Minimalistic Java Modules Example

This repo contains dead simple example with 3 modules: api, provider and consumer. After building, all modules are linked with jlink and packed into a slim docker image without jre or jdk. Using jlink is an absolutely optional step. A normal java application can be found in dist folder.

To follow, see jigsaw guide.

The jlink gives us docker image with incredible 50Mb size. As soon as openjdk:X-jdk-alpine is released, size can be less than 40Mb. Note that jlink creates statically linked application, therefore you must forget about cross-platform java applications and go with docker all the way from build to deploy.

Build

Building java app with installed jdk (requires Java >= 9)

$ ./build.sh

Building docker image without jdk installed (requires Docker >= 1.17)

$ docker build . -t example

Building with installed jdk and add to docker image without jdk (don't do this unless you on linux)

$ ./build.sh
$ docker build -f Dockerfile.wrap . -t example

Run

Running module app with dependencies in dist folder (pretty much like before with classpath)

java --module-path dist -m app

Running jlink runtime image (no jre needed)

image/bin/java -m app/io.b3.app.Main

Running docker image

$ docker run --rm example

Building alpine Early-Access Build

1. Download jdk early-access build for Alpine Linux from http://jdk.java.net/11/
2. Unpack the archive to jdk-alpine folder
3. Build jdk-alpine docker image docker build -f Dockerfile.ea . -t jdk-alpine
4. Build app docker image docker build -f Dockerfile.alpine . -t hi

UPDATES

• There is Alpine Linux JDK 11 available on JDK 11 Early-Access Builds page.
• There is an official project to provide a port of the JDK to the Alpine Linux.
• The image with jdk9-apline was canceled, but we will probably get alpine image with jdk10 after April 2018.