====== Commerce Facades - Key Concepts and Features =====
The **commercefacades** extension exposes a group of facades which simplify the communication between the store frontend and the service layer. This is a summary which I wrote while studying for the certification. The Hybris Documentation about commercefacades has one page and it is worth reading.

===== Key Concepts ======

  * The facades return **data objects** which are completely separated from the models. They can be extend using the file ***-beans.xml.**
  * Each method fulfills a **business action.**
  * The **conversion between models and data objects** is done by the converters and populators.
    * A **converter** may create the target object and contains a list of populators.
    * A **populator** fills in some fields (or calculates using services) of the data object to be used in the front-end.
    * Populators must be independent and must have a clear goal, so they can be easily reused.
    * Both are injected using Spring. The new constructor must be avoid.
    * Data objects are instanced using a Spring bean with the prototype scope which is defined in **beans.xml**.
    * All the converters are an instance of AbstractConverter or **AbstractPopulatingConverter**
    * **ConfigurablePopulators** may implement different conversion rules based on a set of enums.
      * First the converter creates a data object using all the populators which fill the mandatory fields.
      * Then a configurable populator fills the fields which are only required by some components/pages of the front-end. It has a Map<Enum option, populator>.
    * [[https://help.sap.com/viewer/9d346683b0084da2938be8a285c0c27a/6.5.0.0/en-US/8b937ff886691014815fcd31ff1de47a.html|A class diagram can be found here]]
===== Key Features ======

  * There are facades for:
    * Cart
    * Order
    * Checkout
    * Product (including reviews)
    * Search
    * StoreSession (languages and currencies)
    * User
    * StoreLocator
  * The extension can be **easily extended**.
    * Adding facades
    * New implementation of a facade interface (replacing or adding methods)
    * New converters or populators
    * Adding or replacing populators
    * Extending or new data objects
    * yacceleratorfacades is an example of an extension which extends the facades.
  * Out-of-the-box converters and populators: [[https://help.sap.com/viewer/9d346683b0084da2938be8a285c0c27a/6.5.0.0/en-US/8b832e6286691014a050d0863227d73b.html|commercefacades Extension - Technical Guide]]
  * The **URLResolver** must be implemented to provide relative URLs for the business objects. Hybris comes with URL resolvers for products, categories and search using facets.

===== Workflow ======

The interaction of the controllers, facades, services, DAOs, models and data objects is explained in the this diagram: [[https://wiki.hybris.com/download/attachments/289441083/Simple%20Request%20Interaction%20Diagram.jpg?version=1&amp;modificationDate=1444256224000&amp;api=v|Simple Request Interaction Diagram.jpg]]

**In the B2C Accelerator the converters and the populators are never used to convert from a DTO to a model.** But they could be used.

--Based on Hybris 6.3