@ExceptionHandler(HttpMessageNotReadableException.class)
	@ResponseStatus(code = HttpStatus.BAD_REQUEST)
	public ResponseEntity<ErrorMessage> handleHttpMessageNotReadable(HttpMessageNotReadableException ex) {
		Throwable mostSpecificCause = ex.getMostSpecificCause();
		ErrorMessage errorMessage;
		if (mostSpecificCause != null) {
			String exceptionName = mostSpecificCause.getClass().getName();
			String message = mostSpecificCause.getMessage();
			errorMessage = new ErrorMessage(exceptionName, message);
		}
		else {
			errorMessage = new ErrorMessage(ex.getMessage());
		}
		return new ResponseEntity(errorMessage, HttpStatus.BAD_REQUEST);
	}
Note use base class if you wish to leverage its handling.
Some code will need changing.
springdoc-openapi-starter-webmvc-api/src/test/java/test/org/springdoc/api/v31/app110/GlobalControllerAdvice.java