001/* 002 * Copyright 2002-2019 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.factory.config; 018 019import java.util.LinkedHashMap; 020import java.util.Map; 021 022import org.springframework.beans.factory.FactoryBean; 023import org.springframework.beans.factory.InitializingBean; 024import org.springframework.lang.Nullable; 025 026/** 027 * Factory for a {@code Map} that reads from a YAML source, preserving the 028 * YAML-declared value types and their structure. 029 * 030 * <p>YAML is a nice human-readable format for configuration, and it has some 031 * useful hierarchical properties. It's more or less a superset of JSON, so it 032 * has a lot of similar features. 033 * 034 * <p>If multiple resources are provided the later ones will override entries in 035 * the earlier ones hierarchically; that is, all entries with the same nested key 036 * of type {@code Map} at any depth are merged. For example: 037 * 038 * <pre class="code"> 039 * foo: 040 * bar: 041 * one: two 042 * three: four 043 * </pre> 044 * 045 * plus (later in the list) 046 * 047 * <pre class="code"> 048 * foo: 049 * bar: 050 * one: 2 051 * five: six 052 * </pre> 053 * 054 * results in an effective input of 055 * 056 * <pre class="code"> 057 * foo: 058 * bar: 059 * one: 2 060 * three: four 061 * five: six 062 * </pre> 063 * 064 * Note that the value of "foo" in the first document is not simply replaced 065 * with the value in the second, but its nested values are merged. 066 * 067 * <p>Requires SnakeYAML 1.18 or higher, as of Spring Framework 5.0.6. 068 * 069 * @author Dave Syer 070 * @author Juergen Hoeller 071 * @since 4.1 072 */ 073public class YamlMapFactoryBean extends YamlProcessor implements FactoryBean<Map<String, Object>>, InitializingBean { 074 075 private boolean singleton = true; 076 077 @Nullable 078 private Map<String, Object> map; 079 080 081 /** 082 * Set if a singleton should be created, or a new object on each request 083 {@code true} (a singleton). 084 */ 085 public void setSingleton(boolean singleton) { 086 this.singleton = singleton; 087 } 088 089 @Override 090 public boolean isSingleton() { 091 return this.singleton; 092 } 093 094 @Override 095 public void afterPropertiesSet() { 096 if (isSingleton()) { 097 this.map = createMap(); 098 } 099 } 100 101 @Override 102 @Nullable 103 public Map<String, Object> getObject() { 104 return (this.map != null ? this.map : createMap()); 105 } 106 107 @Override 108 public Class<?> getObjectType() { 109 return Map.class; 110 } 111 112 113 /** 114 * Template method that subclasses may override to construct the object 115 * returned by this factory. 116 * <p>Invoked lazily the first time {@link #getObject()} is invoked in 117 * case of a shared singleton; else, on each {@link #getObject()} call. 118 * <p>The default implementation returns the merged {@code Map} instance. 119 * @return the object returned by this factory 120 * @see #process(MatchCallback) 121 */ 122 protected Map<String, Object> createMap() { 123 Map<String, Object> result = new LinkedHashMap<>(); 124 process((properties, map) -> merge(result, map)); 125 return result; 126 } 127 128 @SuppressWarnings({"rawtypes", "unchecked"}) 129 private void merge(Map<String, Object> output, Map<String, Object> map) { 130 map.forEach((key, value) -> { 131 Object existing = output.get(key); 132 if (value instanceof Map && existing instanceof Map) { 133 // Inner cast required by Eclipse IDE. 134 Map<String, Object> result = new LinkedHashMap<>((Map<String, Object>) existing); 135 merge(result, (Map) value); 136 output.put(key, result); 137 } 138 else { 139 output.put(key, value); 140 } 141 }); 142 } 143 144}