ResponseEntityExceptionHandler in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to extend the class for handling exceptions globally.

Spring Boot

public class GlobalExceptionHandler extends [1] { }

Drag options to blanks, or click blank then click option'

AException

BResponseEntityExceptionHandler

CRuntimeException

DControllerAdvice

Attempts:

3 left

💡 Hint

Common Mistakes

Extending Exception or RuntimeException instead of ResponseEntityExceptionHandler

Using @ControllerAdvice as a class to extend

The class should extend ResponseEntityExceptionHandler to customize exception handling in Spring Boot.

2fill in blank

medium

Complete the annotation to mark the class as a global exception handler.

Spring Boot

@[1]
public class GlobalExceptionHandler extends ResponseEntityExceptionHandler { }

Drag options to blanks, or click blank then click option'

ARestController

BService

CControllerAdvice

DComponent

Attempts:

3 left

💡 Hint

Common Mistakes

Using @RestController instead of @ControllerAdvice

Forgetting to annotate the class

The @ControllerAdvice annotation marks the class to handle exceptions globally across controllers.

3fill in blank

hard

Fix the method signature to override the handler for MethodArgumentNotValidException.

Spring Boot

@Override
protected ResponseEntity<Object> handleMethodArgumentNotValid(
    MethodArgumentNotValidException [1],
    HttpHeaders headers, HttpStatus status, WebRequest request) {
    // method body
}

Drag options to blanks, or click blank then click option'

Aerror

Bexception

Ce

Dex

Attempts:

3 left

💡 Hint

Common Mistakes

Using parameter names that don't match the override signature

Missing the @Override annotation

The parameter name can be anything, but ex is commonly used and matches the override signature.

4fill in blank

hard

Fill both blanks to create a ResponseEntity with a custom error message and BAD_REQUEST status.

Spring Boot

return new ResponseEntity<>([1], [2]);

Drag options to blanks, or click blank then click option'

AerrorDetails

BHttpStatus.BAD_REQUEST

CHttpStatus.NOT_FOUND

DresponseBody

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of arguments

Using wrong HTTP status codes

The first blank is the body object (like errorDetails), and the second blank is the HTTP status HttpStatus.BAD_REQUEST.

5fill in blank

hard

Fill all three blanks to build a map of field errors inside the exception handler.

Spring Boot

Map<String, String> errors = new HashMap<>();
ex.getBindingResult().getFieldErrors().forEach(error -> {
    errors.put(error.getField(), [1]);
});
return new ResponseEntity<>([2], [3]);

Drag options to blanks, or click blank then click option'

Aerror.getDefaultMessage()

Berrors

CHttpStatus.BAD_REQUEST

Derror.getCode()

Attempts:

3 left

💡 Hint

Common Mistakes

Using error code instead of default message

Returning wrong status code

Not returning the errors map

The map stores field names and their default messages. Then the map is returned with BAD_REQUEST status.

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