MappingJackson2XmlHttpMessageConverter should support non UTF charsets

[mrpiggi]

I currently have to deal with a REST API using text/xml;charset=ISO-8859-1 as MediaType. So just using MappingJackson2XmlHttpMessageConverter seemed obvious to me. Unfortunately I found myself with

RestClientException: No HttpMessageConverter for ... and content type "text/xml;charset=ISO-8859-1"

As it turns out, inheriting from AbstractJackson2HttpMessageConverter checks for hard-coded UTF encodings when calling MappingJackson2XmlHttpMessageConverter.canWrite()

spring-framework/spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

Lines 84 to 92 in 65553f5

	private static final Map<String, JsonEncoding> ENCODINGS;
	static {
	ENCODINGS = CollectionUtils.newHashMap(JsonEncoding.values().length);
	for (JsonEncoding encoding : JsonEncoding.values()) {
	ENCODINGS.put(encoding.getJavaName(), encoding);
	}
	ENCODINGS.put("US-ASCII", JsonEncoding.UTF8);
	}

spring-framework/spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

Lines 273 to 283 in 65553f5

	public boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType) {
	if (!canWrite(mediaType)) {
	return false;
	}
	if (mediaType != null && mediaType.getCharset() != null) {
	Charset charset = mediaType.getCharset();
	if (!ENCODINGS.containsKey(charset.name())) {
	return false;
	}
	}
	ObjectMapper objectMapper = selectObjectMapper(clazz, mediaType);

which is totally reasonable for JSON but not for XML. Overriding this method is not a problem at all but I wanted you to be notified at least.

[sdeleuze]

After having a deeper look, I am going to decline this issue due to assumptions hardcoded in Jackson JsonEncoding, what was discussed in #25076 and given the fact FasterXML/jackson-dataformat-xml#315 is opened for years. There are workarounds possible but we would need to change totally the Jackson converter and codec hierarchy, so I prefer to wait for first-class support for that in Jackson.

For now, please use Jaxb2RootElementHttpMessageConverter if you have such need.

[mrpiggi]

I should have looked more carefully for old issues. Sorry about that. Thanks for pointing to
Jaxb2RootElementHttpMessageConverter that's exactly the way I went.

Sorry for the noise...