At my company, we are currently developing an open source package called Ruby on Spring that integrates the JRuby dynamic language with the Spring application framework. Ruby on Spring is open source and licensed under the MIT license

The goals of the project are to permit rapid innovation and iteration, full reuse of our existing Spring and Hibernate business logic and objects, and a smooth transition from prototype to production code.

We were inspired by many of the benefits and philosophy of Ruby on Rails, including avoiding configuration files and compilation. Make a change, and you’ll see it immediately. At the same time, if you’re already commited to Spring, the package doesn’t require you to learn a new framework or abandon your existing investment in Spring. The total size of the package is less than a 1000 lines, so it’s small and easily integrated into existing projects.

The key part of the system is a Spring controller that instantiates a JRuby script engine and executes a JRuby script to define the controller and the model. The view is provided by a standard JSP file. If the JRuby controller is replaced by a Java one, the view can be used as-is with no changes.

Download

You can download a zip file include the source code, a precompiled JAR, and installation instructions from rubyonspring.zip. We have tested the JAR against stock distributions of Spring, Hibernate, and Tomcat; a list of required libraries is included in the installation instructions.

Tutorial

Hello World

The simplest possible example consists of a JRuby script “hello.rb” which returns a model object and a JSP view “hello.jsp” which uses that model. To try the example, I just need to drop these two files into the “rad” directory on my Tomcat server. No compilation, configuration files, or server restarts are required.

Notice that rather than defining an explicit controller class, the script simply returns a model object. This is a shortcut for rapid prototyping. Equivilantly, we could have explicitly defined a controller object as follows:

Reusing Spring Beans

Here’s a more interesting example that reuses business logic from a Spring bean implemented in Java. ($context represents the Spring application context.) Thanks to the magic of JRuby, we can interact and create Java objects just as easily as Ruby ones.

Hibernate Queries

The package also supports Hibernate. The follow example uses Hibernate to fetch a list of company objects starting with a given letter. Note that the query returns full fledged Java objects with behavior, not just data.

The corresponding JSP view uses standard Spring conventions and could be used without changes with a Java controller.

onSubmit Handlers

Our final example is a simple calculator controller. It implements an onSubmit handler to run business logic (computing the calculation) when the user submits the form and choose a new result view.

What’s next

There are a number of items still to be completed, but already the framework has proven useful for several rapid prototyping projects that subsequently became product features.

We need to fully support the <spring :bind> tag or something like it. We’d like to define additional helpers to simplify Hibernate queries, in the style of Rail. More complete documentation and locked down interfaces are on the roadmap.

If you have any issues, or are interested in collaborating, please contact me or Laurel Fan.