README.md

Introduction

This is the documentation page for the Java wrapper of OR-Tools.

This project aim to explain how you build a Java 1.8 native (for win32-x86-64, linux-x86-64 and darwin-x86-64) maven multiple package using mvn and few POM.xml.

Table of Content

• Requirement
• Directory Layout
• Build Process
  • Local Package
  • Building a native Package
  • Building a Local Package
  • Testing the Local Package
• Appendices
  • Resources
• Misc

Requirement

You'll need a "Java SDK >= 1.8" and "Maven >= 3.6".

Directory Layout

• pom-native.xml.in POM template to build the native project.
• com/google/ortools/Loader.java Helper to unpack and load the correct native libraries.
• pom-local.xml.in POM template to build the "pure" Java project.
• pom-sample.xml.in POM template used to build samples and examples.
• pom-test.xml.in POM template used to build tests.

Build Process

To Create a native dependent package we will split it in two parts:

• A bunch of com.google.ortools:ortools-{platform} maven packages for each supported platform targeted and containing the native libraries.
• A java maven package com.google.ortools:ortools-java depending on the native package and containing the Java code.

platform names come from the JNA project (Java Native Access) which will be use to find at runtime on which platform the code is currently running.

Local Package

The pipeline for linux-x86-64 should be as follow:
note: The pipeline will be similar for darwin-x86-64 and win32-x86-64 architecture, don't hesitate to look at the CI log!

Building local native Package

Thus we have the C++ shared library libortools.so and the SWIG generated JNI wrappers libjniortools.so.

So first let's create the local com.google.ortools:ortools-{platform}.jar maven package.

Here some dev-note concerning this POM.xml.

• This package is a native package only containing native libraries.

Then you can generate the package and install it locally using:

mvn package
mvn install

note: this will automatically trigger the mvn compile phase.

If everything good the package (located in <buildir>/java/ortools-<platform>/target/) should have this layout:

{...}/target/ortools-<platform>-1.0.jar:
\- <platform>
   \-libortools.so.8.0
   \-libjniortools.so
...

note: <platform> could be linux-x86-64, darwin-x86-64 or win32-x86-64.

tips: since maven package are just zip archive you can use unzip -l <package>.jar to study their layout.

Building local Package

So now, let's create the local com.google.ortools:ortools-java.jar maven package which will depend on our previous native package.

Here some dev-note concerning this POM.xml.

• Add runtime dependency on each native package(s) availabe:

  <dependency>
    <groupId>com.google.ortools</groupId>
    <artifactId>ortools-linux-x86-64</artifactId>
    <version>[8.0,)</version>
    <type>jar</type>
    <scope>runtime</scope>
  </dependency>

  • Add dependency to jna so we can find at runtime the current <platform>:

  <dependency>
    <groupId>net.java.dev.jna</groupId>
    <artifactId>jna-platform</artifactId>
    <version>5.5.0</version>
  </dependency>

Then you can generate the package using:

mvn package
mvn install

If everything good the package (located in <buildir>/java/ortools-java/target/) should have this layout:

{...}/target/ortools-java-8.0.jar:
\- com/
   \- google/
      \- ortools/
         \- Loader$PathConsumer.class
         \- Loader$1.class
         \- Loader.class
         \- constraintsolver/
            \- RoutingModel.class
            \- RoutingIndexManager.class
            \- ...
         \- ...
...

Testing local Package

We can test everything is working by using any sample project.

First you can build it using:

cmake --build build

note: ortools-java which is locally installed in the local maven cache (~/.m2/repository/com/google/ortools/ortools-java/...).

Then you can run it using:

cmake --build build --target test

or manually using:

cd <builddir>/java/component/example
mvn compile
mvn exec:java

Appendices

Few links on the subject...

Resources

• POM.xml reference
• Maven Central POM requirement
• Maven Javadoc Plugin
• Maven Source Plugin
• Maven GPG Plugin
• Java Native Access Project

Misc

Image has been generated using plantuml:

plantuml -Tsvg doc/{file}.dot

So you can find the dot source files in doc.