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.implementation.Constructor;
022import org.apache.reef.tang.implementation.InjectionPlan;
023import org.apache.reef.tang.implementation.Subplan;
024import org.apache.reef.tang.implementation.java.JavaInstance;
025
026/**
027 * Generic interface to traverse nodes of the injection plan.
028 * Dispatches between Constructor, Subplan, RequiredSingleton, and JavaInstance types.
029 * It is used e.g. in Walk.preorder()
030 */
031public abstract class AbstractInjectionPlanNodeVisitor implements NodeVisitor<InjectionPlan<?>> {
032
033  /**
034   * Manually dispatch between different types of injection plan objects and call proper
035   * visit() method. Currently dispatches between Constructor, Subplan, RequiredSingleton,
036   * and JavaInstance types.
037   *
038   * @param node TANG injection plan node.
039   * @return true to proceed with the next node, false to cancel.
040   * @throws ClassCastException if argument is not one of Constructor, Subplan,
041   *                            RequiredSingleton, or JavaInstance.
042   */
043  @Override
044  public boolean visit(final InjectionPlan<?> node) {
045    if (node instanceof Constructor<?>) {
046      return visit((Constructor<?>) node);
047    } else if (node instanceof Subplan<?>) {
048      return visit((Subplan<?>) node);
049    } else if (node instanceof JavaInstance<?>) {
050      return visit((JavaInstance<?>) node);
051    }
052    throw new ClassCastException(
053        "Node " + node.getClass() + " cannot be casted to one of the known subclasses."
054            + " Override this method to handle the case.");
055  }
056
057  /**
058   * Process current injection plan node of Constructor type.
059   *
060   * @param node Current injection plan node.
061   * @return true to proceed with the next node, false to cancel.
062   */
063  public abstract boolean visit(Constructor<?> node);
064
065  /**
066   * Process current injection plan node of JavaInstance type.
067   *
068   * @param node Current injection plan node.
069   * @return true to proceed with the next node, false to cancel.
070   */
071  public abstract boolean visit(JavaInstance<?> node);
072
073  /**
074   * Process current injection plan node of Subplan type.
075   *
076   * @param node Current injection plan node.
077   * @return true to proceed with the next node, false to cancel.
078   */
079  public abstract boolean visit(Subplan<?> node);
080}