SpringBoot启动流程分析

SpringBoot启动流程分析，版本：2.1.1

链接汇总：

（一）SpringApplication对象创建

（二）ApplicationStartingEvent事件的发布监听流程

（三）命令行参数args的封装解析

（四）ApplicationEnvironmentPreparedEvent事件发布

（五）设置系统属性spring.beaninfo.ignore、自定义banner图

（六）创建应用上下文AnnotationConfigServletWebServerApplicationContext

（七）准备应用上下文prepareContext()

（八）刷新应用上下文refreshContext()

（九）最后阶段ApplicationStartedEvent、ApplicationReadyEvent事件发布、callRunners()

.......完结

public SpringApplication(Class... primarySources) {
	this(null, primarySources);
}
 
@SuppressWarnings({ "unchecked", "rawtypes" })
public SpringApplication(ResourceLoader resourceLoader, Class... primarySources) {
	this.resourceLoader = resourceLoader;
        //判断primarySources不能为空
	Assert.notNull(primarySources, "PrimarySources must not be null");
        //将primarySources放入SpringApplication的全局变量primarySources，Set集合中
	this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
        //从类路径中推断应用程序类型放到SpringApplication的全局变量webApplicationType 
	this.webApplicationType = WebApplicationType.deduceFromClasspath();
        //从META-INF/spring.factories文件中获取ApplicationContextInitializer接口的实现类并利用反射创建对象返回放入SpringApplication的全局变量initializers，List集合中
	setInitializers((Collection) getSpringFactoriesInstances(
				ApplicationContextInitializer.class));
        //同上，也是从META-INF/spring.factories文件中获取ApplicationListener接口的实现类并利用反射创建对象返回放入SpringApplication的全局变量listeners，List集合中
	setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
        //通过获取当前调用栈，找到入口方法main所在的类，放入SpringApplication的全局变量mainApplicationClass 
	this.mainApplicationClass = deduceMainApplicationClass();
}

public ConfigurableApplicationContext run(String... args) {
        //StopWatch是org.springframework.util的工具类，可以用来方便的记录程序的运行时间
	StopWatch stopWatch = new StopWatch();
	stopWatch.start();
	ConfigurableApplicationContext context = null;
	Collection exceptionReporters = new ArrayList<>();
        //设置系统属性java.awt.headless为true
	configureHeadlessProperty();
        //从META-INF/spring.factories文件中得到SpringApplicationRunListeners接口的所有实现类
        //然后通过构造方法创建SpringApplicationRunListeners对象。参数就是获取到的接口实现类集合
        //该对象持有一个SpringApplicationRunListener对象的集合,并且封装了SpringApplicationRunListener对象对应的方法，方便统一管理Listener
	SpringApplicationRunListeners listeners = getRunListeners(args);
        //广播事件ApplicationStartingEvent
	listeners.starting();
	try {
                //将args参数进一步封装成ApplicationArguments
		ApplicationArguments applicationArguments = new DefaultApplicationArguments(
				args);
                //构建环境（Environment）
		ConfigurableEnvironment environment = prepareEnvironment(listeners,
				applicationArguments);
                //设置系统属性spring.beaninfo.ignore
		configureIgnoreBeanInfo(environment);
                //打印banner
		Banner printedBanner = printBanner(environment);
                //根据环境类型创建容器
		context = createApplicationContext();
                //SpringApplication启动错误的自定义报告
		exceptionReporters = getSpringFactoriesInstances(
				SpringBootExceptionReporter.class,
				new Class[] { ConfigurableApplicationContext.class }, context);
                //容器准备阶段
		prepareContext(context, environment, listeners, applicationArguments,
				printedBanner);
                //刷新上下文
		refreshContext(context);
                //刷新上下文后调用，扩展接口
		afterRefresh(context, applicationArguments);
		stopWatch.stop();
		if (this.logStartupInfo) {
			new StartupInfoLogger(this.mainApplicationClass)
					.logStarted(getApplicationLog(), stopWatch);
		}
                //发布事件ApplicationStartedEvent
		listeners.started(context);
                //回调ApplicationRunner接口以及CommandLineRunner接口的run方法
		callRunners(context, applicationArguments);
	}
	catch (Throwable ex) {
                //发布ApplicationFailedEvent、ExitCodeEvent事件，异常报告
		handleRunFailure(context, ex, exceptionReporters, listeners);
		throw new IllegalStateException(ex);
	}
	try {
                //发布事件ApplicationReadyEvent
		listeners.running(context);
	}
	catch (Throwable ex) {
		handleRunFailure(context, ex, exceptionReporters, null);
		throw new IllegalStateException(ex);
	}
	return context;
}