I get a request in the format of string. I have to parse this string, get to know what type of request it is and populate different fields in objects of corresponding request class. There are around 6 request classes. These request classses have some fields in common but not all. I want to do parsing the string and getting required fields at only one place and I do not want to repeat this in every request class. how can I achive this? By using which design pattern?