JRuby include_package doesn't define constants

Using include_package in a module to import java classes in JRuby usually works as expected, but not always. Try this code in JRuby 1.5.3

$ jruby ns.rb

ns.rb:

require 'java'
require 'pp'

class Rule
end

module MyCompany
 module JavaModel
   include_package 'com.model'
 end
end

pp MyCompany::JavaModel.const_get('Foo')
pp MyCompany::JavaModel.const_get('Rule')

You can simple create two java files and compile them using javac.

com/model/Foo.java:

package com.model;
public class Foo {
}

com/model/Rule.java:
package com.model;
public class Rule {
}

$ javac com/model/Foo.java
$ javac com/model/Rule.java

Here is the output:

Java::ComModel::Foo
Rule

Why the second line is not Java::ComModel::Rule? include_package just overrides const_missing instead of defining constants in module MyCompany::JavaModel. When you call MyCompany::JavaModel.const_get("Rule"), the constant "Rule" is defined, const_missing is skipped.

Using java_import will work correctly although you have to list each class.

module MyCompany
  module JavaModel
    java_import 'com.model.Foo'
    java_import 'com.model.Rule'
  end
end

Note: if you use java_import outside the module, you will overwrite the constant Rule.