This document discusses the facade design pattern. The facade pattern provides a simplified interface to a more complex subsystem. It decouples the subsystem from the client and makes the subsystem easier to use. A facade acts as a front-facing interface that hides the underlying complexities of the subsystem and delegates client requests to appropriate subsystem classes. This reduces dependencies between subsystems and promotes loose coupling. The facade pattern is useful for layering subsystems and simplifying access to them through a single interface.

1. Design Patterns
Facade Pattern
(A Structural Pattern)
Prsented By:
Jainik Patel(112332)
Darshan Darji(112333)
Dhiraj Rajput(112338)
Prashant Goswami(112344)

2. Facade
A structural design pattern
 Decouples interface from implementation
 Intent
 To provide a unified interface to a set of interfaces in a
subsystem
 To simplify an existing interface
 Defines a higher-level interface that makes the subsystem
easier to use

3. Facade Problem & Solution
Subsystem
classes
Client
classes
FACADE

4. Motivation
• Structuring a system into subsystems helps reduce complexity.
• A common design goal is to minimize the communication and
dependencies between subsystems.
• One way to achieve this goal is to introduce a facade object that
provides a single, simplified interface to the more general
facilities of a subsystem.

5. Applicability
Use the Facade pattern when
Facade to decouple the subsystem for clients and other
subsystems
To layer your subsystem. Use facade to define an entry point to
each subsystem level. If subsystems are dependent, then you
can simplify the dependencies between them by making them
communicate with each other through their facades.

6. Facade Structure

7. Participants
Facade
knows which subsystem classes are responsible for a
request.
delegates client requests to appropriate subsystem objects.
subsystem classes
implement subsystem functionality.
handle work assigned by the Facade object.

8. Collaborations
Clients communicate with the subsystem by sending
requests to Facade, which forwards them to the appropriate
subsystem object(s). Although the subsystem objects
perform the actual work, the facade may have to do work of
its own to translate its interface to subsystem interfaces.

9. Consequences
The Facade pattern offers the following benefits:
It shields clients from subsystem components, thereby
reducing the number of objects that clients deal with and
making the subsystem easier to use.
It promotes weak coupling between the subsystem and its
clients.
Help in layering the systems helps elements circular
dependency.

10. Implementation
 Sub System easier to use
 Strongly Coupled.
 We're going to create a MobileShope interface and concrete
classes implementing the MobileShope interface. A facade class
ShopeKeeperFacade is defined as a next step.
 ShopeKeeperFacade class uses the concrete classes to delegates
user calls to these classes FacadeClient, our Client class will use
ShopeKeeperFacade class to show the results.

11. Example Class Diagram

12. Example Class Diagram

13. Facade Pattern
 Related Pattern
 Abstract Factory Pattern
 Common Variations
 Key: Don’t add new behavior, just simplify interface to existing
behavior
 Java API Usage
 java.net.URL
 client can use it without being aware of classes that allow it to
work
 client can use classes like URLConnection directly if they
choose

14. THANK YOU