- Author: [HuiFer](https://github.com/huifer)

- 源码阅读仓库: [SourceHot-spring-boot](https://github.com/SourceHot/spring-boot-read)

1. 创建配置文件`application.yml`

2. 全局搜索yml


3. 换成`properties`搜索


4. 我们以`yml`为例打上断点开始源码追踪

看到调用堆栈


- 一步一步回上去看如何调用具体方法的

- 配置文件监听器



protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {

RandomValuePropertySource.addToEnvironment(environment);

// 加载器加载信息

new Loader(environment, resourceLoader).load();

}

- 配置资源加载器

构造方法

Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {

// 环境配置

this.environment = environment;

// 占位符处理器

this.placeholdersResolver = new PropertySourcesPlaceholdersResolver(this.environment);

// 资源加载器

this.resourceLoader = (resourceLoader != null) ? resourceLoader : new DefaultResourceLoader();

// 配置信息加载器初始化

this.propertySourceLoaders = SpringFactoriesLoader.loadFactories(PropertySourceLoader.class,

getClass().getClassLoader());

}

- 熟悉的老朋友`this.propertySourceLoaders = SpringFactoriesLoader.loadFactories(PropertySourceLoader.class, getClass().getClassLoader())`， 看看**`spring.factories`**有什么

- 搜索目标: `org.springframework.boot.env.PropertySourceLoader`



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。


初始化完成，后续进行解析了

void load() {

FilteredPropertySource.apply(this.environment, DEFAULT_PROPERTIES, LOAD_FILTERED_PROPERTY,

(defaultProperties) -> {

this.profiles = new LinkedList<>();

this.processedProfiles = new LinkedList<>();

this.activatedProfiles = false;

this.loaded = new LinkedHashMap<>();

// 初始化配置文件

initializeProfiles();

while (!this.profiles.isEmpty()) {

Profile profile = this.profiles.poll();

if (isDefaultProfile(profile)) {

addProfileToEnvironment(profile.getName());

}

load(profile, this::getPositiveProfileFilter,

addToLoaded(MutablePropertySources::addLast, false));

this.processedProfiles.add(profile);

}

load(null, this::getNegativeProfileFilter, addToLoaded(MutablePropertySources::addFirst, true));

addLoadedPropertySources();

applyActiveProfiles(defaultProperties);

});

}

- 初始化`private Deque<Profile> profiles;` 属性

- 

- `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)`

private void load(Profile profile, DocumentFilterFactory filterFactory, DocumentConsumer consumer) {

getSearchLocations().forEach(

// 本地路径

(location) -> {

// 是不是文件夹

boolean isFolder = location.endsWith("/");

// 文件名,默认application

Set<String> names = isFolder ? getSearchNames() : NO_SEARCH_NAMES;

// 循环加载

names.forEach((name) -> {

load(location, name, profile, filterFactory, consumer);

});

});

}

- 资源路径可能性


该方法采用循环每个路径下面都去尝试一遍

- 中间过程省略，我们直接看最后的加载行为

- `org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#loadDocuments`

private List<Document> loadDocuments(PropertySourceLoader loader, String name, Resource resource)

throws IOException {

// 文档的缓存key

DocumentsCacheKey cacheKey = new DocumentsCacheKey(loader, resource);

// 文档信息

List<Document> documents = this.loadDocumentsCache.get(cacheKey);

if (documents == null) {

// 执行加载，将配置文件读取返回

List<PropertySource<?>> loaded = loader.load(name, resource);

// 数据转换

documents = asDocuments(loaded);

// 缓存设置

this.loadDocumentsCache.put(cacheKey, documents);

}

return documents;

}

此处的`loader.load()`调用具体的loader实现类进行执行方法

@Override

public List<PropertySource<?>> load(String name, Resource resource) throws IOException {

if (!ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", null)) {

throw new IllegalStateException(

"Attempted to load " + name + " but snakeyaml was not found on the classpath");

}

// 将资源转换成集合对象

List<Map<String, Object>> loaded = new OriginTrackedYamlLoader(resource).load();

if (loaded.isEmpty()) {

return Collections.emptyList();

}

List<PropertySource<?>> propertySources = new ArrayList<>(loaded.size());

for (int i = 0; i < loaded.size(); i++) {

String documentNumber = (loaded.size() != 1) ? " (document #" + i + ")" : "";

// 放入返回结果中

propertySources.add(new OriginTrackedMapPropertySource(name + documentNumber,

Collections.unmodifiableMap(loaded.get(i)), true));

}

return propertySources;

}


- `PropertiesPropertySourceLoader`解析同理不在次展开描述了

/**

private List<Document> asDocuments(List<PropertySource<?>> loaded) {

if (loaded == null) {

return Collections.emptyList();

}

return loaded.stream().map(

// 循环创建新对象

(propertySource) -> {

// 对象创建

Binder binder = new Binder(ConfigurationPropertySources.from(propertySource),

this.placeholdersResolver);

/**

return new Document(propertySource, binder.bind("spring.profiles", STRING_ARRAY).orElse(null),

getProfiles(binder, ACTIVE_PROFILES_PROPERTY),

getProfiles(binder, INCLUDE_PROFILES_PROPERTY));

}).collect(Collectors.toList());

}