001/* 002 * Copyright 2012-2018 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 * http://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.boot.context.properties.source; 018 019import java.util.function.Predicate; 020 021import org.springframework.boot.origin.OriginTrackedValue; 022 023/** 024 * A source of {@link ConfigurationProperty ConfigurationProperties}. 025 * 026 * @author Phillip Webb 027 * @author Madhura Bhave 028 * @since 2.0.0 029 * @see ConfigurationPropertyName 030 * @see OriginTrackedValue 031 * @see #getConfigurationProperty(ConfigurationPropertyName) 032 */ 033@FunctionalInterface 034public interface ConfigurationPropertySource { 035 036 /** 037 * Return a single {@link ConfigurationProperty} from the source or {@code null} if no 038 * property can be found. 039 * @param name the name of the property (must not be {@code null}) 040 * @return the associated object or {@code null}. 041 */ 042 ConfigurationProperty getConfigurationProperty(ConfigurationPropertyName name); 043 044 /** 045 * Returns if the source contains any descendants of the specified name. May return 046 * {@link ConfigurationPropertyState#PRESENT} or 047 * {@link ConfigurationPropertyState#ABSENT} if an answer can be determined or 048 * {@link ConfigurationPropertyState#UNKNOWN} if it's not possible to determine a 049 * definitive answer. 050 * @param name the name to check 051 * @return if the source contains any descendants 052 */ 053 default ConfigurationPropertyState containsDescendantOf( 054 ConfigurationPropertyName name) { 055 return ConfigurationPropertyState.UNKNOWN; 056 } 057 058 /** 059 * Return a filtered variant of this source, containing only names that match the 060 * given {@link Predicate}. 061 * @param filter the filter to match 062 * @return a filtered {@link ConfigurationPropertySource} instance 063 */ 064 default ConfigurationPropertySource filter( 065 Predicate<ConfigurationPropertyName> filter) { 066 return new FilteredConfigurationPropertiesSource(this, filter); 067 } 068 069 /** 070 * Return a variant of this source that supports name aliases. 071 * @param aliases a function that returns a stream of aliases for any given name 072 * @return a {@link ConfigurationPropertySource} instance supporting name aliases 073 */ 074 default ConfigurationPropertySource withAliases( 075 ConfigurationPropertyNameAliases aliases) { 076 return new AliasedConfigurationPropertySource(this, aliases); 077 } 078 079 /** 080 * Return the underlying source that is actually providing the properties. 081 * @return the underlying property source or {@code null}. 082 */ 083 default Object getUnderlyingSource() { 084 return null; 085 } 086 087}