Java::Override JRuby Module

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Java::Override is a JRuby module that enables overriding native Java methods with Ruby naming conventions. JRuby allows you to call Java methods (members of native Java classes/interfaces) with Ruby naming style. Therefore you can use snake_case and Ruby-like accessors instead of JavaBean ones.

In JRuby JavaBean accessors are translated to their Ruby counterparts (e.g. getFooBar can be accessed via foo_bar, isFooBar via foo_bar?, or setFooBar via foo_bar=). Those methods are added to Java classes as JRuby aliases. However, if we want to override a Java method we cannot define a Ruby-like method because JVM won't see it. JVM performs polymorphic calls on its own, native methods. And so we have to override native Java methods and it doesn't look much pretty in JRuby code.

But the Java::Override module abolishes this inconvenience. Once included in the subclass it creates aliases to native Java methods and supports inheritance and polymorphism that way. Moreover, it adds proper aliases for Java interfaces included as modules.

Here is a good looking simple implementation of javax.swing.table.AbstractTableModel class.

require 'java/override'

java_import javax::swing::table::AbstractTableModel

class MyTableModel < AbstractTableModel
  include Java::Override

  def initialize
    super
    @column_names = ['First Name', 'Last Name']
    @data = [
      ['John', 'Doe'],
      ['Jack', 'FooBar']
    ]
  end

  def column_count
    @column_names.size
  end

  def row_count
    @data.size
  end

  def column_name(col)
    @column_names[col]
  end

  def get_value_at(row, col)
    @data[row][col]
  end

  def column_class(col)
    get_value_at(0, c).java_class
  end

  def cell_editable?(row, col)
    col.zero?
  end

  def set_value_at(value, row, col)
    @data[row][col] = value
    fire_table_cell_updated(row, col)
  end
end

Java::Override requires JRuby in 1.9 mode and a decent JVM. It has been tested under JRuby 1.6.2 and Oracle Java 7 JDK.

$ gem install java_override

Copyright (c) 2012 Szymon Wrozynski

See LICENSE.txt for details.