public MimeType resolve(Map<String,Object> headers) {
		Object value = headers.get(MessageHeaders.CONTENT_TYPE);
		if (value instanceof MimeType) {
			return (MimeType) value;
		}
		else if (value instanceof String) {
			MimeType mimeType = mimeTypeCache.get(value);
			if (mimeType == null) {
				String valueAsString = (String) value;
				mimeType = MimeType.valueOf(valueAsString);
				mimeTypeCache.put(valueAsString,mimeType);
			}
			return mimeType;
		}
		return getDefaultMimeType();
	}
A {@link DefaultContentTypeResolver} that can parse String values.

@author David Turanski
spring-xd-messagebus-spi/src/main/java/org/springframework/xd/dirt/integration/bus/StringConvertingContentTypeResolver.java