Abstract Factory Pattern

Sep 2, 2019 · 258 words · 2 minute read

The Abstract Factory Pattern adds another layer of abstraction over the Factory Pattern. It has an Abstract Factory Interface which is implemented by several Factory classes. A Super Factory decides which Factory should be used based on the requirement. Abstract Factory Pattern is one the creational design patterns.

Participants 🔗

AbstractFactory An interface which for creating AbstractProduct objects. ConcreteFactory Implements AbstractFactory and creates ConcreteProduct objects. AbstractProduct An interface for type of products. ConcreteProduct Implements AbstractProduct object. Here is where the actual product code is defined. Client Uses methods provided by AbstractFactory and AbstractProduct interfaces to create objects.

UML Diagram 🔗

UML of Abstract Factory Pattern

As you can see in the diagram, There is an AbstractFactory interface which is implemented by 2 factory classes. Client doesn’t access the concrete factory classes directly, instead uses the methods provided by AbstractFactory interface.

Example 🔗

abstract class Computer {
    public abstract void powerOn();
}

class PC extends Computer {

    public void powerOn() {
        System.out.print("Powering on PC...");
    }
}

class Server extends Computer {

    public void powerOn() {
        System.out.print("Powering on server...");
    }
}

interface AbstractComputerFactory {
    Computer createComputer();
}

class PCFactory implements AbstractComputerFactory {

    public Computer createComputer() {
        return new PC();
    }
}

class ServerFactory implements AbstractComputerFactory {

    public Computer createComputer() {
        return new Server();
    }
}

class ComputerFactory {
    public static Computer createComputer(String type) {
        AbstractComputerFactory factory;
        switch (type) {
            case "pc" : factory = new PCFactory(); break;
            case "server" : factory = new ServerFactory(); break;
            default: throw new IllegalArgumentException();
        }

        return factory.createComputer();
    }
}

class Main {
    public static void main(String[] args) {
        ComputerFactory.createComputer("pc").powerOn();
        ComputerFactory.createComputer("server").powerOn();
    }
}

Design Pattern