Issues loading java class into gem in JRuby

Question

I am trying to add JRuby support to my C-extension gem, by writing a Java class and executing it when the gem is installed on JRuby. The code in question lives on this branch, with the important files being the java class and the code to load it when used in JRuby

At this point, I am just trying to ensure I have my gem configured correctly, and fully expect it to fail the specs.

When I try to run rspec (or the gem in IRB for that matter) I get the following backtrace

NameError: cannot load Java class com.dockyard.PgArrayParser
  get_proxy_or_package_under_package at org/jruby/javasupport/JavaUtilities.java:54
                      method_missing at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/site_ruby/shared/builtin/javasupport/java.rb:51
                       PgArrayParser at /Users/dan/Projects/dockyard/pg_array_parser/lib/pg_array_parser.rb:6
                              (root) at /Users/dan/Projects/dockyard/pg_array_parser/lib/pg_array_parser.rb:3
                             require at org/jruby/RubyKernel.java:1033
                             require at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36
                              (root) at /Users/dan/Projects/dockyard/pg_array_parser/lib/pg_array_parser.rb:2
                             require at org/jruby/RubyKernel.java:1033
                             require at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36
                              (root) at /Users/dan/Projects/dockyard/pg_array_parser/lib/pg_array_parser.rb:1
                             require at org/jruby/RubyKernel.java:1033
                             require at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36
                              (root) at /Users/dan/Projects/dockyard/pg_array_parser/spec/spec_helper.rb:1
                                load at org/jruby/RubyKernel.java:1058
                     load_spec_files at /Users/dan/Projects/dockyard/pg_array_parser/spec/parser_spec.rb:746
                             collect at org/jruby/RubyArray.java:2331
                     load_spec_files at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/gems/1.8/gems/rspec-core-2.10.1/lib/rspec/core/configuration.rb:746
                                 run at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/gems/1.8/gems/rspec-core-2.10.1/lib/rspec/core/command_line.rb:22
                                 run at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/gems/1.8/gems/rspec-core-2.10.1/lib/rspec/core/runner.rb:69
                             autorun at /Users/dan/.rbenv/versions/jruby-1.6.7.2/lib/ruby/gems/1.8/gems/rspec-core-2.10.1/lib/rspec/core/runner.rb:10
                                call at org/jruby/RubyProc.java:270
                                call at org/jruby/RubyProc.java:224

Sébastien Le Callonnec · Accepted Answer · 2012-09-03 17:58:37Z

1

Having recently worked on a JRuby extension myself, here are some of the gotchas which I have found through experiment -- and which seem to cause you problems too:

The java package must match the Ruby module in which your class sits. If your class is in the PgArrayParser module, your class must be in the pgarrayparser (all lowercase).
If you want to instantiate a PgArrayParserEngine class, then you BasicLibraryService must be called PgArrayParserEngineService.
When using @JRubyMethod, specify the name of the method.

I have found Yoko's article on the subject most useful, along with this recent post.

I have applied these different elements to your project here, and I can call the method from IRB -- and the first spec passes!

answered Sep 3, 2012 at 17:58

Sébastien Le Callonnec

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1 Comment

Dan McClain Over a year ago

If you want to submit this as a pull request, I would love to give you full credit for the help!

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