Thanks for your quick response.
I investigate more and my ContextResolver is called.
The problem is now from XmlJAXBContextFinder, like https://jira.jboss.org/jira/browse/RESTEASY-229 but at line 37 : instead of
jaxb = findProvidedJAXBContext((Class<?>) type, mediaType);
if (jaxb != null)

{ cache.putIfAbsent((Class<?>) type, jaxb); result = jaxb; }

I put a return :
jaxb = findProvidedJAXBContext((Class<?>) type, mediaType);
if (jaxb != null)

{ cache.putIfAbsent((Class<?>) type, jaxb); return jaxb; }

Now it works.
Else my context with necessary classes is replaced next line by a context knowing one class.