Description

General goal

Be able to use event to cancel actions.

Use case

• cancel document saving
• cancel script execution
  • for security reasons (e.g. nested scripts)
  • because of errors in initialization
• ...

Proposal

interface CancelableEvent extends Event
{
  boolean isCanceled();

  void cancel();

  void cancel(String reason);

  String getReason();
}

class AbstractCancelableEvent implements CancelableEvent
{
  private boolean canceled = false;

  private String reason;

  public boolean isCanceled()
  {
    return this.canceled;
  }

  public void cancel()
  {
    this.cancel = true;
  }

  public void cancel(String reason)
  {
    this.reason = reason;
  }

  public String getReason()
  {
    retrun this.reason;
  }
}

A cancelable event implements CancelableEvent and any listener of this event can cancel the event by calling #cancel() method. Then the sender of the event uses #isCanceled() to know it has to cancel the action.