SpringBoot启动流程源码解析

SpringBoot启动流程源码解析

SpringApplication 的职责是建立一个ApplicationContext
SpringFactoriesLoader加载相似于SPI机制
Spring会去找META-INF/spring.factories文件(文件存在多个),找到对应的实现类的全类名进行加载

SpringApplication建立ApplicationContext`的过程

SpringApplication.initialize()

推断WebEnvironment,

javax.servlet.Servlet
org.springframework.web.context.ConfigurableWebApplicationContext spring会去判断这俩个类是否都存在，都存在的话就会设置webEnvironment为True

初始化ApplicationContextInitializer

经过SpringFactoriesLoader加载机制，将 org.springframework.context.ApplicationContextInitializer对应的Context进行加载 > org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer > org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer > org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer > org.springframework.boot.context.ContextIdApplicationContextInitializer > org.springframework.boot.context.config.DelegatingApplicationContextInitializer > org.springframework.boot.context.embedded.ServerPortInfoApplicationContextInitializer

初始化Listener

经过SpringFactoriesLoader加载机制，将org.springframework.context.ApplicationListener对应的Listener进行加载

org.springframework.boot.autoconfigure.BackgroundPreinitializer org.springframework.cloud.bootstrap.BootstrapApplicationListener org.springframework.cloud.bootstrap.LoggingSystemShutdownListener org.springframework.cloud.context.restart.RestartListener 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.ConfigFileApplicationListener org.springframework.boot.context.config.DelegatingApplicationListener org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener org.springframework.boot.logging.ClasspathLoggingApplicationListener org.springframework.boot.logging.LoggingApplicationListener

推断拥有main方法的类

Spring会拿当前线程的堆栈信息，而后遍历堆栈中的方法帧，查看是否有方法名等于main的方法帧

SpringApplication.run()

加载SpringApplicationRunListener

SpringApplicationRunListener会在在SpringApplication的run()方法中建立ApplicationContext的各个步骤作相应的处理 SpringApplicationRunListeners是SpringApplicationRunListener 的集合类 SpringApplicationRunListeners类负责管理在SpringApplication的run()方法中建立ApplicationContext的各个步骤，一共有5个步骤，starting()->environmentPrepared()->contextPrepared()->contextLoaded()->finished()，在每一个步骤中会调用具体的SpringApplicationRunListener实现类去作相应的事情

经过SpringFactoriesLoader加载机制,将org.springframework.boot.SpringApplicationRunListener对应的SpringApplicationRunListener进行加载

EventPublishingRunListener

• 执行SpringApplicationRunListeners.start()方法 在该方法中利用了SpringApplicationRunListener实现类EventPublishingRunListener向ApplicationListener实现类广播了ApplicationStartedEvent事件

响应了ApplicationStartedEvent事件的ApplicationListener org.springframework.boot.logging.LoggingApplicationListener org.springframework.boot.context.config.DelegatingApplicationListener org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener

建立Environment以及对Environment进行相应的配置

Environment接口表明Spring应用的上下文环境，保存了Spring应用的配置文件和系统属性

• 示例化Environment 会根据是否在Web环境上示例化对应Environment实现类，若是是Web环境，就建立StandardServletEnvironment，不是则建立StandardEnvironment,StandardServletEnvironment对Servlet、JNDI的属性进行了设置
• 将命令行参数配置进Environment当中，具体方法SpringApplication.configurePropertySources()

能够利用SpringApplication.addCommandLineProperties 属性对命令行参数进行禁用

• 设置Environment的activeProfiles，从spring.profiles.active属性中读取
• 执行SpringApplicationRunListeners.environmentPrepared()方法 在该方法中利用了SpringApplicationRunListener实现类EventPublishingRunListener向ApplicationListener实现类广播了ApplicationEnvironmentPreparedEvent事件 >响应了ApplicationEnvironmentPreparedEvent事件的ApplicationListener >org.springframework.cloud.bootstrap.BootstrapApplicationListener >org.springframework.cloud.bootstrap.LoggingSystemShutdownListener >org.springframework.boot.context.config.ConfigFileApplicationListener >org.springframework.boot.context.config.AnsiOutputApplicationListener >org.springframework.boot.logging.LoggingApplicationListener >org.springframework.boot.autoconfigure.BackgroundPreinitializer >org.springframework.boot.logging.ClasspathLoggingApplicationListener >org.springframework.boot.context.config.DelegatingApplicationListener >org.springframework.boot.context.FileEncodingApplicationListener

建立ApplicationContext以及对ApplicationContext进行相应的配置

• 实例化ApplicationContext 会根据是否在Web环境上示例化对应ApplicationContext实现类，若是是Web环境，就建立AnnotationConfigEmbeddedWebApplicationContext，不是则建立AnnotationConfigApplicationContext。
• 将建立好的Environment设置进ApplicationContext
• 对ApplicationContext进行前置处理 若是指定了BeanNameGenerator和ResourceLoader，会设置到ApplicationContext
• 执行ApplicationContextInitializer

org.springframework.cloud.bootstrap.BootstrapApplicationListener$AncestorInitializer org.springframework.cloud.bootstrap.BootstrapApplicationListener$DelegatingEnvironmentDecryptApplicationInitializer org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration$$EnhancerBySpringCGLIB$$d551191c org.springframework.cloud.bootstrap.encrypt.EnvironmentDecryptApplicationInitializer org.springframework.boot.context.config.DelegatingApplicationContextInitializer org.springframework.boot.context.ContextIdApplicationContextInitializer org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer org.springframework.boot.context.embedded.ServerPortInfoApplicationContextInitializer

• 执行SpringApplicationRunListeners.contextPrepared()方法
• 注册命令行参数bean,DefaultApplicationArguments
• 加载sources到ApplicationContext
• 执行SpringApplicationRunListeners.contextLoaded()方法 在这一步首先会将如今的ApplicationListener注册到ApplicationContext当中，而后再利用了SpringApplicationRunListener实现类EventPublishingRunListener向ApplicationListener实现类广播了ApplicationPreparedEvent事件

添加到ApplicationContext的ApplicationListener org.springframework.cloud.bootstrap.BootstrapApplicationListener org.springframework.cloud.bootstrap.LoggingSystemShutdownListener org.springframework.boot.context.config.ConfigFileApplicationListener org.springframework.boot.context.config.AnsiOutputApplicationListener org.springframework.boot.logging.LoggingApplicationListener org.springframework.boot.autoconfigure.BackgroundPreinitializer org.springframework.boot.logging.ClasspathLoggingApplicationListener org.springframework.cloud.context.restart.RestartListener org.springframework.boot.context.config.DelegatingApplicationListener org.springframework.boot.builder.ParentContextCloserApplicationListener org.springframework.boot.ClearCachesApplicationListener org.springframework.boot.context.FileEncodingApplicationListener org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener 响应了ApplicationPreparedEvent事件的ApplicationListener org.springframework.boot.context.config.ConfigFileApplicationListener org.springframework.boot.logging.LoggingApplicationListener org.springframework.cloud.context.restart.RestartListener org.springframework.boot.context.config.DelegatingApplicationListener

• refreshContext()
• afterRefresh() 执行实现了ApplicationRunner和CommandLineRunner的bean
• 执行SpringApplicationRunListeners.finished()方法