Facade Pattern

Overview

The Facade Pattern is a structural design pattern that provides a simplified interface to a complex subsystem. It acts as a bridge between the client and the complex system, making it easier to interact with.

Definition

A Facade is an object that provides a simple interface to a larger body of code, such as a class library or a set of classes.

Key takeaways:

• Encapsulates complex subsystems.
• Defines a higher-level interface that makes the subsystem easier to use.
• Reduces dependencies between the client code and the subsystems.

Structure

class Facade {
    private Subsystem1 subsystem1;
    private Subsystem2 subsystem2;

    public Facade() {
        this.subsystem1 = new Subsystem1();
        this.subsystem2 = new Subsystem2();
    }

    public void simplifiedMethod() {
        subsystem1.operation1();
        subsystem2.operation2();
    }
}

class Subsystem1 {
    public void operation1() {
        // Complex logic
    }
}

class Subsystem2 {
    public void operation2() {
        // More complex logic
    }
}
            

Implementation

Here’s a step-by-step implementation example:

1. Create complex subsystems.
2. Define the Facade class that interacts with these subsystems.
3. Expose simple methods in the Facade class to the client.
4. Use the Facade in client code to interact with the subsystems.

class Client {
    public static void main(String[] args) {
        Facade facade = new Facade();
        facade.simplifiedMethod(); // Easy interaction with complex subsystems
    }
}
                

Best Practices

Consider the following best practices when implementing the Facade Pattern:

• Use the Facade Pattern when working with complex systems.
• Keep the Facade class stable while allowing subsystems to evolve.
• Don’t overload the Facade with too many responsibilities.

FAQ