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# Spring Boot application 文件加载
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- Author: [HuiFer](https://github.com/huifer)
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- 源码阅读仓库: [SourceHot-spring-boot](https://github.com/SourceHot/spring-boot-read)
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## 如何找到这个加载的过程
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1. 创建配置文件`application.yml`
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2. 全局搜索 yml
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3. 换成`properties`搜索
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4. 我们以`yml`为例打上断点开始源码追踪
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看到调用堆栈
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- 一步一步回上去看如何调用具体方法的
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## ConfigFileApplicationListener
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- 配置文件监听器
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### 调用过程
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`org.springframework.boot.context.config.ConfigFileApplicationListener#addPropertySources`
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```java
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protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
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RandomValuePropertySource.addToEnvironment(environment);
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// 加载器加载信息
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new Loader(environment, resourceLoader).load();
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}
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```
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### Loader
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- 配置资源加载器
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构造方法
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```java
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Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
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// 环境配置
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this.environment = environment;
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// 占位符处理器
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this.placeholdersResolver = new PropertySourcesPlaceholdersResolver(this.environment);
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// 资源加载器
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this.resourceLoader = (resourceLoader != null) ? resourceLoader : new DefaultResourceLoader();
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// 配置信息加载器初始化
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this.propertySourceLoaders = SpringFactoriesLoader.loadFactories(PropertySourceLoader.class,
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getClass().getClassLoader());
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}
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```
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- 熟悉的老朋友`this.propertySourceLoaders = SpringFactoriesLoader.loadFactories(PropertySourceLoader.class, getClass().getClassLoader())`， 看看**`spring.factories`**有什么
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- 搜索目标: `org.springframework.boot.env.PropertySourceLoader`
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观察发现里面有一个`YamlPropertySourceLoader`和我们之前找 yml 字符串的时候找到的类是一样的。说明搜索方式没有什么问题。
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初始化完成，后续进行解析了
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### load 方法
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```java
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void load() {
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FilteredPropertySource.apply(this.environment, DEFAULT_PROPERTIES, LOAD_FILTERED_PROPERTY,
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(defaultProperties) -> {
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this.profiles = new LinkedList<>();
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this.processedProfiles = new LinkedList<>();
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this.activatedProfiles = false;
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this.loaded = new LinkedHashMap<>();
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// 初始化配置文件
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initializeProfiles();
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while (!this.profiles.isEmpty()) {
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Profile profile = this.profiles.poll();
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if (isDefaultProfile(profile)) {
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addProfileToEnvironment(profile.getName());
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}
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load(profile, this::getPositiveProfileFilter,
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addToLoaded(MutablePropertySources::addLast, false));
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this.processedProfiles.add(profile);
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}
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load(null, this::getNegativeProfileFilter, addToLoaded(MutablePropertySources::addFirst, true));
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addLoadedPropertySources();
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applyActiveProfiles(defaultProperties);
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});
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}
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```
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### initializeProfiles
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- 初始化`private Deque<Profile> profiles;` 属性
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- 
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### load
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- `org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#load(org.springframework.boot.context.config.ConfigFileApplicationListener.Profile, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentFilterFactory, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentConsumer)`
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```java
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private void load(Profile profile, DocumentFilterFactory filterFactory, DocumentConsumer consumer) {
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getSearchLocations().forEach(
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// 本地路径
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(location) -> {
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// 是不是文件夹
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boolean isFolder = location.endsWith("/");
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// 文件名,默认application
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Set<String> names = isFolder ? getSearchNames() : NO_SEARCH_NAMES;
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// 循环加载
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names.forEach((name) -> {
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load(location, name, profile, filterFactory, consumer);
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});
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});
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}
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```
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- 资源路径可能性
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该方法采用循环每个路径下面都去尝试一遍
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- 中间过程省略，我们直接看最后的加载行为
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- `org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#loadDocuments`
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```java
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private List<Document> loadDocuments(PropertySourceLoader loader, String name, Resource resource)
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throws IOException {
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// 文档的缓存key
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DocumentsCacheKey cacheKey = new DocumentsCacheKey(loader, resource);
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// 文档信息
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List<Document> documents = this.loadDocumentsCache.get(cacheKey);
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if (documents == null) {
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// 执行加载，将配置文件读取返回
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List<PropertySource<?>> loaded = loader.load(name, resource);
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// 数据转换
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documents = asDocuments(loaded);
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// 缓存设置
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this.loadDocumentsCache.put(cacheKey, documents);
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}
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return documents;
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}
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```
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此处的`loader.load()`调用具体的 loader 实现类进行执行方法
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### yml 解析
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```java
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@Override
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public List<PropertySource<?>> load(String name, Resource resource) throws IOException {
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if (!ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", null)) {
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throw new IllegalStateException(
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"Attempted to load " + name + " but snakeyaml was not found on the classpath");
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}
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// 将资源转换成集合对象
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List<Map<String, Object>> loaded = new OriginTrackedYamlLoader(resource).load();
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if (loaded.isEmpty()) {
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return Collections.emptyList();
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}
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List<PropertySource<?>> propertySources = new ArrayList<>(loaded.size());
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for (int i = 0; i < loaded.size(); i++) {
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String documentNumber = (loaded.size() != 1) ? " (document #" + i + ")" : "";
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// 放入返回结果中
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propertySources.add(new OriginTrackedMapPropertySource(name + documentNumber,
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Collections.unmodifiableMap(loaded.get(i)), true));
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}
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return propertySources;
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}
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```
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- `PropertiesPropertySourceLoader`解析同理不在次展开描述了
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### asDocuments
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```java
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/**
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* 将 {@link PropertySource} 转换成 {@link Document}
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* @param loaded
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* @return
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*/
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private List<Document> asDocuments(List<PropertySource<?>> loaded) {
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if (loaded == null) {
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return Collections.emptyList();
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}
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return loaded.stream().map(
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// 循环创建新对象
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(propertySource) -> {
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// 对象创建
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Binder binder = new Binder(ConfigurationPropertySources.from(propertySource),
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this.placeholdersResolver);
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/**
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* 通过 {@link Binder} 将数据进行绑定，创建 {@link Document}进行返回
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*/
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return new Document(propertySource, binder.bind("spring.profiles", STRING_ARRAY).orElse(null),
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getProfiles(binder, ACTIVE_PROFILES_PROPERTY),
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getProfiles(binder, INCLUDE_PROFILES_PROPERTY));
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}).collect(Collectors.toList());
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}
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```
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---
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