springboot 源码笔记

1.springAppication构造器

　　基于getSpringFactoriesInstances方法构造如下类(获取文件内容在META-INF/spring.factories文件中)

　　1.1 初始化ApplicationContextInitializer.class

# Application Context Initializers
org.springframework.context.ApplicationContextInitializer=
org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,
org.springframework.boot.context.ContextIdApplicationContextInitializer,
org.springframework.boot.context.config.DelegatingApplicationContextInitializer,
org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer

　　1.2 初始化ApplicationListener.class

# Application Listeners
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.ConfigFileApplicationListener,
org.springframework.boot.context.config.DelegatingApplicationListener,
org.springframework.boot.context.logging.ClasspathLoggingApplicationListener,
org.springframework.boot.context.logging.LoggingApplicationListener,
org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener

2.run方法

		StopWatch stopWatch = new StopWatch();//构造时间观察器
		stopWatch.start();// 打印一个开始时间
		ConfigurableApplicationContext context = null;
		Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
		configureHeadlessProperty();// 配置headless 依据java.awt.headless
		SpringApplicationRunListeners listeners = getRunListeners(args);// 解析如下
		// getSpringFactoriesInstances方法获取SpringApplicationRunListener.class对象->EventPublishingRunListener对象
			// EventPublishingRunListener对象初始化时,构造器内会执行下面的逻辑
				//SimpleApplicationEventMulticaster广播器初始化,并且将listener设置到广播器中
		// 将上面获取到的EventPublishingRunListener对象对象添加到SpringApplicationRunListeners对象中
		listeners.starting(); // 解析如下
		// 调用EventPublishingRunListener对象的starting方法
			// 将ApplicationStartingEvent广播出去 SimpleApplicationEventMulticaster->multicastEvent方法
			// 调用getApplicationListeners方法获取所有listeners,然后循环广播
			// 调用支持事件的listener的listener.onApplicationEvent(event);方法,驱动listener巡行
			// 此处支持的listener如下
				// org.springframework.boot.logging.LoggingApplicationListener, 
				// org.springframework.boot.autoconfigure.BackgroundPreinitializer, 
				// org.springframework.boot.context.config.DelegatingApplicationListener, 
				// org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener
		try {
			ApplicationArguments applicationArguments = new DefaultApplicationArguments(
					args);
			// 创建一个DefaultApplicationArguments对象,构造器中构造了一个新的SOURCE对象
			// 根据SOURCE对象的继承结构->SimpleCommandLinePropertySource->parse方法
				// 如果args是–开头的,就加入OptionArg中,否则加入到NonOptionArg中
			// CommandLinePropertySource构造其中commandLineArgs存入source
			ConfigurableEnvironment environment = prepareEnvironment(listeners,
					applicationArguments);
			// 参照下面的prepareEnvironment方法分析
			configureIgnoreBeanInfo(environment);
			Banner printedBanner = printBanner(environment); // 打印banner
			context = createApplicationContext();
			// 创建applicationContext
			// 添加AnnotationTypeFilter–>Component 添加AnnotationTypeFilter –> ManagedBean 添加AnnotationTypeFilter –> javax.inject.Named
			// 

			exceptionReporters = getSpringFactoriesInstances(
					SpringBootExceptionReporter.class,
					new Class[] { ConfigurableApplicationContext.class }, context);
			// 异常处理
			prepareContext(context, environment, listeners, applicationArguments,
					printedBanner);
			// 
			refreshContext(context);
			// 
			afterRefresh(context, applicationArguments);
			stopWatch.stop();
			if (this.logStartupInfo) {
				new StartupInfoLogger(this.mainApplicationClass)
						.logStarted(getApplicationLog(), stopWatch);
			}
			listeners.started(context);
			callRunners(context, applicationArguments);
		}

　　

 prepareEnvironment方法分析

private ConfigurableEnvironment prepareEnvironment(
			SpringApplicationRunListeners listeners,
			ApplicationArguments applicationArguments) {
		// Create and configure the environment
		ConfigurableEnvironment environment = getOrCreateEnvironment();
		// 获取或者创建ConfigurableEnvironment 构造environment对象 继承AbstractEnvironment
		// AbstractEnvironment构造器中调用customizePropertySources方法
		// StandardEnvironment对象:配置systemEnvironment systemProperties
		// StandardServletEnvironment对象:配置servletContextInitParams servletConfigInitParams jndiProperties
		configureEnvironment(environment, applicationArguments.getSourceArgs());
		// 配置环境的信息
		// configurePropertySources 配置PropertySources 
			// commandLineArgs、servletConfigInitParams、servletContextInitParams、jndiProperties（如果存在）、
			// systemProperties、systemEnvironment、defaultProperties（如果存在）
		// configureProfiles 配置Profiles
			// 至于哪个具体的配置文件会被加载，需要在application.properties文件中通过spring.profiles.active属性来设置，其值对应{profile}值。
			//  application-dev.properties：开发环境  application-test.properties：测试环境 application-prod.properties：生产环境
		listeners.environmentPrepared(environment);
		// 通知所有的观察者,发送ApplicationEnvironmentPreparedEvent事件.
			// org.springframework.boot.context.config.ConfigFileApplicationListener, 
			// org.springframework.boot.context.config.AnsiOutputApplicationListener, 
			// org.springframework.boot.logging.LoggingApplicationListener, 
			// org.springframework.boot.logging.ClasspathLoggingApplicationListener, 
			// org.springframework.boot.autoconfigure.BackgroundPreinitializer, 
			// org.springframework.boot.context.config.DelegatingApplicationListener, 
			// org.springframework.boot.context.FileEncodingApplicationListener
		// 
		bindToSpringApplication(environment);
		if (!this.isCustomEnvironment) {
			environment = new EnvironmentConverter(getClassLoader())
					.convertEnvironmentIfNecessary(environment, deduceEnvironmentClass());
		}
		ConfigurationPropertySources.attach(environment);
		return environment;
	}

　　

prepareContext分析

private void prepareContext(ConfigurableApplicationContext context,
        ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
        ApplicationArguments applicationArguments, Banner printedBanner) {
    // 1. 上下文设置环境
    context.setEnvironment(environment);
    // 2. 调用postProcessApplicationContext方法设置上下文的beanNameGenerator和resourceLoader(如果SpringApplication有的话)
    postProcessApplicationContext(context);
    // 3. 拿到之前实例化SpringApplication对象的时候设置的ApplicationContextInitializer，调用它们的initialize方法，对上下文做初始化
    applyInitializers(context);
    // 4. contextPrepareds 是一个空实现 
    listeners.contextPrepared(context);
    // 5. 打印启动日志
    if (this.logStartupInfo) {
        logStartupInfo(context.getParent() == null);
        logStartupProfileInfo(context);
    }

    // Add boot specific singleton beans
    // 6. 日志往上下文的beanFactory中注册一个singleton的bean，bean的名字是springApplicationArguments，bean的实例是之前实例化的ApplicationArguments对象
    context.getBeanFactory().registerSingleton("springApplicationArguments",
            applicationArguments);
    // 如果之前获取的printedBanner不为空，那么往上下文的beanFactory中注册一个singleton的bean，bean的名字是springBootBanner，bean的实例就是这个printedBanner
    if (printedBanner != null) {
        context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
    }

    // Load the sources
    Set<Object> sources = getSources();
    Assert.notEmpty(sources, "Sources must not be empty");
    // 7. 调用load方法注册启动类的bean定义，也就是调用SpringApplication.run(Application.class, args);的类，SpringApplication的load方法内会创建BeanDefinitionLoader的对象，并调用它的load()方法
    load(context, sources.toArray(new Object[sources.size()]));
    // 8. 调用listeners的contextLoaded方法，说明上下文已经加载，该方法先找到所有的ApplicationListener，遍历这些listener，如果该listener继承了ApplicationContextAware类，那么在这一步会调用它的setApplicationContext方法，设置context
    listeners.contextLoaded(context);
}

　　

# Environment Post Processors
org.springframework.boot.env.EnvironmentPostProcessor=
org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,
org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor,
org.springframework.boot.env.SystemEnvironmentPropertySourceEnvironmentPostProcessor

　　

1.SpringFactoriesLoader类

　　loadFactoryNames->loadSpringFactories->META-INF/spring.factories

　　位置:spring-boot-2.0.5.RELEASE-sources.jar目录下