicts because each app has a compatible JRE. Such a bundled JRE is called a runtime image. Physically seen, it is a folder where the content follows a certain file structure.

The jlink tool is responsible for generating runtime images and is included in the JDK since Java 9. The plugin adds a generateRuntimeImage task to the build that produces a runtime image to be bundled with the application.

Windows

Creating a new project

gradlew.bat generateRuntimeImage

Linux

Creating a new project

./gradlew generateRuntimeImage

The runtime image is stored under build/jlink/runtime. It is an input for the next step.