When you submit the page, Visualforce will update the OwnerId field of your opportunity object a automatically for you. If you want to use that value elsewhere (e.g. in a save method), you can just reference the value directly:

Id newApproverId = a.OwnerId;
...


and you can query for the corresponding name (if you need that):

String newApproverName = [select Name from User where Id = :a.OwnerId].Name;
...


how to pass value from visual force page (InputField) to controller?
Does Java license allow other companies to create their own versions of Java language or just implement it accurately? Same question about JVM.

I heard about Sun suing Microsoft for changing their .NET version of Java implementation and Java for Google Android, but I just can't grasp the whole concept as a totality.
