eXpressApp Framework 之DC技術入門系列(1)

好久沒有寫部落格了,一個是工作忙的原因,二一個就是自己這兩年的生活方面發生了太多的事情,導致自己沒有精力寫,最近,隨著Devexpress公司的ORM架構工具XAF v20011.1的即將發布,隨XAF的一個新的技術----DomainComponent(下文簡稱DC)也將正式發布.

以前我們用XAF開發實體物件的時候,用的最多的就是Domain Object(下文簡稱DO),但是,我們在使用的過程中會發現,DO有明顯的局限性,比如在拓展複用方面就很是不盡如人意,特別是DO不能脫離XAF運行,這給我們的實際開發帶來了成本方面的困擾,而DC在這方面就做了非常大膽的嘗試,下面我們來瞭解下DC技術.

在這系列文章中,我將全部盡量使用DC技術進行介紹其使用方面的入門知識,並將會以一個簡單採購系統作為介紹切入點,用執行個體讓大家感受下DC能給我帶來怎樣的震撼

注:更多的詳細資料,大家可以訪問Devexpress 的官方網站http://www.devexpress.com/去瞭解,官網可以下載到xaf的30天試用版本,聲明:提供此資訊只是為了方便感興趣的同行,僅此而已.

本次我們先來瞭解什麼是DC?看看官方是怎麼定義的:

Domain Components technology is designed to simplify data management and
reusability by providing a much more flexible and abstracted approach to
business object design. You can compose an application from reusable blocks,
abstracted away from a particular persistence layer.

With Domain Components you define interfaces instead of regular business
objects inherited from XPO classes. These interfaces will declare required
properties or data fields. The way this data is to be processed ( Domain Logic)
is then defined by creating special classes that determine how interface members
behave when an object is constructed, when properties are changed, etc. Actual
business classes are automatically implemented by XAF at runtime based on the
provided logic and interfaces. You can package interfaces and domain logic in an
assembly, and use it as a domain library. If you then create a new XAF
application, you can reference the domain library and reuse domain components.
Since interfaces support multiple inheritance, required business objects can be
combined into new domain components. With interfaces you can make your domain
model independent of implementation.

Benefits of the Domain Components Technology

Domain Components Technology is not by any means a replacement for the
regular business classes approach for defining
domain entities. The main advantage of the technology is the ability to create
reusable domain libraries containing components that can be combined in any way.
If you do not need the ability to create reusable components and combine them,
most probably you will not need to use Domain Components. The following list
describes the benefits of the Domain Components technology and should help you
decide whether or not the approach is right for your task.

• You can create reusable domain libraries.

  Most likely, each new XAF application you develop is not unique. The most
  common objects, such as Person, Phone, Address, etc., are always used. The Business Class Library provides you with
  a set of classes that you will need most frequently. But implementing your own
  reusable library is not a simple task. With Domain Components you can easily
  package an assembly and reference it in your applications.

• You can use multiple inheritance.

  Since Domain Components are represented by interfaces and not by classes, you
  can use multiple inheritance to combine several previously defined components
  into a new one. The new Domain Component will expose the properties of all its
  ancestors and utilize their Domain Logic. Of course you can add new properties
  and apply additional logic.

• You do not need to inherit from Base Persistent Classes when implementing
  Domain Components.

  Each regular business class is derived from one of the Base Persistent Classes in XAF. The
  behavior of these classes differs. For instance, a base class can either expose
  an auto-generated primary key property of an integer or Guid type, or not. The
  choice of the base class is made once a class is implemented. With Domain
  Components, you can use a specific base class in each new scenario (see the ITypesInfo.AddEntityToGenerate
  method overload that takes the baseClass parameter). However, attributes
  applicable to regular business classes and their properties can also be used
  with Domain Components. And of course, an object implemented via Domain
  Components does not differ from an object implemented in a standard way from the
  end-user or application administrator point of view.