springboot(三)——application.properties和application.yml是何时解析的

实现一个简单的自定义监听器

第一步 :定义一个event，继承ApplicationEvent

public class CustomerApplicationEvent extends ApplicationEvent {
    public CustomerApplicationEvent(Object source) {
        super(source);
        System.out.println("CustomerApplicationEvent constructor...");
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第二步 :定义一个listener

@Component
public class CustomerApplicationListener implements ApplicationListener<CustomerApplicationEvent> {
    @Override
    public void onApplicationEvent(CustomerApplicationEvent customerApplicationEvent) {
        System.out.println("customerApplicationEvent:"+customerApplicationEvent.getClass().getName());
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第三步 :注册监听器

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(Application.class, args);
        // 注册 CustomerApplicationListener 事件监听器
        context.addApplicationListener(new CustomerApplicationListener());
        // 发布 CustomerApplicationEvent 事件
        context.publishEvent(new CustomerApplicationEvent(new Object()));
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启动项目后，会发现控制台输出了：

CustomerApplicationEvent constructor...
customerApplicationEvent:com.stone.zplxjj.event.CustomerApplicationEvent
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springboot自带的事件

ApplicationStartingEvent：应用启动事件，在调用 SpringApplication.run() 方法之前，可以从中获取到 SpringApplication 对象，进行一些启动前设置。

ApplicationEnvironmentPreparedEvent：Environment准备完成事件，此时可以从中获取到 Environment 对象并对其中的配置项进行查看或者修改 。

ApplicationPreparedEvent：ApplicationContext准备完成事件，接下来 Spring 就能够向容器中加载 Bean 了。

ApplicationReadyEvent：应用准备完成事件，预示着应用可以接收和处理请求了。

ApplicationFailedEvent：应用启动失败事件，可以从中捕获到启动失败的异常信息进行相应处理，例如：添加虚拟机对应的钩子进行资源的回收与释放。

读取配置代码入口：ApplicationEnvironmentPreparedEvent和ConfigFileApplicationListener

加载配置文件需要用到ConfigFileApplicationListener，其代码如下：

	@Override
	public void onApplicationEvent(ApplicationEvent event) {
		if (event instanceof ApplicationEnvironmentPreparedEvent) {
			onApplicationEnvironmentPreparedEvent(
					(ApplicationEnvironmentPreparedEvent) event);
		if (event instanceof ApplicationPreparedEvent) {
			onApplicationPreparedEvent(event);
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进入方法：onApplicationEnvironmentPreparedEvent

	private void onApplicationEnvironmentPreparedEvent(
			ApplicationEnvironmentPreparedEvent event) {
		List<EnvironmentPostProcessor> postProcessors = loadPostProcessors();
		postProcessors.add(this);
		AnnotationAwareOrderComparator.sort(postProcessors);
		for (EnvironmentPostProcessor postProcessor : postProcessors) {
			postProcessor.postProcessEnvironment(event.getEnvironment(),
					event.getSpringApplication());
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进入postProcessor.postProcessEnvironment：

  //类：ConfigFileApplicationListener
	@Override
	public void postProcessEnvironment(ConfigurableEnvironment environment,
			SpringApplication application) {
		addPropertySources(environment, application.getResourceLoader());
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进入addPropertySources

	protected void addPropertySources(ConfigurableEnvironment environment,
			ResourceLoader resourceLoader) {
        //将随机方法放入到PropertySources中
		RandomValuePropertySource.addToEnvironment(environment);
        //load加载
		new Loader(environment, resourceLoader).load();
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进入load方法：

		public void load() {
			this.profiles = new LinkedList<>();
			this.processedProfiles = new LinkedList<>();
			this.activatedProfiles = false;
			this.loaded = new LinkedHashMap<>();
			initializeProfiles();
			while (!this.profiles.isEmpty()) {
				Profile profile = this.profiles.poll();
				if (profile != null && !profile.isDefaultProfile()) {
					addProfileToEnvironment(profile.getName());
				load(profile, this::getPositiveProfileFilter,
						addToLoaded(MutablePropertySources::addLast, false));
				this.processedProfiles.add(profile);
			resetEnvironmentProfiles(this.processedProfiles);
			load(null, this::getNegativeProfileFilter,
					addToLoaded(MutablePropertySources::addFirst, true));
			addLoadedPropertySources();
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进入字方法load

    private void load(Profile profile, DocumentFilterFactory filterFactory,
				DocumentConsumer consumer) {
			getSearchLocations().forEach((location) -> {
				boolean isFolder = location.endsWith("/");
				Set<String> names = isFolder ? getSearchNames() : NO_SEARCH_NAMES;
				names.forEach(
						(name) -> load(location, name, profile, filterFactory, consumer));
getSearchLocations():首先看CONFIG_LOCATION_PROPERTY，是否存在配置，无则走默认配置路径DEFAULT_SEARCH_LOCATIONS
	 * The "config location" property name.
	public static final String CONFIG_LOCATION_PROPERTY = "spring.config.location";
	// Note the order is from least to most specific (last one wins)
	private static final String DEFAULT_SEARCH_LOCATIONS = "classpath:/,classpath:/config/,file:./,file:./config/";
getSearchNames():首先看CONFIG_NAME_PROPERTY(spring.config.name)配置，否则走DEFAULT_NAMES(application)
**spring.config.name说明：**假如你不喜欢“application.properties”这个默认文件名，你可以重新设定：spring.config.name属性直接指定属性文件名称，spring.config.location属性指定明确路径，但是要注意不能写在application.properties文件里，这样会不起作用，可以写在java -jar xxx.jar --spring.config.name=custom.properties,还可以通过环境变量等方式,yml文件也可以这样
真正加载配置文件的方法：
		private void load(String location, String name, Profile profile,
				DocumentFilterFactory filterFactory, DocumentConsumer consumer) {
			if (!StringUtils.hasText(name)) {
				for (PropertySourceLoader loader : this.propertySourceLoaders) {
					if (canLoadFileExtension(loader, location)) {
						load(loader, location, profile,
								filterFactory.getDocumentFilter(profile), consumer);
						return;
			Set<String> processed = new HashSet<>();
			for (PropertySourceLoader loader : this.propertySourceLoaders) {
				for (String fileExtension : loader.getFileExtensions()) {
					if (processed.add(fileExtension)) {
						loadForFileExtension(loader, location + name, "." + fileExtension,
								profile, filterFactory, consumer);
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loader.getFileExtensions():获取所有支持的文件后缀,loader初始化如下：
		Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
			this.propertySourceLoaders = SpringFactoriesLoader.loadFactories(
					PropertySourceLoader.class, getClass().getClassLoader());
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通过加载jar:spring-boot-2.1.4.RELEASE.jar:META-INF/spring.factories文件下对应内容：
# PropertySource Loaders
org.springframework.boot.env.PropertySourceLoader=\
org.springframework.boot.env.PropertiesPropertySourceLoader,\
org.springframework.boot.env.YamlPropertySourceLoader
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从这里我们可以看到，通过PropertiesPropertySourceLoader和YamlPropertySourceLoader
加载配置文件，具体源码没有细看了，有兴趣自行阅读吧
加载完配置文件，调用方法：addLoadedPropertySources()
至此，springboot加载properties和yml的入口就分析到这里了，细节上肯定不能面面俱到，但是入口知道了，后面就好分析了
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