sangrealwar / helloworld-java-9

Hello World example using Maven with Java 9

Hello World with Java 9 and Docker

A simple maven project generated from the using maven-archetype-quickstart (org.apache.maven.archetypes:maven-archetype-quickstart:1.0) and updated to declare the maven compiler source and target for Java 9.

Example Docker files are also present for building Docker images containing a JDK 9 distribution.

Pre-requisites

To experiment download the following and place in the top-level directory:

• OpenJDK build of JDK 9 for Linux x64.
• Early-access Open JDK build of JDK 9 for Alpine Linux.

Build Images and Run Containers

Build a Docker image with Alpine Linux and JDK 9:

docker build -t jdk-9-alpine -f jdk-9-alpine.Dockerfile .

Build a Docker image with Debian slim and JDK 9:

docker build -t jdk-9-debian-slim -f jdk-9-debian-slim.Dockerfile .

Run the docker image to enter into the Java REPL (jshell):

docker run -it --rm jdk-9-debian-slim

List the Java modules in JDK 9:

docker run -it --rm jdk-9-debian-slim java --list-modules

Build the simple Java application with a local distribution of JDK 9:

mvnw package

Build a Docker image containing the simple Java application based of the Docker image jdk-9-debian-slim:

docker build -t helloworld-jdk-9 -f helloworld-jdk-9.Dockerfile .

Run the java dependency tool jdeps on the application jar file:

docker run -it --rm helloworld-jdk-9 jdeps --list-deps /opt/helloworld/helloworld-1.0-SNAPSHOT.jar

Create a custom Java runtime that is small and only contains the java.base module: (See also the script create-minimal-java-runtime.sh):

docker run --rm \
  --volume $PWD:/out \
  jdk-9-debian-slim \
  jlink --module-path /opt/jdk-9/jmods \
    --verbose \
    --add-modules java.base \
    --compress 2 \
    --no-header-files \
    --output /out/target/openjdk-9-base_linux-x64

Build a Docker image containing the simple Java application based of the Docker image debian:slim and the custom Java runtime previous created:

docker build -t helloworld-jdk-9-base -f helloworld-jdk-9-base.Dockerfile .

List the modules in custom Java runtime:

docker run -it --rm helloworld-jdk-9-base java --list-modules

Run the docker images:

docker run -it --rm helloworld-jdk-9

docker run -it --rm helloworld-jdk-9-base

Compare sizes:

docker images