Java and Model View Control MVC

1
Java and Model View Control -MVC-

• Vangelis Mavridis
• COMM3C Java Network Programming
• 11 June 2003

2
Introduction to the MVC

• Model/View/Controller is a general pattern that
  is being used for designing user interfaces.
• MVC was first introduced as part of the Smalltalk
  programming language.
• Its implementation in Java can be found in the
  Swing user interface components that are included
  in the Java Foundation Classes (JFC).

3
Introduction to the MVC 2

• Other implementations of MVC can be found in
• CAD systems, where design can be viewed from
  different perspectives.
• Charts such as pie-charts, bar-charts or line
  charts that share common data.

4
MVC architecture

• According to the MVC architecture, all software
  modules are separated into three distinct pieces
  a model, a view, and a controller.

Model
View
Controller
5
MVC architecture 2

• The model piece is responsible for the state and
  the behaviour of the module. Here, all changes on
  the state are monitored and executed.
• The view piece is responsible for the
  visualisation of the state from the model.
  Multiple views can be applied to a model.
• The controller piece manages the interaction from
  the user with the model. Through the controller,
  changes can be made to the state of the model.

6
Benefits of MVC

• Flexibility and reuseability.
• The dynamic relationship between the model and
  view pieces that allows for changes occurring at
  run-time rather than during compilation.
• The separation of a program into modules allows
  for problems to be faced easier.

7
Benefits of MVC 2

• Designing parts of the program separately at
  run-time can help manageability and future
  modifications.
• Future modifications can be made easier by
  changing only segments of the program.

8
MVC and Java Swing

• MVC is implemented in Java in the Swing UI
  components of the JFC classes.

Model
View
Controller
9
MVC and Java Swing 2

• Java swing uses a different view of the MVC
  pattern. Here, the model piece remains individual
  while the view and controller pieces are combined
  into one component.
• All the components in Java Swing have already
  defined data models. These can be either built-in
  classes or user defined classes.

10
The benefits of MVC in Java

• Implementing the MVC pattern in Java results to
  the creation of a higly flexible user interface
  toolkit.
• Therefore, Swings components such as buttons,
  tables or scrollbars can be modified
  simultaneously while they are being used.

11
An example of use

• How MVC is applied in the Java Swing set can be
  shown by examining the button component.
• The ButtonModel interface shows the behaviour of
  the model in the button component. Here the
  instance of the button is created by the model.
  Also, through the model the button behaviour is
  defined.
• The same interface also uses methods aimed at
  questioning or altering the internal state of the
  button, adding and removing event listeners or
  initiating events.

12
An example of use 2

• The ButtonUI interface shows how the view and
  controller act in the button component. When this
  interface is used by classes, code can be written
  for creating the visual appearance of a button as
  well as handling input coming from the keyboard
  or the mouse.
• Some of the methods used by the interface are
  the Paint method, the handling of AWT events or
  the handling of geometric information.