private String normalize(String str) {
        if (lowerCase && str != null) {
            return str.toLowerCase();
        } else {
            return str;
        }
    }
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