Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.tang.util.walk;
020
021import org.apache.reef.tang.types.ClassNode;
022import org.apache.reef.tang.types.NamedParameterNode;
023import org.apache.reef.tang.types.Node;
024import org.apache.reef.tang.types.PackageNode;
025
026/**
027 * Generic interface to traverse nodes of the class hierarchy.
028 * Dispatches between ClassNode, PackageNode, and NamedParameterNode types.
029 * It is used e.g. in Walk.preorder()
030 */
031public abstract class AbstractClassHierarchyNodeVisitor implements NodeVisitor<Node> {
032
033  /**
034   * Manually dispatch between different types of Nodes and call a proper visit() method.
035   * Currently dispatches between ClassNode, PackageNode, and NamedParameterNode types.
036   *
037   * @param node TANG configuration node.
038   * @return true to proceed with the next node, false to cancel.
039   * @throws ClassCastException if Node is not one of ClassNode, PackageNode,
040   *                            or NamedParameterNode.
041   */
042  @Override
043  public boolean visit(final Node node) {
044    if (node instanceof ClassNode) {
045      return visit((ClassNode<?>) node);
046    } else if (node instanceof PackageNode) {
047      return visit((PackageNode) node);
048    } else if (node instanceof NamedParameterNode) {
049      return visit((NamedParameterNode<?>) node);
050    }
051    throw new ClassCastException(
052        "Node " + node.getClass() + " cannot be casted to one of the known subclasses."
053            + " Override this method to handle the case.");
054  }
055
056  /**
057   * Process current configuration node of ClassNode type.
058   *
059   * @param node Current configuration node.
060   * @return true to proceed with the next node, false to cancel.
061   */
062  public abstract boolean visit(ClassNode<?> node);
063
064  /**
065   * Process current configuration node of PackageNode type.
066   *
067   * @param node Current configuration node.
068   * @return true to proceed with the next node, false to cancel.
069   */
070  public abstract boolean visit(PackageNode node);
071
072  /**
073   * Process current configuration node of NamedParameterNode type.
074   *
075   * @param node Current configuration node.
076   * @return true to proceed with the next node, false to cancel.
077   */
078  public abstract boolean visit(NamedParameterNode<?> node);
079}