Detect if a Java-object has been modified?

Question

Consider that I’ve got a standard Java bean: i.e. it contains members that are String, List, HashMap, etc.

My question is: what’s the easiest way to detect if an instance of such an object has been modified from say a previous/original state?

The reason I want to know this is so I determine whether I should update the object in the DB, or not, in the case where either: (i) no changes were made, or (ii) changes were made but then reversed.

I’ve been thinking about comparison of hashCode, or byte[], but doesn’t seem to work. Any ideas?

Answer 1

Yes, it can be done, and it has been done... it's called hibernate. Just use that and don't "reinvent the wheel"

Answer 2

if you have setters, notify a list of listeners in this setters if a new value is set.

Answer 3

The same problem had hibernate developers, and they've dealt with it by creating proxies for returned entities. The proxy registers each setter call and so determines if entity has changed.