code: public static Expression decodeJson(String jsonString) {
          try {
              JsonObject jsonObject = CouchbaseAsyncBucket.JSON_OBJECT_TRANSCODER.stringToJsonObject(jsonString);
              return decodeJson(jsonObject);
          } catch (Exception e) {
              throw new IllegalArgumentException("String is not representing JSON object: " + jsonString);
          }
      }
docs: The returned Expression unmarshals the JSON-encoded string
  into a N1QL value. The empty string results in MISSING.
  
  The string must represent JSON object marshalled into a JSON String,
  eg. "{\"test\": true}" (excluding surrounding quotes).