Posts tagged with ObjectBuilder

Extensibility through Unity

This is the third part (see part I & part II) of my series on Unity & ObjectBuilder. The previous introductory material was only there to make the stuff described below more accessible and the framework described here is in fact a complete addition to the Unity toolset, it allows you:

• to use Unity much like the Microsoft Extensibility Framework (MEF), i.e. use import/export attributes to combine instances
• to use Unity to create action flows (workflows in fact but the term has an unintended technical conotation here)
• to use Unity to inject at runtime other objects and sub-objects through a dotted attribute notation

Before giving you concrete code samples let me first highlight what I wanted to achieve and why I created this framework in the first place. During the development of GraphSquare (see this article and the architecture series) I needed a flexible mechanism to convert entities and to let the MVC model pass various stages of transformation to serialize things to a variety of export formats (binary, XML, WCF entities and so on). The idea can be best understood as a combination of ORM and serialization. Imagine that you have some domain entities which need to be converted to data entities through a series of actions like depicted in the picture below. Now, the 'transaction' here is a package which combines the start and end result and the 'workflow' is a series of 'actions' which can be chained and which reacts according to what the transaction state (content) is. Obviously, the transformation to an XML output requires a different set of actions than a binary one, yet there is some overlap. Each action requires either the whole domain entity or some part of it and maybe even some information from the already created data entities. In addition, writing code to assign all this to each instance becomes a repetitive task. So, the idea quickly became involved and difficult to implement. Until I realized that Unity and ObjectBuilder together with their extensibility model were perfectly adapted to this kind of paradigm.

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