public boolean isReadable(Class<?> type, //
                              Type genericType, //
                              Annotation[] annotations, //
                              MediaType mediaType) {

        if (!hasMatchingMediaType(mediaType)) {
            return false;
        }

        if (!isAssignableFrom(type, DEFAULT_UNREADABLES))
            return false;

        return isValidType(type, annotations);
    }
Method that JAX-RS container calls to try to check whether values of
given type (and media type) can be deserialized by this provider.
src/main/java/com/alibaba/fastjson/support/jaxrs/FastJsonProvider.java