28.7 Using State Management for Middle-Tier Savepoints

In the database server you are likely familiar with the savepoint feature that allows a developer to rollback to a certain point within a transaction instead of rolling back the entire transaction. An application module offers the same feature but implemented in the middle tier. There are three methods in oracle.jbo.ApplicationModule interface that allow you to take advantage of this feature. The methods are:

public String passivateStateForUndo(String id,byte[] clientData,int flags)
public byte[] activateStateForUndo(String id,int flags)
public boolean isValidIdForUndo(String id)

You can use these methods to create a stack of named snapshots and restore the pending transaction state from them by name. Keep in mind that those snapshots do not survive past duration of transaction (i.e. events of commit or rollback). This feature could be used to develop complex capabilities of the application, such as the ability to undo and redo changes. Another ambitious goal that could exploit this functionality would be functionality to make the browser back and forward buttons behave in an application-specific way. Otherwise, simple uses of these methods can come quite in handy.