Spring官方文檔閱讀筆記

1. The IoC Container

1.1. Introduction to the Spring IoC Container and Beans

• In Spring, the objects that form the backbone of your application and that are managed by the Spring IoC container are called beans.
• A bean is an object that is instantiated, assembled, and otherwise managed by a Spring IoC container.
• Beans, and the dependencies among them, are reflected in the configuration metadata used by a container.

Spring創建Bean的過程

• AbstractApplicationContext.prepareRefresh()：環境準備
• AbstractApplicationContext.obtainFreshBeanFactory()：創建beanFactory
  • GenericApplicationContext.getBeanFactory()
• AbstractApplicationContext.prepareBeanFactory()：beanFactory準備
• AnnotationConfigEmbeddedWebApplicationContext.postProcessBeanFactory()
  • EmbeddedWebApplicationContext.postProcessBeanFactory()：設置beanPostProcessor爲WebApplicationContextServletContextAwareProcessor對象；
• AbstractApplicationContext.invokeBeanFactoryPostProcessors()
  • PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors()
• AbstractApplicationContext.registerBeanPostProcessors() 註冊beanPostProcessor；
  • PostProcessorRegistrationDelegate.registerBeanPostProcessors()
• AbstractApplicationContext.initMessageSource()：初始化容器中的messageSource；
• AbstractApplicationContext.initApplicationEventMulticaster()：初始化事件分發器；
• EmbeddedWebApplicationContext.onRefresh()
  • EmbeddedWebApplicationContext.createEmbeddedServletContainer()
• AbstractApplicationContext.registerListeners()：註冊事件監聽器
• AbstractApplicationContext.finishBeanFactoryInitialization()：
  • DefaultListableBeanFactory.preInstantiateSingletons();

    • AbstractBeanFactory.getBean()

    • AbstractBeanFactory.doGetBean()

    • transformedBeanName()：轉化BeanName

    • getMergedLocalBeanDefinition()：合併RootBeanDefinition

    • beforePrototypeCreation()/afterPrototypeCreation()解決循環依賴

    • 創建實例：

    • AbstractAutowireCapableBeanFactory.createBean();

    • AbstractAutowireCapableBeanFactory.doCreateBean();

    • AbstractAutowireCapableBeanFactory.createBeanInstance();

    • AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod();工廠方法創建對象；

    • AbstractAutowireCapableBeanFactory.autowireConstructor();推斷構造函數；

    • AbstractAutowireCapableBeanFactory.instantiateBean();無參構造函數；

    • 屬性注入populateBean()

    • 初始化：

      • invokeAwareMethods()
      • BeanPostProcessor.postProcessBeforeInstantiation()
      • invokeInitMethods()
        • 1、判斷bean是否繼承了InitializingBean，如果繼承接口，執行afterPropertiesSet()方法，
        • 2、獲得是否設置了init-method屬性，如果設置了，就執行設置的方法
      • BeanPostProcessor.postProcessAfterInstantiation() 鉤子

    • 類型轉化convertIfNecessary()

• AbstractApplicationContext.finishRefresh()：refresh完成

Spring銷燬Bean的過程

• LiveBeansView.unregisterApplicationContext()：卸載註冊的IOC對象
• AbstractApplicationContext.destroyBeans()：銷燬bean
  • DefaultSingletonBeanRegistry.destroySingletons()：銷燬單粒bean；
    • DefaultSingletonBeanRegistry.destroySingleton()
      • DefaultSingletonBeanRegistry.destroyBean()
        • DisposableBean.destroy()
• AbstractApplicationContext.closeBeanFactory()：銷燬beanFactory對象

Spring創建Bean的詳細過程

Mybatis執行SQL過程

• MapperProxy.invoke()
• MapperMethod.execute()
• MapperMethod.executeForMany()
• SqlSessionTemplate.selectList()
• SqlSessionTemplate.invoke()
• DefaultSqlSession.selectList()
• this.executor.query()
• this.query()先判斷緩存是否爲空，若爲空
• this.delegate.query()
• BaseExecutor.query()
• BaseExecutor.queryFromDatabase()
• BaseExecutor.doQuery()
• RoutingStatementHandler.query()
• PreparedStatementHandler.query()
• PreparedStatementLogger.invoke()
• StatementFacade.invoke()
• PreparedStatement.execute()
• PreparedStatement.executeInternal()
• MySQLConnection.execSQL()
• MysqlIO.sqlQueryDirect()
• MysqlIO.sendCommand()
• MysqlIO.send()
• DefaultResultSetHandler.handleResultSets()
• DefaultResultSetHandler.handleResultSet()

@EnableAutoConfiguration註解

• @EnableAutoConfiguration註解中import了EnableAutoConfigurationImportSelector類。
• SpringBoot啓動過程的函數調用：
  • SpringApplication.run()
  • SpringApplication.createApplicationContext()註冊ConfigurationClassPostProcessor到Spring容器中；
    • AnnotatedBeanDefinitionReader.AnnotatedBeanDefinitionReader()構造函數；
      • AnnotationConfigUtils.registerAnnotationConfigProcessors()
        • RootBeanDefinition.RootBeanDefinition()；
          • AnnotationConfigUtils.registerPostProcessor();
  • SpringApplication.refreshContext()調用
    • AbstractApplicationContext.refresh()
      • AbstractApplicationContext.invokeBeanFactoryPostProcessors()
      • AutoConfigurationImportSelector.selectImports()
      • AutoConfigurationImportSelector.getCandidateConfigurations()
      • SpringFactoriesLoader.loadFactoryNames()加載spring-boot-autoconfigure.jar/META-INF/spring.factories文件中的org.springframework.boot.autoconfigure.EnableAutoConfiguration對應的value；