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  package org.apache.cayenne.graph;
  
  import org.apache.cayenne.event.CayenneEvent;
  
  /**
   * An event indicating a change in the object graph. A change is expressed as a
   * GraphDiff, so the easiest way to process the event is the following:
   * 
   * <pre>
   *    GraphChangeHandler handler = ..;
   *    event.getDiff().apply(handler);
   * </pre>
   * 
   * @since 1.2
   */
  public class GraphEvent extends CayenneEvent {
  
  	private static final long serialVersionUID = -8954343713674462675L;
  	
  	protected GraphDiff diff;
  
  	public GraphEvent(Object source, GraphDiff diff) {
  		this(source, source, diff);
  	}
  
  	public GraphEvent(Object source, Object postedBy, GraphDiff diff) {
  		super(source, postedBy, null);
  		this.diff = diff;
  	}
  
  	public GraphDiff getDiff() {
  		return diff;
  	}
  }
  