Why REST call with xml payload enclosed with "DeferredDocumentImpl" (spring resttemplate) - spring

Question

I am making a rest call using restemplate and payload is XML. (we are dealing with legacy servers) But When I debug XML at server which is a spring application (legacy, but here irrelevant) , I see that the xml payload enclosed with "DeferredDocumentImpl"
Client code:
This is a new piece which is being added and is straightforward (so may be issue is here) Also I am testing by faking xml payload jsut to check parsing:
.....
String xmlString ="<?xml version=\"1.0\" ?>\n"
+ "<myroot>\n"
//node values
+ "</myroot>";
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(new InputSource(new StringReader(xml);
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.TEXT_XML);
HttpEntity<Document> request = new HttpEntity<>(document, headers);
final ResponseEntity<String> response = restTemplate.postForEntity(uri, request, String.class);
when I debugged outgoing call I see xml payload enclosed with "DeferredDocumentImpl"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "POST /myuri HTTP/1.1[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "Accept: text/plain, application/xml, text/xml, application/json, application/*+xml, application/*+json, */*[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "X-Forwarded-For: value[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "Content-Type: text/xml[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "Content-Length: 277[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "Host: localdev.stanfordhealthcare.org:8443[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "Connection: Keep-Alive[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "User-Agent: Apache-HttpClient/4.5.11 (Java/12.0.2)[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "Accept-Encoding: gzip,deflate[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "[\r][\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "<DeferredDocumentImpl><?xml version="1.0" encoding="UTF-16"?><myroot>[\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> " <notification>[\n]"
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> " <type>3</type>[\n]"
/////
22:17:02.879 [main] DEBUG org.apache.http.wire - http-outgoing-0 >> "</myroot></DeferredDocumentImpl>"
22:17:08.324 [poolScheduler1] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Closing expired connections
Server code :
This is a working production legacy code and it does process xml payload properly .So I dont think there is issue here as it process same xml payload from other clients.
#SuppressWarnings("unchecked")
public static <T> T parseRequestObject(Class<T> pojoClass, HttpServletRequest request) {
T pojoObject = null;
String xml = IOUtils.toString(request.getReader());
...
}
So here When I debug xml I see the xml payload enclosed with "DeferredDocumentImpl"
"<DeferredDocumentImpl><?xml version="1.0" encoding="UTF-16"?><myroot> <..></DeferredDocumentImpl>"
Q:I am not sure from where this "DeferredDocumentImpl" is coming and why and how to fix it.

Answer 1

I solved it and the error is in a because of legacy handling of payload).
It is a REST call but content acceptable is plain text (as xml) not as XML document!
HttpHeaders headers = new HttpHeaders();
headers.add("X-Forwarded-For", "value");
headers.setContentType(MediaType.TEXT_XML);
headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));//This is by default
HttpEntity<String> request = new HttpEntity<String>(xmlString, headers);