gobblin.util.DecoratorUtils.java Source code

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Here is the source code for gobblin.util.DecoratorUtils.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package gobblin.util;

import java.util.List;

import com.google.common.collect.Lists;

/**
 * Utilities for classes implementing the decorator interface.
 */
public class DecoratorUtils {

    /**
     * Resolves the truly underlying object in a possible chain of {@link gobblin.util.Decorator}.
     *
     * @param obj object to resolve.
     * @return the true non-decorator underlying object.
     */
    public static Object resolveUnderlyingObject(Object obj) {
        while (obj instanceof Decorator) {
            obj = ((Decorator) obj).getDecoratedObject();
        }
        return obj;
    }

    /**
     * Finds the decorator lineage of the given object.
     *
     * <p>
     * If object is not a {@link gobblin.util.Decorator}, this method will return a singleton list with just the object.
     * If object is a {@link gobblin.util.Decorator}, it will return a list of the underlying object followed by the
     * decorator lineage up to the input decorator object.
     * </p>
     *
     * @param obj an object.
     * @return List of the non-decorator underlying object and all decorators on top of it,
     *  starting with underlying object and ending with the input object itself (inclusive).
     */
    public static List<Object> getDecoratorLineage(Object obj) {
        List<Object> lineage = Lists.newArrayList(obj);
        Object currentObject = obj;
        while (currentObject instanceof Decorator) {
            currentObject = ((Decorator) currentObject).getDecoratedObject();
            lineage.add(currentObject);
        }

        return Lists.reverse(lineage);
    }
}