Spingboot-spring.factories加载流程

背景介绍

有一天我很好奇为什么有些类没配置会自动加载，并生成容器实例，经查发现是spring.factories文件的作用
本文介绍Spingboot-spring.factories加载流程的代码自动加载原理

下面是代码加载流程

SpringApplication.run(App.class, args)


Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");

this.initializers  =  org.springframework.context.ApplicationContextInitializer.class
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"

this.listeners = org.springframework.context.ApplicationListener.class
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"

SpringApplicationRunListener.class
SpringApplicationRunListeners listeners = getRunListeners(args);
org.springframework.boot.context.event.EventPublishingRunListener