看这部分代码，这是springboot启动的run方法的代码
public ConfigurableApplicationContext run(String... args) {
...
// 获取到SpringApplicationRunListeners类
SpringApplicationRunListeners listeners = getRunListeners(args);
// 马上调用starting事件
listeners.starting(bootstrapContext, this.mainApplicationClass);
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
}
private SpringApplicationRunListeners getRunListeners(String[] args) {
Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };
// 跟进去会发现也是SpringFactoriesLoader.loadFactoryNames获取的META-INFO/spring.factories里的SpringApplicationRunListener所有实现类，然后实现类对象集合作为参数再构造一个SpringApplicationRunListeners类包装一下
//SpringApplicationRunListener的实现类只有一个 EventPublishingRunListener
return new SpringApplicationRunListeners(logger,
getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args),
this.applicationStartup);
}
看EventPublishingRunListener的构造方法，就是一个事件发布的类，有事件广播器SimpleApplicationEventMulticaster，也保存了所有的ApplicationListener监听器，ApplicationListener监听器是构造SpringApplication对象的时候从META-INFO/spring.factories里获取的，然后宝SpringApplication的成员变量listeners中的。
public EventPublishingRunListener(SpringApplication application, String[] args) {
this.application = application;
this.args = args;
this.initialMulticaster = new SimpleApplicationEventMulticaster();
for (ApplicationListener<?> listener : application.getListeners()) {
this.initialMulticaster.addApplicationListener(listener);
}
}
在spring-boot.jar包中的META-INFO/spring.factories里可以看到ApplicationListener有这么多实现类，这里关注EnvironmentPostProcessorApplicationListener，环境配置处理的监听器。
org.springframework.context.ApplicationListener=\
org.springframework.boot.ClearCachesApplicationListener,\
org.springframework.boot.builder.ParentContextCloserApplicationListener,\
org.springframework.boot.context.FileEncodingApplicationListener,\
org.springframework.boot.context.config.AnsiOutputApplicationListener,\
org.springframework.boot.context.config.DelegatingApplicationListener,\
org.springframework.boot.context.logging.LoggingApplicationListener,\
org.springframework.boot.env.EnvironmentPostProcessorApplicationListener,\
org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener
starting事件会广播所有ApplicationListener的starting事件。EnvironmentPostProcessorApplicationListener的onApplicationEvent事件监听方法不会处理ApplicationStartingEvent事件。所以不在这里。
public void starting(ConfigurableBootstrapContext bootstrapContext) {
this.initialMulticaster
.multicastEvent(new ApplicationStartingEvent(bootstrapContext, this.application, this.args));
}
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
}
if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent((ApplicationPreparedEvent) event);
}
if (event instanceof ApplicationFailedEvent) {
onApplicationFailedEvent((ApplicationFailedEvent) event);
}
}
而是在这里：prepareEnvironment预处理环境方法里，触发了environmentPrepared事件。
public ConfigurableApplicationContext run(String... args) {
...
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
}
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
DefaultBootstrapContext bootstrapContext, ApplicationArguments applicationArguments) {
// Create and configure the environment
ConfigurableEnvironment environment = getOrCreateEnvironment();
configureEnvironment(environment, applicationArguments.getSourceArgs());
ConfigurationPropertySources.attach(environment);
// 触发environmentPrepared事件
listeners.environmentPrepared(bootstrapContext, environment);
DefaultPropertiesPropertySource.moveToEnd(environment);
configureAdditionalProfiles(environment);
bindToSpringApplication(environment);
if (!this.isCustomEnvironment) {
environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
deduceEnvironmentClass());
}
ConfigurationPropertySources.attach(environment);
return environment;
}
// 所有监听器触发environmentPrepared方法，SpringApplicationRunListener只有一个实现类EventPublishingRunListener，所以这里触发EventPublishingRunListener的environmentPrepared方法
void environmentPrepared(ConfigurableBootstrapContext bootstrapContext, ConfigurableEnvironment environment) {
doWithListeners("spring.boot.application.environment-prepared",
(listener) -> listener.environmentPrepared(bootstrapContext, environment));
}
// EventPublishingRunListener发布事件ApplicationEnvironmentPreparedEvent
@Override
public void environmentPrepared(ConfigurableBootstrapContext bootstrapContext,
ConfigurableEnvironment environment) {
this.initialMulticaster.multicastEvent(
new ApplicationEnvironmentPreparedEvent(bootstrapContext, this.application, this.args, environment));
}
进入了第一个事件方法里
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
}
if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent((ApplicationPreparedEvent) event);
}
if (event instanceof ApplicationFailedEvent) {
onApplicationFailedEvent((ApplicationFailedEvent) event);
}
}
private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
ConfigurableEnvironment environment = event.getEnvironment();
SpringApplication application = event.getSpringApplication();
for (EnvironmentPostProcessor postProcessor : getEnvironmentPostProcessors(event.getBootstrapContext())) {
postProcessor.postProcessEnvironment(environment, application);
}
}
在构造EnvironmentPostProcessorApplicationListener对象的时候，EnvironmentPostProcessorApplicationListener的成员变量postProcessorsFactory就赋值了EnvironmentPostProcessorsFactory ，并且这个EnvironmentPostProcessorsFactory 维护了所有的EnvironmentPostProcessor实现类，从META-INF/spring.factories里获取的。
public EnvironmentPostProcessorApplicationListener() {
this(EnvironmentPostProcessorsFactory
.fromSpringFactories(EnvironmentPostProcessorApplicationListener.class.getClassLoader()));
}
static EnvironmentPostProcessorsFactory fromSpringFactories(ClassLoader classLoader) {
return new ReflectionEnvironmentPostProcessorsFactory(
SpringFactoriesLoader.loadFactoryNames(EnvironmentPostProcessor.class, classLoader));
}
可以看到有这么多实现类，重点看ConfigDataEnvironmentPostProcessor，这是解析配置文件的。
org.springframework.boot.env.EnvironmentPostProcessor=\
org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor,\
org.springframework.boot.env.RandomValuePropertySourceEnvironmentPostProcessor,\
org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor,\
org.springframework.boot.env.SystemEnvironmentPropertySourceEnvironmentPostProcessor,\
org.springframework.boot.reactor.DebugAgentEnvironmentPostProcessor
回头看这里，循环调用所有的EnvironmentPostProcessor 的postProcessEnvironment方法，自然会调用ConfigDataEnvironmentPostProcessor的postProcessEnvironment方法
private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
ConfigurableEnvironment environment = event.getEnvironment();
SpringApplication application = event.getSpringApplication();
for (EnvironmentPostProcessor postProcessor : getEnvironmentPostProcessors(event.getBootstrapContext())) {
postProcessor.postProcessEnvironment(environment, application);
}
}
ConfigDataEnvironmentPostProcessor的postProcessEnvironment方法
会构建一个ConfigDataEnvironment对象，这个对象比较重要
void postProcessEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
Collection<String> additionalProfiles) {
try {
this.logger.trace("Post-processing environment to add config data");
resourceLoader = (resourceLoader != null) ? resourceLoader : new DefaultResourceLoader();
getConfigDataEnvironment(environment, resourceLoader, additionalProfiles).processAndApply();
}
catch (UseLegacyConfigProcessingException ex) {
this.logger.debug(LogMessage.format("Switching to legacy config file processing [%s]",
ex.getConfigurationProperty()));
postProcessUsingLegacyApplicationListener(environment, resourceLoader);
}
}
ConfigDataEnvironment getConfigDataEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
Collection<String> additionalProfiles) {
return new ConfigDataEnvironment(this.logFactory, this.bootstrapContext, environment, resourceLoader,
additionalProfiles);
}
ConfigDataEnvironment的静态块中可以看到，定义好了所有的配置文件存放的路径。一共有6个。也就是说会读取这6个路径下的yml文件或properties文件，并且有
static final ConfigDataLocation[] DEFAULT_SEARCH_LOCATIONS;
static {
List<ConfigDataLocation> locations = new ArrayList<>();
locations.add(ConfigDataLocation.of("optional:classpath:/"));
locations.add(ConfigDataLocation.of("optional:classpath:/config/"));
locations.add(ConfigDataLocation.of("optional:file:./"));
locations.add(ConfigDataLocation.of("optional:file:./config/"));
locations.add(ConfigDataLocation.of("optional:file:./config/*/"));
DEFAULT_SEARCH_LOCATIONS = locations.toArray(new ConfigDataLocation[0]);
};
org.springframework.boot.context.config.ConfigDataLocationResolver=\
org.springframework.boot.context.config.ConfigTreeConfigDataLocationResolver,\
org.springframework.boot.context.config.StandardConfigDataLocationResolver
# ConfigData Loaders
org.springframework.boot.context.config.ConfigDataLoader=\
org.springframework.boot.context.config.ConfigTreeConfigDataLoader,\
org.springframework.boot.context.config.StandardConfigDataLoader
