7.2 The need for a representation builder module

7.2.1 Moving the mechanics of representation production out of resource classes

In the core Restlet API, a resource class is responsible for creating the response representation and setting it on the response object. This is done by creating an instance of a subclass of Representation.

For very simple and very complex cases, it makes sense to do this directly in the resource class. In a typical web application, you will often produce representations using a template. In Kauri, this means the resource class should have a handle to (= dependency on) the TemplateService and use that to create a TemplateRepresentation.

This works just fine. However, it is a very 'manual', hardcoded and somewhat laborious way of constructing the representation. It would be easier if the resource class only needs to return a logical representation name and the data objects. The mapping of the logical name to the real implementation can then be done somewhere else, outside of the concern of the resource class. And this is exactly what Kauri's representation module provides.

For people familiar with Spring MVC, this is similar to the ModelAndView and the ViewResolver. For people familiar with Apache Cocoon, this is similar to the sendPage call. For people familiar with JAX-RS, this is somewhat the same role as the MessageBodyWriter providers.