SpringBoot源码学习（一）启动

SpringBoot启动流程

框架的初始化

框架的启动

自动化装配

入口

SpringApplication.run(CoreFacadeApplication.class, args);

然后调用

public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
   return new SpringApplication(primarySources).run(args);
}

初始化SpringApplication

	public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
		//1.配置resourceLoader
		this.resourceLoader = resourceLoader;
		Assert.notNull(primarySources, "PrimarySources must not be null");
		//2.配置PrimarySources
		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
		//3.配置webApplicationType
		this.webApplicationType = org.springframework.boot.WebApplicationType.deduceFromClasspath();
		//4.配置ApplicationContextInitializer,初始化实例
		//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer
		setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
		//5.从类路径下找到ETA-INF/spring.factories配置的所有ApplicationListener，到容器里
		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
		//6.配置mainApplicationClass,从多个配置类中找到有main方法的主配置类
		//在进行main方法的推断时，主要使用了堆栈信息一层层的判断，来获得main方法
		//基本流程就是创建一个运行时异常，然后获得堆栈数组，遍历StackTraceElement数组，判断方法名称是否为“mian”，
		// 如果过是则通过Class.forName()方法创建Class对象
		//这逻辑有点狠
		this.mainApplicationClass = deduceMainApplicationClass();
	}

 

框架启动

	public ConfigurableApplicationContext run(String... args) {
                //1.打印启动时间
		StopWatch stopWatch = new StopWatch();
		stopWatch.start();
		ConfigurableApplicationContext context = null;
		Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
                //2.设置java.awt.headless,Headless模式是系统的一种配置模式。在系统可能缺少显示设备、键盘或鼠标这些外设的情况下可以使用该模式。
		configureHeadlessProperty();
                //3.实例化SpringApplicationRunListener接口实现类//EventPublishingRunListener，设置启动类监听，
//用来在整个启动流程中接收不同执行点事件通知的监听者
		SpringApplicationRunListeners listeners = getRunListeners(args);
		listeners.starting();
		try {
                        //设置ApplicationArguments
			ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
                        //配置环境和相关属性
			ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
			configureIgnoreBeanInfo(environment);
                        //打印banner
			Banner printedBanner = printBanner(environment);
                        //根据环境获取应用上下文类
			context = createApplicationContext();
                        //实例化异常处理器，        //org.springframework.boot.SpringBootExceptionReporter=\
//org.springframework.boot.diagnostics.FailureAnalyzers
			exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
					new Class[] { ConfigurableApplicationContext.class }, context);
                        //准备上下文
			prepareContext(context, environment, listeners, applicationArguments, printedBanner);
                        //刷新上下文
			refreshContext(context);
			afterRefresh(context, applicationArguments);
			stopWatch.stop();
			if (this.logStartupInfo) {
				new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
			}
                        //执行EventPublishingRunListner中的started方法
			listeners.started(context);
                         //回调runners
			callRunners(context, applicationArguments);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, listeners);
			throw new IllegalStateException(ex);
		}

		try {
                        //发送ApplicationReadyEvent
			listeners.running(context);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, null);
			throw new IllegalStateException(ex);
		}
		return context;
	}