Façade Pattern

Tags
Design Pattern, Java

Introduction

• Purpose
  • Supplies a single interface to a set of interfaces within a system.
• Use When
  • A simple interface is needed to provide access to a complex system.
  • There are many dependencies between system implementations and clients.
  • Systems and subsystems should be layered.
• Characteristics
  • Provide a unified interface to a set of interfaces in a subsystem. It defines a higher-level interface that makes a subsystem easier to use.
  • Does not prevent sophisticated clients from accessing the underlying classes.
  • It doesn’t add any functionality. It just simplifies interfaces.
• Benefits
  • Hides the implementations of the subsystem from clients.
    • makes the subsystem easier to use
  • Promotes weak coupling between the subsystem and its clients
    • allows changing the classes comprising the subsystem without affecting the clients

How to Use (Example)

• A set of interfaces

  public class Class1 {
      public void doSomething() {
          System.out.print("Hello, ");
      }
  }
  public class Class2 {
      public void doSomething() {
          System.out.print("World!");
      }
  }
  

• Façade

  public class MyClass {
      public void doSomething() {
          Class1 c1 = new Class1();
          Class2 c2 = new Class2();
          c1.doSomething();
          c2.doSomething();
      }
  }