class StringComplexFieldActions implements AtlasFieldAction {

    @AtlasActionProcessor
    public static String append(Append append, String input) {
        if (append == null) {
            throw new IllegalArgumentException("Append must be specified with a string");
        }
        String string = append.getString();
        if (input == null && string == null) {
            return null;
        }
        if (string == null) {
            return input.toString();
        }
        return input == null ? string : input.toString().concat(string);
    }

}