Polish contribution

See gh-19901

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/reactive/error/DefaultErrorAttributes.java

@@ -81,39 +81,37 @@ public class DefaultErrorAttributes implements ErrorAttributes {
 		errorAttributes.put("timestamp", new Date());
 		errorAttributes.put("path", request.path());
 		Throwable error = getError(request);
-		HttpStatus errorStatus = determineHttpStatus(error);
+		ResponseStatus responseStatus = AnnotatedElementUtils.findMergedAnnotation(error.getClass(),
+				ResponseStatus.class);
+		HttpStatus errorStatus = determineHttpStatus(error, responseStatus);
 		errorAttributes.put("status", errorStatus.value());
 		errorAttributes.put("error", errorStatus.getReasonPhrase());
-		errorAttributes.put("message", determineMessage(error));
+		errorAttributes.put("message", determineMessage(error, responseStatus));
 		handleException(errorAttributes, determineException(error), includeStackTrace);
 		return errorAttributes;
 	}
 
-	private HttpStatus determineHttpStatus(Throwable error) {
+	private HttpStatus determineHttpStatus(Throwable error, ResponseStatus responseStatus) {
 		if (error instanceof ResponseStatusException) {
 			return ((ResponseStatusException) error).getStatus();
 		}
-		ResponseStatus responseStatus = AnnotatedElementUtils.findMergedAnnotation(error.getClass(),
-				ResponseStatus.class);
 		if (responseStatus != null) {
 			return responseStatus.code();
 		}
 		return HttpStatus.INTERNAL_SERVER_ERROR;
 	}
 
-	private String determineMessage(Throwable error) {
+	private String determineMessage(Throwable error, ResponseStatus responseStatus) {
 		if (error instanceof WebExchangeBindException) {
 			return error.getMessage();
 		}
 		if (error instanceof ResponseStatusException) {
 			return ((ResponseStatusException) error).getReason();
 		}
-		ResponseStatus responseStatus = AnnotatedElementUtils.findMergedAnnotation(error.getClass(),
-				ResponseStatus.class);
-		if (responseStatus != null) {
+		if (responseStatus != null && StringUtils.hasText(responseStatus.reason())) {
 			return responseStatus.reason();
 		}
-		return error.getMessage();
+		return (error.getMessage() != null) ? error.getMessage() : "";
 	}
 
 	private Throwable determineException(Throwable error) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/reactive/error/DefaultErrorAttributesTests.java

@@ -94,7 +94,7 @@ public class DefaultErrorAttributesTests {
 	}
 
 	@Test
-	void annotatedResponseStatusCodeWithExceptionMessage() {
+	public void annotatedResponseStatusCodeWithExceptionMessage() {
 		Exception error = new CustomException("Test Message");
 		MockServerHttpRequest request = MockServerHttpRequest.get("/test").build();
 		Map<String, Object> attributes = this.errorAttributes.getErrorAttributes(buildServerRequest(request, error),