The Project | About Us | Contribute | Donations | License

HOME

In this section, we will explore the concept of layered architecture, a fundamental design principle in system architecture. Layered architecture helps in organizing code and responsibilities, making systems more maintainable, scalable, and testable.

Key Concepts of Layered Architecture

Separation of Concerns: Each layer in the architecture has a specific responsibility, reducing the complexity of the system.
Modularity: Layers are modular, meaning changes in one layer have minimal impact on others.
Reusability: Components within a layer can be reused across different parts of the application.
Maintainability: Easier to maintain and update the system as each layer can be modified independently.

Common Layers in an Architecture

Presentation Layer: The user interface of the application.
Business Logic Layer: Contains the core functionality and business rules.
Data Access Layer: Manages data retrieval and storage.
Database Layer: The actual database where data is stored.

Example of a Layered Architecture

Let's consider a simple e-commerce application to illustrate the layered architecture.

Presentation Layer:
- Handles user interactions.
- Displays products, manages the shopping cart, and processes orders.
- Technologies: HTML, CSS, JavaScript, React, Angular.
Business Logic Layer:
- Implements business rules like calculating discounts, processing payments, and managing inventory.
- Technologies: Java, C#, Python.
Data Access Layer:
- Interacts with the database to fetch and store data.
- Technologies: JDBC, Entity Framework, Hibernate.
Database Layer:
- Stores the actual data.
- Technologies: MySQL, PostgreSQL, MongoDB.

Example Code Snippet

Below is a simple example in Java demonstrating the interaction between the Business Logic Layer and the Data Access Layer.

// Data Access Layer
public class ProductRepository {
    public Product getProductById(int id) {
        // Simulate database access
        return new Product(id, "Sample Product", 100.0);
    }
}

// Business Logic Layer
public class ProductService {
    private ProductRepository productRepository = new ProductRepository();

    public Product getProductDetails(int id) {
        return productRepository.getProductById(id);
    }
}

// Presentation Layer
public class ProductController {
    private ProductService productService = new ProductService();

    public void displayProduct(int id) {
        Product product = productService.getProductDetails(id);
        System.out.println("Product Name: " + product.getName());
        System.out.println("Product Price: " + product.getPrice());
    }

    public static void main(String[] args) {
        ProductController controller = new ProductController();
        controller.displayProduct(1);
    }
}

// Product Class
class Product {
    private int id;
    private String name;
    private double price;

    public Product(int id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }
}

Explanation

ProductRepository: Represents the Data Access Layer, simulating a database call.
ProductService: Represents the Business Logic Layer, fetching product details using the repository.
ProductController: Represents the Presentation Layer, displaying product details to the user.
Product: A simple model class representing a product.

Practical Exercise

Exercise: Implement a Layered Architecture

Task: Implement a simple library management system with the following layers:

Presentation Layer: Console-based interface for user interactions.
Business Logic Layer: Manage book borrowing and returning.
Data Access Layer: Simulate database operations for books.

Steps:

Create a Book class with attributes like id, title, and author.
Implement a BookRepository class for data access operations.
Implement a LibraryService class for business logic.
Implement a LibraryController class for user interactions.

Solution

// Book Class
class Book {
    private int id;
    private String title;
    private String author;

    public Book(int id, String title, String author) {
        this.id = id;
        this.title = title;
        this.author = author;
    }

    public int getId() {
        return id;
    }

    public String getTitle() {
        return title;
    }

    public String getAuthor() {
        return author;
    }
}

// Data Access Layer
class BookRepository {
    private List<Book> books = new ArrayList<>();

    public BookRepository() {
        books.add(new Book(1, "1984", "George Orwell"));
        books.add(new Book(2, "To Kill a Mockingbird", "Harper Lee"));
    }

    public Book getBookById(int id) {
        return books.stream().filter(book -> book.getId() == id).findFirst().orElse(null);
    }

    public List<Book> getAllBooks() {
        return books;
    }
}

// Business Logic Layer
class LibraryService {
    private BookRepository bookRepository = new BookRepository();

    public Book borrowBook(int id) {
        return bookRepository.getBookById(id);
    }

    public List<Book> listAvailableBooks() {
        return bookRepository.getAllBooks();
    }
}

// Presentation Layer
public class LibraryController {
    private LibraryService libraryService = new LibraryService();

    public void displayAvailableBooks() {
        List<Book> books = libraryService.listAvailableBooks();
        for (Book book : books) {
            System.out.println("ID: " + book.getId() + ", Title: " + book.getTitle() + ", Author: " + book.getAuthor());
        }
    }

    public void borrowBook(int id) {
        Book book = libraryService.borrowBook(id);
        if (book != null) {
            System.out.println("Borrowed Book: " + book.getTitle());
        } else {
            System.out.println("Book not found.");
        }
    }

    public static void main(String[] args) {
        LibraryController controller = new LibraryController();
        controller.displayAvailableBooks();
        controller.borrowBook(1);
    }
}

Common Mistakes and Tips

Mistake: Tight coupling between layers.
- Tip: Use interfaces to decouple layers.
Mistake: Mixing business logic with data access code.
- Tip: Keep business logic and data access code in separate classes.

Conclusion

In this section, we explored the concept of layered architecture, its benefits, and how it can be implemented in a simple application. Understanding and applying layered architecture principles is crucial for building maintainable, scalable, and robust systems. In the next section, we will delve into the differences between microservices and monolithic architectures.

System Architectures: Principles and Practices for Designing Robust and Scalable Technological Architectures

Layers of an Architecture

Key Concepts of Layered Architecture

Common Layers in an Architecture

Example of a Layered Architecture

Example Code Snippet

Explanation

Practical Exercise

Exercise: Implement a Layered Architecture

Solution

Common Mistakes and Tips

Conclusion

System Architectures: Principles and Practices for Designing Robust and Scalable Technological Architectures

Module 1: Introduction to System Architectures

Module 2: Design Principles of Architectures

Module 3: Components of a System Architecture

Module 4: Scalability and Performance

Module 5: Security in System Architectures

Module 6: Tools and Technologies

Module 7: Case Studies and Practical Examples

Module 8: Trends and Future of System Architectures