Creating a Database-Backed Rails Application

1. Go to the <JRUBY_HOME>/samples directory of your JRuby 1.1.4 installation.

2. Create the books application template so that it is configured to use the MySQL database:

   jruby -S rails books -d mysql

3. Go to the books directory you just created.

4. Open the config/database.yml file in a text editor.

5. When prompted, enter your MySQL root password under the development heading in the database.yml file.

6. Go back to the books directory if you are not already there.

7. Create the database by running the following command:

   jruby -S rake db:create

   After the database creation is complete, you should see output similar to the following:

   ** Execute db:create

   The rake command invokes the Rake tool. The Rake tool builds applications by running Rake files, which are written in Ruby and provide instructions for building applications.

8. Create the scaffold and the Book model for the application:

   jruby script/generate scaffold book title:string 
   author:string isbn:string description:text

   When you run the script/generate command you specify the name of the model, the names of the columns, and the types for the data contained in the columns.

   A scaffold is the set of code that Rails generates to handle database operations for a model object, which is Book in this case. The scaffold consists of a controller and some views that allow users to perform the basic operations on a database, such as viewing the data, adding new records, and editing records. Rails also creates the model object when generating the scaffold.

9. Create the database tables:

   jruby -S rake db:migrate

   When Rails is finished creating the tables, you should see output similar to the following:

   CreateBooks: migrated (0.1322ms) =========

   If you need to reset the database later, you can run jruby —S rake db:reset.