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package org.apache.cayenne.util;

import org.apache.cayenne.project.ProjectPath;

/**
 * A hierarchical visitor interface used for tree structures traversal.
 * 
 * @author Andrus Adamchik
 */
// TODO, andrus, 4/24/2006 - move to Cayenne core in 2.0
public interface HierarchicalTreeVisitor {

    /**
     * Invoked in the beginning of the element subtree traversal. Traversal is done in a
     * depth-first manner, so returning false from this method would suppress child
     * elements traversal.
     */
    boolean onStartNode(ProjectPath path);

    /**
     * Invoked at the end of the annotation tree traversal, which is done in a depth-first
     * manner.
     */
    void onFinishNode(ProjectPath path);

    /**
     * Returns an instance of the child visitor for a given project path and a type of
     * child. Returning null would result in skipping the particular child type.
     */
    HierarchicalTreeVisitor childVisitor(ProjectPath path, Class childType);
}
