neo-activerecord-jdbc-adapter

https://github.com/jruby/activerecord-jdbc-adapter

AR-JDBC is a database adapter for Rails' ActiveRecord component designed to be used with JRuby built upon Java's JDBC API for database access. Provides (ActiveRecord) built-in adapters: MySQL, PostgreSQL and SQLite3 as well as adapters for popular databases such as Oracle, SQLServer, DB2, FireBird and even Java (embed) databases: Derby, HSQLDB and H2. It allows to connect to virtually any JDBC-compliant database with your JRuby on Rails application.