         _headers = null;
         _params = null;
         _fields = null;
-        _contentType = "application/json";
-        _responseContentType = "application/json";
+        _contentType = DEFAULT_CONTENT_TYPE;
+        _responseContentType = DEFAULT_RESPONSE_CONTENT_TYPE;
         _accessTokenKey = null;
         _accessTokenValue = null;
         accessTokenSpecified = false;

        resultCallback = null;
        progressCallback = null;
        errorCallback = null;
        headerCallbacks = {};

        stubValue = null;

    //  contentType
    //------------------------------------

    private var _contentType:String = DEFAULT_CONTENT_TYPE;

    public function contentType(value:String):RestClient
    {
