Springhard

How do you handle exceptions globally in Spring MVC?

Answer

Use `@ControllerAdvice` with `@ExceptionHandler` to map exceptions to consistent HTTP responses (status + body). It keeps controllers clean and centralizes error handling.

@ControllerAdvice
class ApiErrors {
  @ExceptionHandler(IllegalArgumentException.class)
  ResponseEntity<String> badRequest(IllegalArgumentException e) {
    return ResponseEntity.badRequest().body(e.getMessage());
  }
}

Advanced answer

Deep dive

Global exception handling in Spring MVC is commonly done with:

`@ControllerAdvice` (applies to MVC controllers)
`@RestControllerAdvice` (same, but handler return values are written to the response body by default)

You map exception types to HTTP responses using `@ExceptionHandler`. For rich responses, return `ResponseEntity<?>` (status, headers, body) or use `ProblemDetail` in newer Spring versions.

What to centralize

Consistent error shape (e.g., `errorCode`, `message`, `path`, `correlationId`).
Validation errors (`MethodArgumentNotValidException`) → field-level messages.
Logging + mapping internal exceptions to safe public messages.

Example

@RestControllerAdvice
class ApiErrors {
  @ExceptionHandler(IllegalArgumentException.class)
  ResponseEntity<ProblemDetail> badRequest(IllegalArgumentException e) {
    var pd = ProblemDetail.forStatus(400);
    pd.setTitle("Bad request");
    pd.setDetail(e.getMessage());
    return ResponseEntity.badRequest().body(pd);
  }
}

Common pitfalls

Leaking stack traces or internal messages to clients.
Returning different error shapes per controller.