class AbstractExpressionEvaluator implements ExpressionEvaluator {

    protected boolean isSimpleTypeNode(JsonNode jsonNode) {
        if (!jsonNode.isObject()) {
            return false;
        }
        ObjectNode objectNode = (ObjectNode) jsonNode;
        int numberOfFields = objectNode.size();
        return numberOfFields == 1 && objectNode.has(VALUE);
    }

}