Import JRuby's stringio impl

.github/workflows/ubuntu.yml

@@ -12,7 +12,7 @@ jobs:
         os:
         - ubuntu-20.04
         - ubuntu-18.04
-        ruby: [ '3.0', '2.7', '2.6', 'debug', 'head' ]
+        ruby: [ '3.0', '2.7', '2.6', 'debug', 'head', 'jruby-head' ]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Ruby
@@ -22,3 +22,5 @@ jobs:
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically
     - name: Run test
       run: bundle exec rake
+    - name: Build gem
+      run: gem install rake-compiler && rake build

.gitignore

@@ -11,4 +11,5 @@
 *.bundle
 *.dll
 *.so
+*.jar
 Makefile

Gemfile

@@ -3,4 +3,8 @@ source "https://rubygems.org"
 gemspec
 
 gem 'rake-compiler'
-gem 'test-unit'
+
+group :development do
+  gem 'test-unit'
+  gem 'ruby-maven', :platforms => :jruby
+end

Rakefile

@@ -3,9 +3,19 @@ require "rake/testtask"
 
 name = "stringio"
 
-require 'rake/extensiontask'
-extask = Rake::ExtensionTask.new(name) do |x|
-  x.lib_dir << "/#{RUBY_VERSION}/#{x.platform}"
+if RUBY_PLATFORM =~ /java/
+  require 'rake/javaextensiontask'
+  extask = Rake::JavaExtensionTask.new("stringio") do |ext|
+    require 'maven/ruby/maven'
+    ext.source_version = '1.8'
+    ext.target_version = '1.8'
+    ext.ext_dir = 'ext/java'
+  end
+else
+  require 'rake/extensiontask'
+  extask = Rake::ExtensionTask.new(name) do |x|
+    x.lib_dir << "/#{RUBY_VERSION}/#{x.platform}"
+  end
 end
 Rake::TestTask.new(:test) do |t|
   ENV["RUBYOPT"] = "-I" + [extask.lib_dir, "test/lib"].join(File::PATH_SEPARATOR)