/*
 * Copyright 2012-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
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package org.springframework.boot.context.properties.source;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.function.Function;

import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.MutablePropertySources;
import org.springframework.core.env.PropertySource;
import org.springframework.core.env.PropertySource.StubPropertySource;
import org.springframework.util.Assert;
import org.springframework.util.ConcurrentReferenceHashMap;
import org.springframework.util.ConcurrentReferenceHashMap.ReferenceType;

Adapter to convert Spring's MutablePropertySources to ConfigurationPropertySources.
Author:Phillip Webb
/** * Adapter to convert Spring's {@link MutablePropertySources} to * {@link ConfigurationPropertySource ConfigurationPropertySources}. * * @author Phillip Webb */
class SpringConfigurationPropertySources implements Iterable<ConfigurationPropertySource> { private final Iterable<PropertySource<?>> sources; private final Map<PropertySource<?>, ConfigurationPropertySource> cache = new ConcurrentReferenceHashMap<>(16, ReferenceType.SOFT); SpringConfigurationPropertySources(Iterable<PropertySource<?>> sources) { Assert.notNull(sources, "Sources must not be null"); this.sources = sources; } @Override public Iterator<ConfigurationPropertySource> iterator() { return new SourcesIterator(this.sources.iterator(), this::adapt); } private ConfigurationPropertySource adapt(PropertySource<?> source) { ConfigurationPropertySource result = this.cache.get(source); // Most PropertySources test equality only using the source name, so we need to // check the actual source hasn't also changed. if (result != null && result.getUnderlyingSource() == source) { return result; } result = SpringConfigurationPropertySource.from(source); this.cache.put(source, result); return result; } private static class SourcesIterator implements Iterator<ConfigurationPropertySource> { private final Deque<Iterator<PropertySource<?>>> iterators; private ConfigurationPropertySource next; private final Function<PropertySource<?>, ConfigurationPropertySource> adapter; SourcesIterator(Iterator<PropertySource<?>> iterator, Function<PropertySource<?>, ConfigurationPropertySource> adapter) { this.iterators = new ArrayDeque<>(4); this.iterators.push(iterator); this.adapter = adapter; } @Override public boolean hasNext() { return fetchNext() != null; } @Override public ConfigurationPropertySource next() { ConfigurationPropertySource next = fetchNext(); if (next == null) { throw new NoSuchElementException(); } this.next = null; return next; } private ConfigurationPropertySource fetchNext() { if (this.next == null) { if (this.iterators.isEmpty()) { return null; } if (!this.iterators.peek().hasNext()) { this.iterators.pop(); return fetchNext(); } PropertySource<?> candidate = this.iterators.peek().next(); if (candidate.getSource() instanceof ConfigurableEnvironment) { push((ConfigurableEnvironment) candidate.getSource()); return fetchNext(); } if (isIgnored(candidate)) { return fetchNext(); } this.next = this.adapter.apply(candidate); } return this.next; } private void push(ConfigurableEnvironment environment) { this.iterators.push(environment.getPropertySources().iterator()); } private boolean isIgnored(PropertySource<?> candidate) { return (candidate instanceof StubPropertySource || candidate instanceof ConfigurationPropertySourcesPropertySource); } } }