The MVC architecture, being the industry standard for networked
applications is employed in the Oracle Applications Framework and various components
of the OA framework help implement the features of MVC.
The Model
The Model in the OA framework is known as the Application
Module or the AM. It is implemented using the Oracle Business
Components for Java (BC4J) which is optimized ready-to-use implementation of
J2EE design patterns. These BC4Js actually help the developers to concentrate
on writing code for business logic rather than code for the connecting glues
and pipes.
The BC4J application model (AM) is basically a container that
manages and provides access to related model objects i.e. the ones that
participate in same end-to-end transactions. Each OA Framework page has a root
AM that is associated with the top level region of the page known as the Page
Layout region.
The other basic functions of the AM are:-
·
Providing context to the
transactions. This context is known as the Page Context.
·
Establishing Database
Connections.
The View
The View in the OA Framework is implemented using the User
Interface XML or UIX. UIX uses XML to describe the components and hierarchy
that make up an application page. The metadata used to describe the UI is
loaded into a database repository, called Meta Data Services (MDS), at
deployment time and optionally at design time as well. UIX also provides runtime
capabilities to translate this metadata into HTML output so that it can be
shown on a Browser or a mobile device. Various features that can be implemented
using OA Framework UI are:-
·
PPR – Partial Page Rendering for displaying only the
requisite parts of a page at a time.
·
Hot
Keys – Numeric keys for easy
access to specific fields on a form
·
LOV
Auto Completion – Also known as List Of
Value Completion that helps search a value to enter from a long list of values
·
Smart
Poplist – Query based independent
drop down lists.
The Control
The Control in the OA Framework is known as the Controller Object
or CO and has a normal java class based implementation. Its major functions
are:-
Handling user-driven
interactions.
Handling application-driven
interactions.
Implementing two step
transactions i.e. two step page flows.
Instantiating the Model
objects.
Invoking appropriate Model
object methods.
Displaying context based UI
messages.
The controller is basically limited to contain two java methods
which are of primary use. One is the processRequest function which is
called when the page is being rendered for the first time. The other function
is the processFormRequest which is called on submits or page events.
Other objects of Concern
The other objects that hold an important place in the OA Framework
are discussed as follows:-
View Objects
A view object is the medium that transports data from the
Application Module i.e. the Model to the UIX based view. The prime purpose of
the view object is to carry the SQL query that will be run by the model. The
flow of view object usage is explained as follows:-
1.
Creating a View Object.
2.
Incorporating the SQL query
in the View Object.
3.
Binding the widgets on the
view or the UI with the View Object Attributes.
4.
AM instantiates the View
Object.
5.
AM executes the view object
query.
6.
Data gets displayed on the
view. (Provided flow point III has been performed correctly).
Entity Objects
View Objects suffice the purpose of display of data from the
underlying database. However, another important task is to perform updates and
inserts on the same data. Entity objects help perform this tedious task. Entity
objects generally bind in one to one format with a database object like a view
or table. The flow of entity object usage is as follows:-
Creating an Entity Object
by choosing the appropriate database object.
Defining a View Object
based on this Entity Object.
Binding the widgets on the
view with the View Object Attributes.
Firing transaction start,
execute and end commands from the CO and the AM.
Executing the required
actions from the View.
