How to populate formbean with ONLY updated values?

Question

Is there a way to populate the formbean with ONLY updated values in Java Struts?
Ex: Out of 50 fields displayed on GUI, If lets say user modifies 20 fields, I need to capture only those 20 fields into the form bean.
The reason i am looking for such function is to avoid the overhead of updating all the 50 fields into the database everytime even if one field is modified.

Answer 1

Normally, you update the entire record if one of the fields is changed. However, if you display more than one record, only those records have have changed should be updated. The reason you dont update all records is because if the performance hit on updating records that didn't change, among other things (see optimistic conurrency topic at http://msdn.microsoft.com/en-us/library/bb399373.aspx)
I don't think you should bother coding to only capture those fields that have changed in one record. It complicates your code and makes it difficult to read. Also, performance gain on not reading unchanged fields is offset by performance loss on the logic to manage such a task. Also, your update sql statement will be overly complicated and will have to be dynamically built rather than a single simple update sql statement that updates all fields.