Basic HTML version of Foils prepared May 19 99

Foil 29 Updating a Constrained Property Value

From Javabeans Basic Information Track Computational Science Course CPS616 -- Spring Semester 1999. by Geoffrey Fox, Nancy McCracken, Wojtek Furmanski
1 To update a constrained property value:
  • notify all vetoable listeners that a change is about to occur, using the fireVetoableChange method of the VetoableChangeSupport class, which passes the proposed update to the vetoable listeners.
  • If a listener wants to veto the update, it will throw a PropertyVetoException from its VetoableChange method.
  • If none of the vetoable listeners has thrown a PropertyVetoException, then proceed with the update.
  • Notify all property listeners that a change has occurred.
2 If more than one bean wants to veto property changes, then it may be quite complicated to work out when to keep the old value or move to the new value.
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