The concept of ValueObject

[Sanz Vai]

What exactly is a valueobject?
Isn't everything in Java passed by reference???

[Ajith Kallambella]

Yes, but what happens in a typical J2EE application where the web tier and the app tier are separate JVM instances? Do you know how objects are passed between JVMs? Think about it

[Sanz Vai]

I know the objects are serialized while passing to a diff JVM. Only a copy of the object is passed? But in any case, what's SO special about these VOs? A POJO is no different than VO, right?

[Ajith Kallambella]

Yes you are correct. Typical implementation of a value object is a POJO. However that does not preclude someone from implementing other forms of value objects. For instance, you can use an attribute hashmap pattern as a value object, or an XML DOM tree as a value object.