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}