How to use IBM MobileFirst java adapter to update existing entity? - ibm-mobilefirst

Question

The jax-rs resource method can get JSON which is part of document.
My issue is that I have to update existing object (entity). So I decided on creating jax-rs ContainerRequestFilter. This filter has to get existing object, replace its properties with new one and put it back to stream. Therefore I hope that I get entity completely in my resource method.
At first I has to get data for authenticated user. But 'securityContext.getAuthenticatedUser()' returns partially provided JSON data?
Is there any possibility to get authenticated user data in jax-rs filter (on ibm MobileFirst platform)?
There is the code of my filter:
#Provider
//#ManagedBean
public class UpdateFilter implements ContainerRequestFilter {
//ReaderInterceptor {
//#Inject
//ExistingObjectDao existingObjectDao;
#Context
AdapterSecurityContext securityContext;
#Override
#OAuthSecurity(scope = "protected") //doesn't work
public void filter(ContainerRequestContext context) throws IOException {
//context.getSecurityContext().getUserPrincipal() // is null
AuthenticatedUser user = securityContext.getAuthenticatedUser(); //is null
Map<String, String> authParams = (Map<String, String>) user.getAttributes().get("lotusCredentials");
InputStream inputStream = context.getEntityStream();
byte[] bytes = new byte[inputStream.available()];
inputStream.read(bytes);
String responseContent = new String(bytes);
String id = context.getUriInfo().getPathParameters().getFirst("id");
Object existingObject = null;
try {
existingObject = existingObjectDao.get(id, authParams);
} catch (Exception e) {
e.printStackTrace();
}
if (existingObject != null) {
ObjectMapper objectMapper = new ObjectMapper();
ObjectReader reader = objectMapper.readerForUpdating(existingObject );
JsonNode r = reader.readTree(responseContent);
responseContent = objectMapper.writer().writeValueAsString(r);
}
context.setEntityStream(new ByteArrayInputStream(responseContent.getBytes()));
}
}