Spring Boot Validation and Error Handling 2

Question 1

Which Spring class can be extended to override the default handling of standard Spring MVC exceptions and return custom error responses?

Accepted Answer

ResponseEntityExceptionHandler

Answer

ResponseEntityExceptionHandler is a convenient base class with @ExceptionHandler methods for standard Spring MVC exceptions that can be overridden to customize the error response.

Question 2

What is the purpose of the @ResponseStatus annotation when placed on a custom exception class?

Accepted Answer

It maps the exception to a specific HTTP status code returned when the exception is thrown

Answer

@ResponseStatus on an exception class (or @ExceptionHandler method) instructs Spring to respond with the specified HTTP status code whenever that exception propagates to the dispatcher.

Question 3

In Spring Boot 3+, which RFC standard does ProblemDetail implement for structured error responses?

Accepted Answer

RFC 7807 (Problem Details for HTTP APIs)

Answer

ProblemDetail, introduced in Spring 6 / Spring Boot 3, implements RFC 7807 which defines a standard JSON/XML format for machine-readable HTTP error responses.

Question 4

When validation fails on a @PathVariable or @RequestParam (not @RequestBody), which exception is thrown?

Accepted Answer

ConstraintViolationException

Answer

When Bean Validation constraints are violated on @PathVariable or @RequestParam parameters (requires @Validated on the class), a ConstraintViolationException is thrown rather than MethodArgumentNotValidException.

Question 5

How can you customize the default validation error message for a constraint such as @NotNull?

Accepted Answer

Provide a ValidationMessages.properties file on the classpath with the constraint key

Answer

Bean Validation reads message interpolation keys from ValidationMessages.properties on the classpath; defining javax.validation.constraints.NotNull.message overrides the default.

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Spring Boot Validation and Error Handling 2