001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.configuration2.beanutils; 018 019import java.util.ArrayList; 020import java.util.Arrays; 021import java.util.Collection; 022import java.util.Collections; 023import java.util.HashMap; 024import java.util.Map; 025import java.util.Objects; 026import java.util.function.Function; 027 028/** 029 * <p> 030 * A special implementation of the {@code BeanDeclaration} interface which allows combining multiple 031 * {@code BeanDeclaration} objects. 032 * </p> 033 * <p> 034 * An instance of this class can be used if a bean is defined using multiple sources. For instance, there can be one 035 * definition with default values and one with actual values; if actual values are provided, they are used; otherwise, 036 * the default values apply. 037 * </p> 038 * <p> 039 * When constructing an instance an arbitrary number of child {@code BeanDeclaration} objects can be specified. The 040 * implementations of the {@code BeanDeclaration} methods implement a logical combination of the data returned by these 041 * child declarations. The order in which child declarations are added is relevant; first entries take precedence over 042 * later ones. The comments of the single methods explain in which way a combination of the child declarations is built. 043 * </p> 044 * 045 * @since 2.0 046 */ 047public class CombinedBeanDeclaration implements BeanDeclaration { 048 049 /** A list with the child declarations. */ 050 private final ArrayList<BeanDeclaration> childDeclarations; 051 052 /** 053 * Constructs a new instance of {@code CombinedBeanDeclaration} and initializes it with the given child declarations. 054 * 055 * @param decl the child declarations 056 * @throws NullPointerException if the array with child declarations is <b>null</b> 057 */ 058 public CombinedBeanDeclaration(final BeanDeclaration... decl) { 059 childDeclarations = new ArrayList<>(Arrays.asList(decl)); 060 } 061 062 /** 063 * {@inheritDoc} This implementation iterates over the list of child declarations and asks them for a bean factory name. 064 * The first non-<b>null</b> value is returned. If none of the child declarations have a defined bean factory name, 065 * result is <b>null</b>. 066 */ 067 @Override 068 public String getBeanFactoryName() { 069 return findFirst(BeanDeclaration::getBeanFactoryName); 070 } 071 072 private <T> T findFirst(final Function<? super BeanDeclaration, ? extends T> mapper) { 073 return childDeclarations.stream().map(mapper).filter(Objects::nonNull).findFirst().orElse(null); 074 } 075 076 /** 077 * {@inheritDoc} This implementation iterates over the list of child declarations and asks them for a bean factory 078 * parameter. The first non-<b>null</b> value is returned. If none of the child declarations have a defined bean factory 079 * parameter, result is <b>null</b>. 080 */ 081 @Override 082 public Object getBeanFactoryParameter() { 083 return findFirst(BeanDeclaration::getBeanFactoryParameter); 084 } 085 086 /** 087 * {@inheritDoc} This implementation iterates over the list of child declarations and asks them for the bean class name. 088 * The first non-<b>null</b> value is returned. If none of the child declarations have a defined bean class, result is 089 * <b>null</b>. 090 */ 091 @Override 092 public String getBeanClassName() { 093 return findFirst(BeanDeclaration::getBeanClassName); 094 } 095 096 /** 097 * {@inheritDoc} This implementation creates a union of the properties returned by all child declarations. If a property 098 * is defined in multiple child declarations, the declaration that comes before in the list of children takes 099 * precedence. 100 */ 101 @Override 102 public Map<String, Object> getBeanProperties() { 103 return get(BeanDeclaration::getBeanProperties); 104 } 105 106 private Map<String, Object> get(final Function<? super BeanDeclaration, ? extends Map<String, Object>> mapper) { 107 @SuppressWarnings("unchecked") 108 final ArrayList<BeanDeclaration> temp = (ArrayList<BeanDeclaration>) childDeclarations.clone(); 109 Collections.reverse(temp); 110 return temp.stream().map(mapper).filter(Objects::nonNull).collect(HashMap::new, HashMap::putAll, HashMap::putAll); 111 } 112 113 /** 114 * {@inheritDoc} This implementation creates a union of the nested bean declarations returned by all child declarations. 115 * If a complex property is defined in multiple child declarations, the declaration that comes before in the list of 116 * children takes precedence. 117 */ 118 @Override 119 public Map<String, Object> getNestedBeanDeclarations() { 120 return get(BeanDeclaration::getNestedBeanDeclarations); 121 } 122 123 /** 124 * {@inheritDoc} This implementation iterates over the list of child declarations and asks them for constructor 125 * arguments. The first non-<b>null</b> and non empty collection is returned. If none of the child declarations provide 126 * constructor arguments, result is an empty collection. 127 */ 128 @Override 129 public Collection<ConstructorArg> getConstructorArgs() { 130 for (final BeanDeclaration d : childDeclarations) { 131 final Collection<ConstructorArg> args = d.getConstructorArgs(); 132 if (args != null && !args.isEmpty()) { 133 return args; 134 } 135 } 136 return Collections.emptyList(); 137 } 138}