Spring Boot Global Exception Handling with @ControllerAdvice

This project demonstrates how to implement global exception handling in a Spring Boot application using the @ControllerAdvice annotation. It showcases custom exception handling by defining a centralized mechanism for managing exceptions across the application.

Features

• Centralized exception handling using @ControllerAdvice
• Custom exception classes (CustomerNotFoundException)
• ResponseEntity customization for HTTP responses
• RESTful API endpoints for managing customers

---

Project Structure

The project follows a simple structure that separates the controller, entity, and exception-related files for better organization and maintainability:

Key Components

1. CustomerController

   • This class provides endpoints for retrieving all customers and individual customers by their ID.
   • If a requested customer is not found, it throws a CustomerNotFoundException.

2. GlobalExceptionHandler

   • The class uses the @ControllerAdvice annotation to define a global exception handler.
   • It captures any CustomerNotFoundException thrown by the controller and returns a structured exception response (in the form of an ExceptionObject).

3. ExceptionObject

   • This class represents the structure of the exception response. It contains:
     • message: The error message describing what went wrong.
     • timestamp: The time when the error occurred.
     • httpStatus: The HTTP status code associated with the error (e.g., NOT_FOUND).

4. CustomerNotFoundException

   • A custom exception class used to represent when a customer is not found in the system.

---

APIs

Get All Customers

Endpoint: /customers/all
Method: GET

This endpoint retrieves a list of all customers in the system.

Get Customer by ID

Endpoint: /customers/get/{customerId}
Method: GET

This endpoint retrieves a customer by their ID. If the customer with the given ID is not found, it will throw a CustomerNotFoundException and return a custom error response.

---

How It Works

1. CustomerController provides the REST API for fetching customer data.

   • GET /customers/all: Returns a list of all customers.
   • GET /customers/get/{customerId}: Fetches a specific customer by their ID.

2. GlobalExceptionHandler captures exceptions like CustomerNotFoundException and returns an error response containing:

   • message: The error message explaining the issue.
   • timestamp: The time the error occurred.
   • httpStatus: The HTTP status code (e.g., 404 NOT_FOUND).

3. ExceptionObject is the structure for the exception response, making it easy to return consistent and informative error details in case of an exception.

---

Example Usage

1. Fetch All Customers
   To fetch all customers, make a GET request to /customers/all. The response will return a list of customers in JSON format.

2. Fetch Customer by ID
   To fetch a customer by ID, make a GET request to /customers/get/{customerId}. If the customer is found, their details will be returned. If not, an error response will be returned indicating that the customer is not found.

---

Technologies Used

• Spring Boot: Framework for building the Java-based application.
• Spring Web: Module used to build RESTful web services.
• Spring Data JPA: Used for database interaction with the Customer entity.
• Lombok: Used to reduce boilerplate code like getters and setters.
• JPA: Used for ORM (Object-Relational Mapping) with the database.

---

Conclusion

This project demonstrates the use of Spring Boot’s @ControllerAdvice to handle exceptions globally. By centralizing exception handling in one place, it ensures consistent error responses and simplifies debugging. This setup allows for a more maintainable codebase by separating concerns and ensuring that error handling is both reusable and extensible.