my first rails plugin: acts_as_roxml

NOTE: Updated on 01-07-08 with Rails 2.0.2 info

In order for our little BPM to function we need to be able to marshal and unmarshal XML quickly and easily. I spent the day researching and coding a solution to this problem.

Rails Active Record models come baked in with fairly flexible to_xml and (as of 2.0) from_xml methods that allows you to serialize/deserialize model objects into transportable and editable xml documents. Unfortunately, the to_xml method (unlike to_json) does not support n-depth serialization. For example, you cannot serialize something like:

• Books
  
  • Philosophy
    
    • Plato: Parmenides
    • Nietzche: Beyond Good & Evil
    
    
  • Fiction
    • Eliot: Middlemarch
    • Tolstoy: War and Peace
    
    
  
  

to_xml only allows the serialization of 1st and 2nd level, the individual books would be left out of the document. Additionally, I am not pleased with the method approach, I want to be able to add new attributes to my xml without having to change each instance of to_xml/from_xml. I also wanted more control over how my XML is structured.

The ROXML approach is closer to what I had in mind. I wanted the power and simplicity of ROXML baked right into my model objects. Simply including ROXML was not an option since it overrides the Active Record accessors. So I grabbed the ROXML source, made a few modifications and came up with acts_as_roxml.


acts_as_roxml allows you to add the annotations described here while providing a couple additional callbacks and helper functions that make it easy to make the following transformations: DB -> Object -> XML -> Object -> DB

The source can be found in our svn server under rails_sandbox/acts_as_roxml. To see it in action run: ruby test/unit/acts_as_roxml_test.rb I'll continue to tweak this while building the process engine. We may wind up with an extra plugin to contribute to the community.

Today:

• Built acts_as_roxml plugin