Design Patters - more details

Design Patterns in ColdFusion

Content paraphrased from http://www.jroller.com/page/kwiersma.

I keep coming back to these patterns because I support a large application that implements all of them and have been asked to share my knowledge. This is the knowledge! Granted, there is a lot of business logic in the application, but the architecture of the application follows closely the the principles found in these patterns.

Beans ( Business Objects or Value Objects)
DAOs (Data Access Objects)
Gateways (Data Gateway Objects)
Services (Manager Objects)

The Bean

• Typically represents a specific entity in your model

• Carries "encapsulated" data between the different layers of your application

• like a structure, instead of directly accessing data with a key you call a method

• Helps organize data structures instead passing structures around ad-hoc

• Has a consistent and simple interface (Controllable API)

• Has methods called getters/setters (aka accessors) to access data [getFirstName() / setFirstName()]

• Might be composed of other beans

• Easily created with a code generator

DAO (data access object)

• DAOs only interact with one row of data via the primary key

• Used to save/load objects from data storage

• A DAO could interface with: Database / Legacy persistent data storage (XML / Text File)

• Usually have ScRuD method that take a bean

• (ScRuD - Save | (create) | Read | (update) | Delete)

Gateways (Aggregated Data)

• return one or more rows of data

• Typically returns a cfquery object

• Rarely it can return a bean (Querying by User/Pwd)

• Performs functionality that may affect one or more rows

Services: (Kings of the Jungles)

• Contains your business logic:

• Bean Validation / Creation

• Application specific business logic

• Save / Load / Delete from DAO (via the facade pattern)

• Gateway Interaction (via the facade pattern)

• Usually depends on a DAO and Gateway

• Services can consume other services (very social)