Rjb (Ruby Java Bridge) loader with before_load and after_load hooks

When working with multiple gems or several rails initializer files that use Rjb, you need to make sure that all java dependencies are set up before running Rjb::load. This is necessary because Rjb can only be loaded once.

As an example, you could use rjb-loader to change classpath and java options. You can do this by adding a 'before_load' hook to your gem or rails initializer.

The 'after_load' hook, on the other hand, should be used when your code needs to run after Rjb::load. For instance, when you need to use java classes.

gem install rjb-loader

Add rjb-loader to your Gemfile:

  gem "rjb-loader"

For any issues related to the java/ruby integration, please check out: http://rjb.rubyforge.org/. You will find here plenty tips that might help you to solve your problem.

Example from jasper-rails:

  ...
  
  RjbLoader.before_load do |config|
  
    # This code changes the JVM classpath, so it has to run BEFORE loading Rjb.
    Dir["#{File.dirname(__FILE__)}/java/*.jar"].each do |path|
      config.classpath << File::PATH_SEPARATOR + File.expand_path(path)
    end
    
    # We can also change java options here, if we want to.
    config.java_options += ['-Xms256M', '-Xmx512M']
    
  end
  
  RjbLoader.after_load do |config|
  
    # This code needs java classes, so it has to run AFTER loading Rjb.
    _Locale = Rjb::import 'java.util.Locale'
    JasperRails.config[:report_params]["REPORT_LOCALE"]    = _Locale.new('en', 'US')
    
  end
  ...

Copyright (C) 2013 Marlus Saraiva

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