springboot启动流程

# springboot启动流程

https://blog.csdn.net/woshilijiuyi/article/details/82219585

## 工程请参考 springboot-simple.zip

## entry
Application entry is `SpringApplication.run(App.class, args);`.

- return new SpringApplication(new Class[] {App.class}).run(args);
  * new SpringApplication(new Class[] {App.class})
    ```text
        this.resourceLoader = resourceLoader;
        Assert.notNull(primarySources, "PrimarySources must not be null");
        this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
        this.webApplicationType = WebApplicationType.deduceFromClasspath();
        setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
        setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
        this.mainApplicationClass = deduceMainApplicationClass();
    ```
    spring.factories:
    - in spring-boot-2.1.6.RELEASE.jar!\META-INF\spring.factories
    - in spring-boot-autoconfigure-2.1.6.RELEASE.jar!/META-INF/spring.factories
    ```text
    SpringFactoriesLoader.loadFactoryNames(ApplicationContextInitializer.class, classLoader):
    names = {LinkedHashSet@1002}  size = 6
     0 = "org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer"
     1 = "org.springframework.boot.context.ContextIdApplicationContextInitializer"
     2 = "org.springframework.boot.context.config.DelegatingApplicationContextInitializer"
     3 = "org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer"
     4 = "org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer"
     5 = "org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener"
    
    SpringFactoriesLoader.loadFactoryNames(ApplicationListener.class, classLoader):
    names = {LinkedHashSet@1118}  size = 10
     0 = "org.springframework.boot.ClearCachesApplicationListener"
     1 = "org.springframework.boot.builder.ParentContextCloserApplicationListener"
     2 = "org.springframework.boot.context.FileEncodingApplicationListener"
     3 = "org.springframework.boot.context.config.AnsiOutputApplicationListener"
     4 = "org.springframework.boot.context.config.ConfigFileApplicationListener"
     5 = "org.springframework.boot.context.config.DelegatingApplicationListener"
     6 = "org.springframework.boot.context.logging.ClasspathLoggingApplicationListener"
     7 = "org.springframework.boot.context.logging.LoggingApplicationListener"
     8 = "org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener"
     9 = "org.springframework.boot.autoconfigure.BackgroundPreinitializer"
    ```

基于如上，可自行创建META-INF\spring.factories文件，并配置自己的ApplicationContextInitializer和ApplicationListener。
    ```text
    org.springframework.context.ApplicationContextInitializer=\
    com.example.SimpleApplicationContextInitializer
    
    org.springframework.context.ApplicationListener=\
    com.example.SimpleApplicationListener
    ```
    
   * ConfigurableApplicationContext run(String... args)
     - `SpringApplicationRunListeners listeners = getRunListeners(args);`
     ```text
        names = {LinkedHashSet@1299}  size = 1
         0 = "org.springframework.boot.context.event.EventPublishingRunListener"
     ```
     - `listeners.starting();`  --> ApplicationStartingEvent
     - `listeners.environmentPrepared(environment);` --> ApplicationEnvironmentPreparedEvent
     - --> ApplicationStartedEvent