private List<String> patternAsList(@Nullable String input) {
        if (input != null && input.contains(",")) {
            return Arrays.asList(input.split(","));
        } else {
            return Collections.singletonList(input);
        }
    }
Splits the input on ',' if non-null and a ',' is present.
Returns a singletonList of null if null
querydsl-sql-codegen/src/main/java/com/querydsl/sql/codegen/MetaDataExporter.java