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.