Custom exception classes in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom exception class in Spring Boot?

A custom exception class is a user-defined class that extends Java's Exception or RuntimeException to represent specific error conditions in a Spring Boot application.

beginner

Why create custom exception classes instead of using standard exceptions?

Custom exceptions help clearly identify and handle specific error cases, making the code easier to read, maintain, and debug.

beginner

How do you define a simple custom exception class in Spring Boot?

Create a class that extends RuntimeException and add constructors. For example:<br><pre>public class ResourceNotFoundException extends RuntimeException {<br>  public ResourceNotFoundException(String message) {<br>    super(message);<br>  }<br>}</pre>

intermediate

How can custom exceptions improve REST API error responses in Spring Boot?

By using @ControllerAdvice and @ExceptionHandler, you can catch custom exceptions and return meaningful HTTP status codes and messages to clients.

intermediate

What is the difference between checked and unchecked exceptions in the context of custom exceptions?

Checked exceptions extend Exception and must be declared or caught. Unchecked exceptions extend RuntimeException and do not require explicit handling. Custom exceptions are usually unchecked for cleaner code.

Which class should you extend to create an unchecked custom exception in Spring Boot?

A Exception

B RuntimeException

C Throwable

D Error

Unchecked exceptions extend RuntimeException, so extending RuntimeException creates an unchecked custom exception.

What annotation is commonly used to globally handle custom exceptions in Spring Boot?

A @ControllerAdvice

B @RestController

C @Service

D @Component

@ControllerAdvice allows centralized exception handling across all controllers.

Which method is used inside a custom exception class to pass an error message?

A toString()

B getMessage()

C printStackTrace()

D super(message)

Calling super(message) in the constructor passes the error message to the parent Exception class.

Why might you prefer unchecked exceptions for custom exceptions in Spring Boot?

A They force callers to handle exceptions explicitly.

B They are slower to execute.

C They simplify code by not requiring try-catch blocks.

D They cannot be caught.

Unchecked exceptions do not require explicit handling, making code cleaner and easier to maintain.

What HTTP status code is typically returned when a ResourceNotFoundException is thrown in a REST API?

A 404 Not Found

B 400 Bad Request

C 500 Internal Server Error

D 200 OK

404 Not Found indicates the requested resource does not exist.

Explain how to create and use a custom exception class in a Spring Boot REST API.

Think about how exceptions improve error clarity and API responses.

Describe the benefits of using custom exceptions over standard exceptions in Spring Boot applications.

Consider how custom exceptions help both developers and users.