Last updated October 02, 2009 21:59, by Nick Sieger

ActiveRecord JDBC

activerecord-jdbc-adapter is a database adapter for Rails' ActiveRecord component that can be used with JRuby. It allows use of virtually any JDBC-compliant database with your JRuby on Rails application.

Project Info


What's there, and what is not there:

  • MySQL - Complete support
  • PostgreSQL - Complete support
  • Oracle - Complete support
  • Microsoft SQL Server - Complete support except for change_column_default
  • DB2 - Complete, except for the migrations:
    • change_column
    • change_column_default
    • remove_column
    • rename_column
    • add_index
    • remove_index
    • rename_table
  • FireBird - Complete, except for change_column_default and rename_column
  • Derby - Complete, except for:
    • change_column
    • change_column_default
    • remove_column
    • rename_column
  • HSQLDB - Complete
  • H2 - Complete
  • SQLite3 - work in progress
  • Informix - Fairly complete support, all tests pass and migrations appear to work. Comments welcome.

Other databases will require testing and likely a custom configuration module. Please join the mailing lists to help us discover support for more databases.

Using ActiveRecord JDBC

Inside Rails

To use activerecord-jdbc-adapter with JRuby on Rails:

1. Choose the adapter you wish to gem install. The following pre-packaged adapters are available:

  • base jdbc (activerecord-jdbc-adapter). Supports all available databases via JDBC, but requires you to download and manually install the database vendor's JDBC driver .jar file.
  • mysql (activerecord-jdbcmysql-adapter)
  • postgresql (activerecord-jdbcpostgresql-adapter)
  • derby (activerecord-jdbcderby-adapter)
  • hsqldb (activerecord-jdbchsqldb-adapter)
  • h2 (activerecord-jdbch2-adapter)

2. Run the "jdbc" generator to prepare your Rails application for JDBC.

    jruby script/generate jdbc

The initializer and rake task files generated are guarded such that they won't be loaded if you still run your application un C Ruby.

Legacy: If you're using Rails prior to version 2.0, you'll need to add one-time setup to your config/environment.rb file in your Rails application. Add the following lines just before the Rails::Initializer. (If you're using activerecord-jdbc-adapter under the old gem name used in versions 0.5 and earlier (ActiveRecord-JDBC), replace 'activerecord-jdbc-adapter' with 'ActiveRecord-JDBC' below.)

    if RUBY_PLATFORM =~ /java/
      require 'rubygems'
      gem 'activerecord-jdbc-adapter'
      require 'jdbc_adapter'

3. Configure your database.yml in the normal Rails style.

Legacy configuration: If you use one of the convenience 'activerecord-jdbcXXX-adapter' adapters, you can still put a 'jdbc' prefix in front of the databas adapter name as below.

      adapter: jdbcmysql
      username: blog
      hostname: localhost
      database: weblog_development

For other databases, you'll need to know the database driver class and URL. Example:

      adapter: jdbc
      username: blog
      driver: com.mysql.jdbc.Driver
      url: jdbc:mysql://localhost:3306/weblog_development

Standalone, with ActiveRecord

1. Install the gem with JRuby:

    jruby -S gem install activerecord-jdbc-adapter

If you wish to use the adapter for a specific database, you can install it directly and a driver gem will be installed as well:

    jruby -S gem install activerecord-jdbcderby-adapter

2. If using ActiveRecord 2.0 (Rails 2.0) or greater, you can skip to the next step. Otherwise, ensure the following code gets executed in your script:

    require 'rubygems'
    gem 'activerecord-jdbc-adapter'
    require 'jdbc_adapter'
    require 'active_record'

3. After this you can establish a JDBC connection like this:

      :adapter => 'jdbcderby',
      :database => "db/my-database"

or like this (but requires that you manually put the driver jar on the classpath):

      :adapter => 'jdbc',
      :driver => 'org.apache.derby.jdbc.EmbeddedDriver',
      :url => 'jdbc:derby:test_ar;create=true'

Getting the source

The source for activerecord-jdbc-adapter is available using git.

  git clone git://

Running AR-JDBC's Tests

Drivers for 6 open-source databases are included. Provided you have MySQL installed, you can simply type jruby -S rake to run the tests. A database named weblog_development is needed beforehand with a connection user of "blog" and an empty password.

If you also have PostgreSQL available, those tests will be run if the `psql' executable can be found. Also ensure you have a database named weblog_development and a user named "blog" and an empty password.

If you want rails logging enabled during these test runs you can edit test/jdbc_common.rb and add the following line:

require 'db/logger'

Running AR Tests

To run the current AR-JDBC sources with ActiveRecord, just use the included "rails:test" task. Be sure to specify a driver and a path to the ActiveRecord sources.

  jruby -S rake rails:test DRIVER=mysql RAILS=/path/activerecord_source_dir


This project was written by Nick Sieger <> and Ola Bini <> with lots of help from the JRuby community.


activerecord-jdbc-adapter is released under a BSD license. See the LICENSE file included with the distribution for details.

Open-source driver gems for activerecord-jdbc-adapter are licensed under the same license the database's drivers are licensed. See each driver gem's LICENSE.txt file for details.

  • Mysql
  • Glassfish
  • Jruby
  • Rails
  • Nblogo
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