README.md

JRuby projects with jar dependencies

examples
├── gem-with-jar-dependencies
├── gem-with-java-extension
│   ├── using-maven
│   ├── using-rake-compiler
│   └── using-ruby-maven
├── gem-with-java-extension-and-dependencies
│   ├── using-maven
│   ├── using-rake-compiler
│   └── using-ruby-maven
└── sinatra-app
    ├── having-gems-with-jar-dependencies
    └── having-jarfile-and-gems-with-jar-dependencies

to build the java extension you can do it with either proper maven, or with help of the ruby-maven gem or the rake-compiler gem.

version ranges against a picked version

jar-dependencies uses maven under the hood to resolve and install jar dependencies. maven discourages the use of version ranges and without version ranges there a deterministic version resolution, i.e. there is way to resolve conflicts in maven (see section 'Dependency mediation').

so if you use version ranges like rubygems does it, then lock down the versions of jar dependencies is needed. for this use the command

lock_jars

from the jar-dependencies plugin.

gem with jar dependencies

see the project here: gem with jar dependencies

you need to use bundler in this example. just declare the jar dependencies inside the gemspec, run

bundle install

and then you can use them with your ruby code.

with lock down of the jar versions the setup is

bundle install
lock_jars

gem with java extension

use can use maven, ruby-maven or rake-compiler to build the extension. note that there is no jar-dependencies gem involved here.

using maven

see project here: gem with java extension using maven

you need maven 3.9.x installed to get it working and the project needs to prepare maven to use the ruby DSL for maven. this is done by adding to your project. or use maven wrapper

bundle install
mvn prepare-package

to setup your project.

using ruby-maven

see project here: gem with java extension using ruby-maven

use the ruby-maven gem instead of system installed maven. much more ruby like, no need to have anything installed on the system beside jruby, i.e.

bundle install
rake compile

to setup your project.

using rake-compiler

see project here: gem with java extension using rake-compiler

just use the rake compiler inside the Rakefile, i.e.

bundle install
rake compile

to setup your project.

gem with java extension and jar dependencies

this is more since you might need the jar dependencies and its transitive dependencies for compiling the gem extension. all these examples uses the jar dependencies declaration from the gemspec file.

using maven

see project here: gem with java extension and jar dependencies using maven

maven just sets up the compile classpath for building the extension jar

setup with locked jars

bundle install
lock_jars
mvn prepare-package

using ruby-maven

see project here: gem with java extension and jar dependencies using ruby-maven

like maven but using ruby-maven instrad.

setup with locked jars

bundle install
lock_jars
rake compile

using rake-compiler

see project here: gem with java extension and jar dependencies using rake-compiler

jar-dependencies gems offers a simple way to pass on the classpath to rake-compiler.

setup with locked jars

bundle install
lock_jars
rake compile

summary

using rake-compiler or ruby-maven is no difference for the user setting up the gem.

maven is more to demostrate what is there and it allows to use a gem project as part of mutli-module maven build keeping the ruby project as ruby project but still integrate it nicely with maven.