Factory

tags: Design Patterns, Creational Design Patterns

What is the Factory Pattern?

• The Factory Pattern is a creational design pattern that provides an interface for creating objects but lets subclasses decide which class to instantiate.
• The Factory pattern creates objects without exposing the creation logic. There will be a common interface through which the newly created object is referenced - Polymorphism.

When to use it?

• When the exact type of object isn’t known until runtime.
• When you want to hide the object creation logic.
• When you have many subclasses of a class or interface

What are the advantages?

• Promotes loose coupling between client and product classes
• Helps in managing complex object creation logic
• Common in frameworks where object creation can vary (like Spring Beans)

Example

Step 1: Define an Interface

public interface Notification {
    void notifyUser();
}

Step 2: Implement Concrete Classes

public class EmailNotification implements Notification {
    @Override
    public void notifyUser() {
        System.out.println("Sending Email Notification");
    }
}
 
public class SMSNotification implements Notification {
    @Override
    public void notifyUser() {
        System.out.println("Sending SMS Notification");
    }
}

Step 3: Create the Factory Class

public class NotificationFactory {
    public static Notification createNotification(String type) {
        if ("EMAIL".equalsIgnoreCase(type)) {
            return new EmailNotification();
        } else if ("SMS".equalsIgnoreCase(type)) {
            return new SMSNotification();
        }
        throw new IllegalArgumentException("Unknown notification type");
    }
}

Step 4: Use the centralized factory method for object creation instead of new keyword.

@RestController
public class NotificationController {
 
    @GetMapping("/notify")
    public String sendNotification(@RequestParam String type) {
        Notification notification = NotificationFactory.createNotification(type);
        notification.notifyUser();
        return "Notification sent!";
    }
}