ResponseEntityExceptionHandler in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

How does ResponseEntityExceptionHandler handle exceptions?

Consider a Spring Boot controller that throws a MethodArgumentNotValidException. How does ResponseEntityExceptionHandler respond by default?

A It returns a 404 Not Found error without any body.

B It returns a 500 Internal Server Error with a generic message.

C It returns a 400 Bad Request with a detailed error body explaining validation failures.

D It ignores the exception and lets the request succeed.

💡 Hint

Think about what HTTP status code is appropriate for invalid input.

ResponseEntityExceptionHandler provides built-in handling for common exceptions like MethodArgumentNotValidException. It returns a 400 status with details about what validation failed.

📝 Syntax

intermediate

Correct override of handleHttpMessageNotReadable

Which method signature correctly overrides handleHttpMessageNotReadable in a class extending ResponseEntityExceptionHandler?

A public ResponseEntity<Object> handleHttpMessageNotReadable(HttpMessageNotReadableException ex, HttpHeaders headers, HttpStatusCode status, WebRequest request)

B protected ResponseEntity<Object> handleHttpMessageNotReadable(HttpMessageNotReadableException ex, HttpHeaders headers, HttpStatusCode status, WebRequest request)

C protected ResponseEntity<Object> handleHttpMessageNotReadable(HttpMessageNotReadableException ex, HttpHeaders headers, HttpStatus status, WebRequest request)

D protected ResponseEntity<Object> handleHttpMessageNotReadable(Exception ex, HttpHeaders headers, HttpStatusCode status, WebRequest request)

💡 Hint

Check the exact parameter types and access modifier in the superclass method.

The method to override uses protected access and HttpStatusCode for the status parameter in Spring Boot 3+. The exception type must be HttpMessageNotReadableException.

🔧 Debug

advanced

Why does custom exception handler not get called?

You created a class extending ResponseEntityExceptionHandler and annotated it with @ControllerAdvice. But your custom handleMethodArgumentNotValid method is never called. What is the most likely cause?

A The method signature does not exactly match the superclass method signature.

B The exception is not thrown by any controller method.

C You forgot to add <code>@ExceptionHandler</code> annotation on the method.

D The class is missing <code>@RestControllerAdvice</code> annotation instead of <code>@ControllerAdvice</code>.

💡 Hint

Check method signatures carefully when overriding methods.

Overriding methods must match the exact signature of the superclass method. If the signature differs, the method will not override and will not be called.

❓ state_output

advanced

What is the HTTP status code returned by default for UnsupportedMediaTypeException?

When a controller receives a request with an unsupported media type, and ResponseEntityExceptionHandler handles HttpMediaTypeNotSupportedException, what HTTP status code is returned by default?

A 406 Not Acceptable

B 400 Bad Request

C 500 Internal Server Error

D 415 Unsupported Media Type

💡 Hint

Think about the meaning of the status codes related to media types.

The HttpMediaTypeNotSupportedException is handled by returning 415 status code, which means the media type is not supported by the server.

🧠 Conceptual

expert

Why extend ResponseEntityExceptionHandler instead of using @ExceptionHandler alone?

In Spring Boot, what is the main advantage of extending ResponseEntityExceptionHandler in your @ControllerAdvice class compared to only defining @ExceptionHandler methods?

A It provides default handling for many common Spring MVC exceptions, reducing boilerplate code.

B It forces all exceptions to return HTTP 200 status.

C It disables the default Spring Boot error page and replaces it with a blank response.

D It automatically logs all exceptions without extra code.

💡 Hint

Think about what ResponseEntityExceptionHandler already implements for you.

Extending ResponseEntityExceptionHandler gives you ready-made handlers for many exceptions like validation errors, media type errors, etc. This saves you from writing repetitive code.

Practice

1. What is the main purpose of ResponseEntityExceptionHandler in a Spring Boot application?

easy

A. To handle user authentication and authorization

B. To centralize and customize error handling for REST controllers

C. To manage database connections automatically

D. To configure application properties at runtime

Solution

1. Step 1: Understand the role of ResponseEntityExceptionHandler

   This class provides a centralized way to handle exceptions thrown by REST controllers in Spring Boot.

2. Step 2: Compare with other options

   Options A, B, and D relate to authentication, database management, and configuration, which are not the responsibility of ResponseEntityExceptionHandler.

3. Final Answer:

   To centralize and customize error handling for REST controllers -> Option B

4. Quick Check:

   ResponseEntityExceptionHandler centralizes REST error handling [OK]

Hint: Remember: ResponseEntityExceptionHandler handles REST errors centrally [OK]

Common Mistakes:

• Confusing it with security or database management
• Thinking it configures app properties
• Assuming it handles UI rendering errors

2. Which method signature correctly overrides a method from ResponseEntityExceptionHandler to handle MethodArgumentNotValidException?

easy

A. protected ResponseEntity<Object> handleValidationException(Exception ex, HttpHeaders headers, HttpStatus status, WebRequest request)

B. public void handleMethodArgumentNotValid(Exception ex)

C. private ResponseEntity<String> handleValidationError(MethodArgumentNotValidException ex)

D. protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex, HttpHeaders headers, HttpStatus status, WebRequest request)

Solution

1. Step 1: Check method signature requirements

   ResponseEntityExceptionHandler requires protected method returning ResponseEntity<Object> with parameters (MethodArgumentNotValidException, HttpHeaders, HttpStatus, WebRequest).

2. Step 2: Match options to signature

   protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex, HttpHeaders headers, HttpStatus status, WebRequest request) matches exactly. Options B and C have wrong access modifiers or parameters. protected ResponseEntity<Object> handleValidationException(Exception ex, HttpHeaders headers, HttpStatus status, WebRequest request) uses wrong exception type and method name.

3. Final Answer:

   protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex, HttpHeaders headers, HttpStatus status, WebRequest request) -> Option D

4. Quick Check:

   Exact override signature required [OK]

Hint: Override with exact signature including all parameters [OK]

Common Mistakes:

• Using wrong access modifier like public or private
• Missing parameters like HttpHeaders or WebRequest
• Changing return type to something other than ResponseEntity<Object>

3. Given this code snippet inside a class extending ResponseEntityExceptionHandler:

  @Override
  protected ResponseEntity<Object> handleHttpMessageNotReadable(HttpMessageNotReadableException ex, HttpHeaders headers, HttpStatus status, WebRequest request) {
      String body = "Malformed JSON request";
      return new ResponseEntity<>(body, headers, HttpStatus.BAD_REQUEST);
  }

What will be the HTTP status code returned when a malformed JSON is sent to the API?

medium

A. 200 OK

B. 500 Internal Server Error

C. 400 Bad Request

D. 404 Not Found

Solution

1. Step 1: Analyze the overridden method

   The method returns a ResponseEntity with status HttpStatus.BAD_REQUEST when JSON is malformed.

2. Step 2: Identify the HTTP status code for BAD_REQUEST

   BAD_REQUEST corresponds to HTTP status code 400.

3. Final Answer:

   400 Bad Request -> Option C

4. Quick Check:

   BAD_REQUEST = 400 [OK]

Hint: BAD_REQUEST means 400 status code [OK]

Common Mistakes:

• Confusing BAD_REQUEST with 500 Internal Server Error
• Assuming 200 OK is returned on error
• Mixing up 404 Not Found with validation errors

4. Consider this custom exception handler class:

  @ControllerAdvice
  public class CustomExceptionHandler extends ResponseEntityExceptionHandler {

      @ExceptionHandler(NullPointerException.class)
      public ResponseEntity<Object> handleNullPointer(NullPointerException ex, WebRequest request) {
          String body = "Null value found";
          return new ResponseEntity<>(body, HttpStatus.INTERNAL_SERVER_ERROR);
      }

      @Override
      protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex, HttpHeaders headers, HttpStatus status, WebRequest request) {
          String body = "Validation failed";
          return new ResponseEntity<>(body, HttpStatus.BAD_REQUEST);
      }
  }

If a NullPointerException occurs, what will be the HTTP status code returned?

medium

A. 500 Internal Server Error

B. 400 Bad Request

C. 404 Not Found

D. 200 OK

Solution

1. Step 1: Identify the handler for NullPointerException

   The method annotated with @ExceptionHandler(NullPointerException.class) returns status INTERNAL_SERVER_ERROR.

2. Step 2: Map INTERNAL_SERVER_ERROR to HTTP status code

   INTERNAL_SERVER_ERROR corresponds to HTTP status 500.

3. Final Answer:

   500 Internal Server Error -> Option A

4. Quick Check:

   NullPointerException handled with 500 status [OK]

Hint: Check @ExceptionHandler annotation for exception type [OK]

Common Mistakes:

• Assuming validation error handler is called for NullPointerException
• Confusing 400 Bad Request with 500 Internal Server Error
• Ignoring @ExceptionHandler methods

5. You want to customize error responses for both validation errors and JSON parse errors in your Spring Boot REST API. Which approach correctly combines ResponseEntityExceptionHandler methods and @ExceptionHandler to achieve this?

hard

A. Override handleMethodArgumentNotValid for validation errors and add an @ExceptionHandler for HttpMessageNotReadableException

B. Use only @ExceptionHandler methods for all exceptions, no overrides needed

C. Override handleHttpMessageNotReadable for validation errors and use @ExceptionHandler for MethodArgumentNotValidException

D. Override handleExceptionInternal to catch all exceptions globally

Solution

1. Step 1: Understand which methods handle which exceptions

   handleMethodArgumentNotValid handles validation errors; handleHttpMessageNotReadable handles JSON parse errors.

2. Step 2: Combine overrides and @ExceptionHandler correctly

   Override handleMethodArgumentNotValid for validation errors and use @ExceptionHandler for HttpMessageNotReadableException to customize JSON parse error responses.

3. Final Answer:

   Override handleMethodArgumentNotValid for validation errors and add an @ExceptionHandler for HttpMessageNotReadableException -> Option A

4. Quick Check:

   Use overrides for validation, @ExceptionHandler for JSON errors [OK]

Hint: Override validation method, @ExceptionHandler for JSON parse errors [OK]

Common Mistakes:

• Mixing exception types in wrong handlers
• Using only @ExceptionHandler without overrides
• Overriding wrong methods for given exceptions