Spring Boot: Exception Handling Best Practices

Let’s provide a more detailed explanation for the real-life example of throwing custom exceptions from a service layer and handling them globally in a Spring Boot application for a product-related scenario.
Steps:

1. Create a Custom ProductNotFoundException:

In this step, we create a custom exception class, ProductNotFoundException, which extends RuntimeException. This custom exception is used to represent situations where a product is not found in the system. By creating a custom exception, we can provide more specific information about the error.

public class ProductNotFoundException extends RuntimeException {
 public ProductNotFoundException(Long productId) {
 super(“Product not found with ID: “ + productId);
 }
}

Explanation:

Custom exceptions are used to capture application-specific error scenarios.
In this case, we include the productId in the exception message to provide detailed information about the missing product.

2. Create a Product Service:

Here, we create a ProductService class responsible for fetching product information. If a product is not found, it throws a ProductNotFoundException.

@Service
public class ProductService {

    public Product getProductById(Long productId) {
        // Simulate product retrieval logic
        Product product = getProductFromDatabase(productId);
        
        if (product == null) {
            throw new ProductNotFoundException(productId);
        }
        
        return product;
    }

    // Simulated method to fetch a product from a database
    private Product getProductFromDatabase(Long productId) {
        // Implement your database logic here
        // Return null if the product is not found
        return null;
    }
}

Explanation:

The ProductService encapsulates the business logic related to products.
The getProductById method simulates fetching a product from a database or another data source.
If the product is not found (based on the simulation), it throws a ProductNotFoundException.

3. Create a Global Exception Handler:

This step involves creating a global exception handler using @ControllerAdvice. The handler is responsible for catching ProductNotFoundException globally and returning a custom error response.

Spring Boot: Exception Handling Best Practices

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