Low level design of car rental system with JAVA

Published On: 18 January 2024.By prashant gupta.

Low level design of car rental system with JAVA

In a Low-Level Design (LLD) for a car rental system, we’ll focus on the detailed design of specific modules and components. Let’s elaborate on the LLD for key components: Car Management, Customer Management, Booking System, Rental Management, Admin Dashboard, External Services Integration, Database Schema, Security Measures, and Error Handling.

UML Diagram:

Creating a complete UML (Unified Modeling Language) diagram for a car rental system involves several types of diagrams. Here, I’ll provide simplified versions of the Class Diagram, Use Case Diagram, and Sequence Diagrams for key interactions.

1. Class Diagram:

The Class Diagram represents the static structure of the car rental system, showing classes, attributes, and relationships.

In a real-world car rental system, the concepts of “booking” and “rental” can represent distinct stages or aspects of the rental process. Let me clarify the distinction between the two:

Booking Module:
- The Booking Module is responsible for handling the initial stage of the rental process. It involves customers searching for available cars, making reservations, and receiving a confirmation for their reservation. This module is mainly concerned with the reservation process, which may or may not lead to an actual rental.
Rental Module:
- The Rental Module comes into play after a booking has been confirmed. It manages the active rental period, calculates the total cost, and generates invoices. Once a customer picks up a reserved car, the reservation transitions into an active rental. The Rental Module tracks the ongoing rentals until the customer returns the car.

Separating the booking and rental processes into distinct modules allows for a more modular and organized system design. It also enables better management of reservations and active rentals, providing clarity in the flow of the system.

Here’s how the flow might look in a simplified manner:

Booking Flow:

Customer searches for available cars.
Customer makes a reservation (booking).
System confirms the booking and provides a booking ID.

Rental Flow:

Customer picks up the reserved car.
Rental period begins, and the system tracks the ongoing rental.
Customer returns the car.
Rental Module calculates the total cost and generates an invoice.

By having separate modules, you can encapsulate specific functionalities and manage the complexities of the rental process more effectively. However, the design can be adapted based on the specific requirements and complexities of the car rental system you are developing.

2. Use Case Diagram:

The Use Case Diagram illustrates the interactions between actors (users) and the system.

Actors:

Customer: Interacts with the system to search, book, and manage rentals.
Admin: Manages cars, customers, and bookings.

Use Cases:

Search and Book Cars: Customer can search for available cars and make bookings.
Manage Bookings: Customer can view and cancel bookings.
Manage Cars: Admin can add, update, and delete cars.
Manage Customers: Admin can view customer information.

3. Sequence Diagrams:

These Sequence Diagrams provide a dynamic view of interactions between objects over time.

Key Interactions:

Customer Books a Car:
- Customer searches for available cars.
- System returns a list of available cars.
- Customer selects a car and initiates the booking process.
- System validates the booking and confirms it.
Admin Manages Cars:
- Admin logs in and accesses the admin dashboard.
- Admin selects the “Manage Cars” option.
- System retrieves and displays the list of cars.
- Admin updates car information.

1. Car Management Module:

Class

public class Car {
private int carID;
private String brand;
private String model;
private int year;
private boolean available;
private int rentPerHour;

// Constructors, getters, setters, and other methods
}

public class Car {

private int carID;

private String brand;

private String model;

private int year;

private boolean available;

private int rentPerHour;

// Constructors, getters, setters, and other methods

}

Method:

public class CarManagementModule {
public void addCar(Car car);
public void updateCar(int carID, Car updatedCar);
public void deleteCar(int carID);
public List<Car> getAllCars();
public Car getCarByID(int carID);
public void updateCarAvailability(int carId, boolean availability);
}

public class CarManagementModule {

public void addCar(Car car);

public void updateCar(int carID, Car updatedCar);

public void deleteCar(int carID);

public List<Car> getAllCars();

public Car getCarByID(int carID);

public void updateCarAvailability(int carId, boolean availability);

}

2. Customer Management Module:

public class Customer {
private int customerID;
private String name;
private String contactInfo;

// Constructors, getters, setters, and other methods
}

public class Customer {

private int customerID;

private String name;

private String contactInfo;

// Constructors, getters, setters, and other methods

}

public class CustomerManagementModule {
public void registerCustomer(Customer customer);
public Customer login(String contactInfo, String password);
public Customer getCustomerByID(int customerID);
}

public class CustomerManagementModule {

public void registerCustomer(Customer customer);

public Customer login(String contactInfo, String password);

public Customer getCustomerByID(int customerID);

}

3. Booking System Module:

public class Booking {
private int bookingID;
private int carID;
private int customerID;
private Date startDate;
private Date endDate;

// Constructors, getters, setters, and other methods
}

public class Booking {

private int bookingID;

private int carID;

private int customerID;

private Date startDate;

private Date endDate;

// Constructors, getters, setters, and other methods

}

public class BookingSystemModule {
public List<Car> checkAvailability(Date startDate, Date endDate);
public Booking makeBooking(int carID, int customerID, Date startDate, Date endDate);
public void cancelBooking(int bookingID);
}

public class BookingSystemModule {

public List<Car> checkAvailability(Date startDate, Date endDate);

public Booking makeBooking(int carID, int customerID, Date startDate, Date endDate);

public void cancelBooking(int bookingID);

}

4. Rental Management Module:

public class Rental {
private int rentalID;
private int bookingID;
private double totalCost;
// Constructors, getters, setters, and other methods

}

public class Rental {

private int rentalID;

private int bookingID;

private double totalCost;

// Constructors, getters, setters, and other methods

}

public class RentalManagementModule {

public double calculateCost(int bookingID);
public Rental generateInvoice(int bookingID);

public void markCarUnavailabile(carId);
public void markCarAvailabile(carId);

// If customer return the vehicle earlier or extend the duration
public void updateEndDateForBooking(int bookingID); 
}

public class RentalManagementModule {

public double calculateCost(int bookingID);

public Rental generateInvoice(int bookingID);

public void markCarUnavailabile(carId);

public void markCarAvailabile(carId);

// If customer return the vehicle earlier or extend the duration

public void updateEndDateForBooking(int bookingID);

}

5. Admin Dashboard Module:

public class AdminDashboard {
// Methods for monitoring bookings, managing cars, and customers
}

public class AdminDashboard {

// Methods for monitoring bookings, managing cars, and customers

}

6. External Services Integration:

Payment Gateway Integration:

public class PaymentGatewayService { public boolean processPayment(String cardNumber, double amount); }

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public class PaymentGatewayService {
public boolean processPayment(String cardNumber, double amount);
}
Notification Service Integration:

public class NotificationService { public void sendNotification(String recipient, String message); }

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public class NotificationService {
public void sendNotification(String recipient, String message);
}
Mapping Service Integration:

public class MappingService { public Location getCarLocation(int carID); }

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public class MappingService {
public Location getCarLocation(int carID);
}

7. Database Schema:

Tables for cars, customers, bookings, rentals with appropriate relationships.

8. Security Measures:

Use JWT for user authentication.
Implement HTTPS for secure communication.
Encrypt sensitive data like passwords.

9. Error Handling:

Define error codes and messages.
Implement exception handling mechanisms.

Conclusion:

This Low-Level Design provides a more detailed view of the classes, methods, and interactions within each module of the car rental system. It’s crucial to tailor the design to specific requirements, considering the technology stack and overall system architecture. Additionally, continuous refinement and updates to the design may be necessary during the implementation phase.