Resteasy library is being very strict about the "Accepts" header matching. The ODta4J library when it defined the "$metadata" service it defined one of its "accept" headers as "application/xml;charset=utf-8".

When client issues a "$metadata" call for metadata service, the client uses "application/xml" (omits the charset=utf-8) as its "accept" header, Resteasy while matching the requests it does not like it, it expects EXACTLY same header like "application/xml;charser=utf-8" not even allows different case of the header like "applicatoin/xml;charset=UTF-8"