001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.beans;
018
019import org.springframework.lang.Nullable;
020
021/**
022 * Interface representing an object whose value set can be merged with
023 * that of a parent object.
024 *
025 * @author Rob Harrop
026 * @since 2.0
027 * @see org.springframework.beans.factory.support.ManagedSet
028 * @see org.springframework.beans.factory.support.ManagedList
029 * @see org.springframework.beans.factory.support.ManagedMap
030 * @see org.springframework.beans.factory.support.ManagedProperties
031 */
032public interface Mergeable {
033
034        /**
035         * Is merging enabled for this particular instance?
036         */
037        boolean isMergeEnabled();
038
039        /**
040         * Merge the current value set with that of the supplied object.
041         * <p>The supplied object is considered the parent, and values in
042         * the callee's value set must override those of the supplied object.
043         * @param parent the object to merge with
044         * @return the result of the merge operation
045         * @throws IllegalArgumentException if the supplied parent is {@code null}
046         * @throws IllegalStateException if merging is not enabled for this instance
047         * (i.e. {@code mergeEnabled} equals {@code false}).
048         */
049        Object merge(@Nullable Object parent);
050
051}