Model View Control

Why

Reduce the complexity in architectural design, increase flexibility and maintainability. Write reusable (modular) software.

How

Decouple model from view and control. Put all the plumbing into corresponding super-classes.

Action

For each View create a JSF-page mypage.xhtml and two Java classes ViewMypage.java and ControllerMypage.java.

The JSF-page defines the elements and the layout of the page.

Content is loaded and saved dynamically from the Java class ViewMypage.java. This Bean contains data from the model. Note: No load, save or other model methods are called in this class.

Flow of control request (navigation) and model updates (computations) are channeld through the class ControllerMypage.java. Note: This class contains methods which are called upon entering and leaving the page to ensure consistant data.

Example

Consider a page for retrieving a book. The JSF-page retrieve.xhtml contains elements for entering search information, a button to start the search, and a table to display author, title and keywords of the found books. Each row is a link to a JSF-page, where the contents of the book is displayed.

The Java-class ViewRetrieve.java contains Getters and Setters for the data to be displayed by the elements of the JSF-page retivieve.xhtml. Data is taken from a local database which is maintained (updated) by the model.

The Java-class ControllerRetrieve.java handles the action events and page requests (navigation), i.e. calls model methods to search the books (which update the database used by the View-class) and issues the request to navigate to the new page.