@ExceptionHandler in controllers in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @ExceptionHandler annotation in Spring Boot controllers?

It is used to define a method that handles specific exceptions thrown within the controller, allowing custom error responses without crashing the app.

beginner

How do you specify which exception a method handles using @ExceptionHandler?

You pass the exception class as a parameter to <code>@ExceptionHandler</code>, for example: <code>@ExceptionHandler(NullPointerException.class)</code>.

intermediate

Can @ExceptionHandler methods return custom HTTP status codes?

Yes, by returning a ResponseEntity or using @ResponseStatus on the method, you can set custom HTTP status codes for error responses.

intermediate

Where can @ExceptionHandler methods be declared in a Spring Boot app?

They can be declared inside a controller class or in a separate class annotated with <code>@ControllerAdvice</code> to handle exceptions globally.

beginner

What happens if no @ExceptionHandler matches an exception thrown in a controller?

Spring Boot uses its default error handling, which usually returns a generic error page or JSON with status 500 Internal Server Error.

What does @ExceptionHandler do in a Spring Boot controller?

A Configures database connections

B Defines a new REST endpoint

C Injects dependencies into the controller

D Handles specific exceptions thrown in the controller

@ExceptionHandler is used to catch and handle exceptions in controller methods.

How do you specify which exception a method handles with @ExceptionHandler?

A By passing the exception class to the annotation

B By naming the method after the exception

C By returning a ResponseEntity

D By using <code>@ResponseBody</code>

You specify the exception class inside @ExceptionHandler(ExceptionClass.class).

Where can @ExceptionHandler methods be placed?

A Only inside controller classes

B Inside controllers or classes annotated with <code>@ControllerAdvice</code>

C Only inside service classes

D Only in configuration classes

@ExceptionHandler methods can be in controllers or global handler classes with @ControllerAdvice.

What is the default HTTP status code if an exception is not handled by @ExceptionHandler?

A 500 Internal Server Error

B 404 Not Found

C 200 OK

D 302 Redirect

Unhandled exceptions usually result in a 500 Internal Server Error response.

How can you customize the HTTP status code returned by an @ExceptionHandler method?

A By naming the method with the status code

B By using <code>@GetMapping</code>

C By returning a <code>ResponseEntity</code> with status

D By throwing another exception

Returning a ResponseEntity lets you set the HTTP status code explicitly.

Explain how @ExceptionHandler works in Spring Boot controllers and how it helps improve user experience.

Think about how apps show friendly error messages instead of crashing.

Describe where and how you would use @ExceptionHandler to handle a NullPointerException in a Spring Boot app.

Imagine you want to catch a specific error and show a nice message.