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Java 9 - JPMS (Java Platform Module System) + Maven + IntelliJ

This is a sandbox app created to test out Java 9' Project Jigsaw with Maven functionality.

For Project Jigsaw, without maven, check this tutorial: http://openjdk.java.net/projects/jigsaw/quick-start

For reference, I have also added Java 8 app to do the similar thing.

I have used simple Java Reflection API and not the ServiceLoader since I wanted to pass parameters and not use default constructors or Abstract Factories.

Experiment

  • Created an interface Shape
  • Created two implementations class Circle and class Square of interface Shape.
  • Main App should have compile-time dependency on interface Shape, but runtime dependency on implementations.

Modules

  1. API
    • Module which has interface Shape and default implementation class Square.
  2. IMPL
    • Module has compile-time dependency on API.
    • This module has class Circle which has custom implementation of interface Shape.
  3. APP
    • This module has the Main class.
    • It will use class ShapeFactory in API, which will create objects of Circle and Square using Java Reflection API (wanted to keep things simple and avoid any dependency injection libs/frameworks).
    • Try to uncomment the lines which are trying to use Circle and Square classes at compile-time. It should give a compile-time error.

Dependencies

[APP] ---- (compile-time) ----> [API] <---- (compile-time) ---- [IMPL]
   \                                                             ^
    \_________________________ (runtime) _______________________/

Building via Maven

mvn clean package

Maven Toolchain settings

Add this in ~/.m2/toolchains.xml

<?xml version="1.0"?>
<toolchains>
  <toolchain>
    <type>jdk</type>
    <provides>
      <version>1.9</version>
      <vendor>oracle</vendor>
    </provides>
    <configuration>
      <jdkHome>/path/to/java-9/home</jdkHome>
    </configuration>
  </toolchain>
</toolchains>

Running from IntelliJ

Java9's JPMS do not work on IntelliJ 2017.2.*

You need IntelliJ with version 2017.3 or later.

You may need to explicitly change the module SDKs to Java9.