Spring boot 2.0.1 - Actuator endpoint failing when content negotiation`favorPathExtension` set as true

[JagmohanSharma]

Getting error of HTTP ERROR 406 Not acceptable content, when using spring boot 2.0.1.

when we set favorPathExtension to true , then we get HTTP ERROR 406 Not acceptable content for each actuator endpoint.

but it was working fine with spring boot 2.0.0.

As now in spring boot 2.0.1, we have defined order for WebMvcAutoConfigurationAdapter to be executed at higher precedence so that any custom configuration get executed after this.

But it is causing issue for actuator endpoint when we set favorPathExtension as true.

[JagmohanSharma]

When we set favorPathExtension to true , only 'HeaderContentNegotiationStrategy' is getting executed but not PathExtensionContentNegotiationStrategy as per favorPathExtension value as true Or any other default configured strategy. So we get 406 error.

I found one java doc comment which seems relevant:

<strong>Note:</strong> if you must use URL-based content type resolution,
 * the use of a query parameter is simpler and preferable to the use of a path
 * extension since the latter can cause issues with URI variables, path
 * parameters, and URI decoding. Consider setting {@link #setFavorPathExtension}
 * to {@literal false} or otherwise set the strategies to use explicitly via
 * {@link #setStrategies(List)}.

is this meant to use setStrategies(List) method when ever we set favorPathExtension as true?

[philwebb]

@JagmohanSharma Is this for any actuator endpoint or some custom ones that you're developing? Do you have a sample application that we can run for ourselves to see what you mean?

[JagmohanSharma]

@philwebb This is for actuator endpoints. Please find sample code here https://github.com/JagmohanSharma/SpringBoot2Issues. I added custom content negotiation configuration but disabled it. Now it is a plain spring boot configured and have set spring.mvc.contentnegotiation.favor-path-extension=true with spring boot 2.0.1. So here test ContentNegotiationTest is getting failed where I am executing info endpoint.

This works fine if we use spring boot 2.0.0 OR set spring.mvc.contentnegotiation.favor-path-extension=false with 2.0.1 itself.

[JagmohanSharma]

@philwebb I found some more info regarding this issue.

In WebMvcAutoConfigurationAdapter: OptionalPathExtensionContentNegotiationStrategy, we have below method which returns empty list if SKIP_ATTRIBUTE is set as true or not set.

@Override
public List<MediaType> resolveMediaTypes(NativeWebRequest webRequest)
		throws HttpMediaTypeNotAcceptableException {
	Object skip = webRequest.getAttribute(SKIP_ATTRIBUTE,
			RequestAttributes.SCOPE_REQUEST);
	if (skip != null && Boolean.parseBoolean(skip.toString())) {
		return Collections.emptyList();
	}
	return this.delegate.resolveMediaTypes(webRequest);
}

Now in ContentNegotiationManager, if we get empty list then it simply returns that and any other strategy will not be executed.

@Override
public List<MediaType> resolveMediaTypes(NativeWebRequest request) throws HttpMediaTypeNotAcceptableException {
	for (ContentNegotiationStrategy strategy : this.strategies) {
		List<MediaType> mediaTypes = strategy.resolveMediaTypes(request);
		if (mediaTypes.equals(MEDIA_TYPE_ALL_LIST)) {
			continue;
		}
		return mediaTypes;
	}
	return MEDIA_TYPE_ALL_LIST;
}

this is called from AbstractMessageConverterMethodProcessor while executing below code for getting AcceptableMediaTypes which we get as empty list from ContentNegotiationManager

else {
	HttpServletRequest request = inputMessage.getServletRequest();
	List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(request);

SO we get exception while comparing this acceptable media type with producible media types in AbstractMessageConverterMethodProcessor

HttpServletRequest request = inputMessage.getServletRequest();
List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(request);
List<MediaType> producibleMediaTypes = getProducibleMediaTypes(request, valueType, declaredType);

if (outputValue != null && producibleMediaTypes.isEmpty()) {
	throw new HttpMessageNotWritableException(
			"No converter found for return value of type: " + valueType);
}
mediaTypesToUse = new ArrayList<>();
for (MediaType requestedType : requestedMediaTypes) {
	for (MediaType producibleType : producibleMediaTypes) {
		if (requestedType.isCompatibleWith(producibleType)) {
			mediaTypesToUse.add(getMostSpecificMediaType(requestedType, producibleType));
		}
	}
}
if (mediaTypesToUse.isEmpty()) {
	if (outputValue != null) {
		throw new HttpMediaTypeNotAcceptableException(producibleMediaTypes);
	}
	return;
}