README.md

💳 Payment Processing System (Spring Framework)

A simple and extensible Payment Processing System built using the Spring Framework (Core + Dependency Injection). This project demonstrates how to use Factory Design Pattern + Spring’s Dependency Injection to dynamically select and process different payment methods.

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🚀 Features

• Supports multiple payment types:

  • UPI
  • Credit Card
  • Debit Card

• Uses Spring Annotation-based Configuration

• Implements Factory Design Pattern

• Easily extendable for new payment methods

• Clean and modular architecture

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🧠 Concept Used

• Spring IoC Container
• Dependency Injection (DI)
• Component Scanning
• Factory Design Pattern
• Interface-based programming

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📁 Project Structure

com.nit
│
├── config
│   └── AppConfig.java
│
├── main
│   └── TestApp.java
│
└── sbeans
    ├── Payment.java
    ├── PaymentFactory.java
    ├── CreditCardPayment.java
    ├── DebitCardPayment.java
    └── UPIPayment.java

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⚙️ Configuration

AppConfig.java

Spring configuration class with component scanning:

@Configuration
@ComponentScan(basePackages="com.nit.sbeans")
public class AppConfig {
}

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🧩 Core Components

1. Payment Interface

public interface Payment {
    String pay(double amount);
}

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2. Payment Implementations

💳 Credit Card

@Component("credit")
public class CreditCardPayment implements Payment {
    public String pay(double amount) {
        double discount = 10;
        double finalAmount = amount - (amount * discount);
        return "Paid " + finalAmount + " using Credit Card";
    }
}

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💳 Debit Card

@Component("debit")
public class DebitCardPayment implements Payment {
    public String pay(double amount) {
        double discount = 5;
        double finalAmount = amount - (amount * discount);
        return "Paid " + finalAmount + " using Debit Card";
    }
}

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📱 UPI

@Component("upi")
public class UPIPayment implements Payment {
    public String pay(double amount) {
        double discount = 15;
        double finalAmount = amount - (amount * discount);
        return "Paid " + finalAmount + " using UPI";
    }
}

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3. Payment Factory

Handles dynamic selection of payment method using Spring's auto-wired map:

@Component
public class PaymentFactory {

    @Autowired
    private Map<String, Payment> paymentMap;

    public Payment getPayment(String type) {
        Payment payment = paymentMap.get(type.toLowerCase());

        if (payment == null) {
            throw new IllegalArgumentException("Invalid Payment Type");
        }
        return payment;
    }
}

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▶️ Running the Application

TestApp.java

public class TestApp {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx =
            new AnnotationConfigApplicationContext(AppConfig.class);

        PaymentFactory paymentFactory = ctx.getBean(PaymentFactory.class);

        try {
            Payment payment = paymentFactory.getPayment("upi");
            System.out.println(payment.pay(50000));
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

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💡 Example Output

Paid -700000.0 using UPI

(Note: Discount calculation currently multiplies instead of percentage — can be improved)

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🛠️ How It Works

1. Spring scans all @Component classes.
2. Each payment method is registered with a unique name (credit, debit, upi).
3. Spring injects all implementations into a Map<String, Payment>.
4. PaymentFactory selects the correct implementation dynamically.
5. TestApp triggers the payment process.

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🔥 Future Improvements

• Fix discount calculation logic (use percentage properly)
• Add new payment methods (Net Banking, Wallets)
• Add logging (SLF4J / Log4j)
• Add REST API layer (Spring Boot)
• Add unit testing (JUnit)

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📌 Key Takeaway

This project shows how Spring + Factory Pattern can eliminate complex if-else or switch statements and make the system clean, scalable, and maintainable.

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🧑‍💻 Author

Built as a learning project for understanding Spring Core concepts and design patterns.

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⭐ If you found this useful

Give it a ⭐ on GitHub and keep building 🚀