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The layers also conform to the MVC pattern in which a controller determines the model and returns the view to render the model.
User Interface Layer
The user interface layer defines different views for displaying the model that is provided by its controller. Such a view may be an edit view for editing an element in the Editor or a website view for rendering the element on the website. The views are created and maintained by the controller. In Spring MVC, such a view can be a JSTL view (JSP), redirect view, download view, or any other view since views are agnostic in Spring MVC.
Web Layer
The web layer is responsible for all communication between the model and the view. It retrieves the HTTP requests, generates the view and returns the result. The controller uses a data transfer object, called the FormBackingObject, to hold the data that must be rendered by the view or to hold data submitted from an HTML form by an end user. The controller handles the transfer of property values between the FormBackingObject and the business objects it represents. The FormBackingObject is closely related to one or more business objects in the domain model layer but is not necessarily the same. For the Editor, the controller is a Spring MVC controller - for the Website this is the ControllerServlet.
The controller is the spider in the web; it is responsible for handling all requests and returning the proper results. The Web layer typically has dependencies with all other layers.
Services Layer
The services layer exposes several services to software components like authorization, configuration, preferences, session management and transaction management. Services provide business logic that involves multiple business objects. Business objects themselves usually only contain logic to update or retrieve its own properties.
Persistence Layer
The persistence layer is responsible for persisting the business objects invoked by the controller. It is good practice to define a DAO in order to prevent the business object from containing dependencies with a particular persistence implementation like the JCR or JDBC calls.
Domain Model Layer
The domain model layer contains all business logic, business objects and business rules. The domain model objects are implemented as POJOs and do not contain references to any of the other layers. The several other layers however may refer to objects in the domain model layer. The business objects usually contain only business logic to update and retrieve their own properties. When business logic involves multiple business objects, it is recommended that you use a service instead.
Abstraction Layers in a Plugin
To identify the several abstraction layers clearly in a plugin, the following guidelines should be followed:
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Generally speaking, the level of stability is measured by methodically, i.e. systematically, running the software during a specified duration, preferably through the means of a balanced set of representative test cases and then registering the number of defects and/or the mean time in-between the occurrences of defects. An indication for the stability is the Mean Time Between Failures (MTBF), the average interval in-between defects that occur during one or more measurement sessions.
Compatibility Guidelines
Software and Hardware Compatibility
For each XperienCentral release, the Hard and Software Requirements is updated which describes the hardware and software on which XperienCentral is supported. The plugin should be compliant with these requirements [G154].
XHTML Compliance
The HTML generated by the JSPs for rendering the plugin in the Editor must be XHTML 1.0 transitional compliant [G042]. HTML generated by the JSPs for rendering the website environment should be XHTML 1.0 transitional compliant [G134].
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