Мульти-уровневая система: эффективный подход к организации

Multi-level architecture

Multi-level architecture, also known as layered architecture, is a popular approach in software development. It organizes a system into a hierarchy of layers, each of which performs specific functions. This approach allows for the creation of a flexible and modular system, where each level has defined responsibilities and interacts with other levels.

Applying multi-level architecture offers the following advantages:

1. Responsibility separation: Each level of the system is responsible for a specific function, such as business logic, data management, or presentation. This facilitates modification and updates to the system, as changes in one level do not affect other levels.
2. Code reusability: Methods and functionalities implemented at one level can be used by other levels. For example, classes and methods written at the data access level can be reused at the business logic level. This helps reduce code duplication and improve development efficiency.
3. Testability: Each level can be tested separately, making the overall testing process easier. Business logic can be tested using unit tests, the user interface can be tested using functional tests, and the data access level can be tested using integration tests.

Below are some code examples for each level of multi-level architecture:

Presentation level:

public class UserController {
    private UserView userView;
    private UserService userService;

    public UserController() {
        this.userView = new UserView();
        this.userService = new UserService();
    }

    public void displayUser(int userId) {
        try {
            User user = userService.getUser(userId);
            userView.displayUser(user);
        } catch (Exception e) {
            userView.displayError("Failed to display user.");
        }
    }
}

Business logic level:

public class UserService {
    private UserRepository userRepository;

    public UserService() {
        this.userRepository = new UserRepository();
    }

    public User getUser(int userId) {
        // Some business logic
        // For example, retrieving user data from the repository
        return userRepository.getUser(userId);
    }
}

Data access level:

public class UserRepository {
    public User getUser(int userId) {
        // Code for retrieving user data from a database or another source
        // Example:
        Connection connection = DriverManager.getConnection(url, username, password);
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery("SELECT * FROM users WHERE id = " + userId);
        
        if (resultSet.next()) {
            // Creating a user object and populating it with data from the query results
            User user = new User();
            user.setId(resultSet.getInt("id"));
            user.setName(resultSet.getString("name"));
            user.setEmail(resultSet.getString("email"));
            return user;
        } else {
            throw new Exception("User with ID " + userId + " not found.");
        }
    }
}

The above examples showcase code snippets at different levels of multi-level architecture. These examples demonstrate how each level performs its functions and interacts with other levels. This approach helps create more maintainable, scalable, and flexible systems.