Neuda project is a Spring Boot-based banking system designed with a modular structure, ensuring maintainability and separation of concerns. It follows standard practices by organizing components into packages for models, repositories, services, controllers, and exceptions. The Account and Transaction entities are stored as MongoDB documents, with AccountRepository extending MongoRepository for data access. Business logic, such as creating accounts and processing transactions, resides in the AccountService class, while AccountController manages API requests. Custom exceptions like InsufficientFundsException and AccountNotFoundException enhance error handling, ensuring a smooth transaction flow.

Project Folder Structure and Classes

1. Project Structure Overview: "Our project follows a standard Spring Boot structure. The main components are divided into specific packages for better organization and maintainability."
2. Main Application Class Purpose: This is the entry point of the Spring Boot application. Explanation: "The BankingSystemApplication class contains the main method which bootstraps the Spring Boot application." "It uses the @SpringBootApplication annotation, which combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations, simplifying configuration."
3. Model (Entity) Classes Account.java Purpose: Represents the bank account entity. Explanation: "The Account class is annotated with @Document, indicating it's a MongoDB document. It contains fields like accountNumber, accountHolderName, balance, and a list of transactions." "This class maps to a MongoDB collection and represents an account in our system." Transaction.java Purpose: Represents a transaction entity. Explanation: "The Transaction class contains fields such as type, amount, and timestamp, representing a single transaction (either deposit or withdrawal)."
4. Repository Interfaces AccountRepository.java Purpose: Data access layer for Account entities. Explanation: "The AccountRepository interface extends MongoRepository, providing CRUD operations for Account entities." "By using an interface, we leverage Spring Data's capability to generate the implementation at runtime. This allows us to focus on business logic rather than boilerplate code." "It includes a custom method findByAccountNumber to fetch accounts by their account number."
5. Service Classes AccountService.java Purpose: Contains business logic for account operations. Explanation: "The AccountService class is annotated with @Service, indicating it's a service component." "It uses the AccountRepository to perform operations like creating accounts, deposits, withdrawals, fund transfers, and fetching transaction history." "Service classes help separate business logic from controller code, promoting a cleaner architecture and easier testing."
6. Controller Classes AccountController.java Purpose: Handles HTTP requests and maps them to service methods. Explanation: "The AccountController class is annotated with @RestController and handles API endpoints under /api/accounts." "It includes endpoints for creating accounts, depositing money, withdrawing money, transferring funds, checking balance, and viewing transaction history." "Controllers handle request routing, while services perform the actual business logic."
7. Custom Exception Classes InsufficientFundsException.java Purpose: Custom exception for insufficient funds scenario. Explanation: "This exception is thrown when an account does not have enough balance to perform a withdrawal or transfer." AccountNotFoundException.java Purpose: Custom exception for account not found scenario. Explanation: "This exception is thrown when an account with a specified number does not exist." Explaining Interfaces vs. Normal Classes
8. Why Use Interfaces (e.g., AccountRepository)? Abstraction: "Interfaces provide a way to define the contract for the data access layer without being tied to a specific implementation." Spring Data Integration: "By extending MongoRepository, we let Spring Data generate the implementation for us, reducing boilerplate code and focusing on business logic." Flexibility: "Interfaces allow us to easily switch implementations if needed, without changing the service layer."
9. How It Helps: Ease of Testing: "Using interfaces makes it easier to write unit tests by mocking dependencies. For example, we can mock the AccountRepository in our tests to isolate service logic." Separation of Concerns: "It promotes a cleaner separation between the data access layer and the business logic, making the codebase more modular and maintainable." Summary Project Structure: Organized into packages like model, repository, service, controller, and exception for better modularity. Main Class: Bootstraps the Spring Boot application. Model Classes: Define the entities Account and Transaction. Repository Interfaces: Extend MongoRepository for CRUD operations, leveraging Spring Data's automatic implementation. Service Classes: Contain business logic, interacting with repositories.