springboot启动流程源码分析

启动分为两部分，先创建Application然后调用实例的run方法。

1、new Application执行流程

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {

this.sources = new LinkedHashSet();

this.bannerMode = Mode.CONSOLE;

this.logStartupInfo = true;

this.addCommandLineProperties = true;

this.addConversionService = true;

this.headless = true;

this.registerShutdownHook = true;

this.additionalProfiles = new HashSet();

this.isCustomEnvironment = false;

this.lazyInitialization = false;

this.resourceLoader = resourceLoader;

Assert.notNull(primarySources, "PrimarySources must not be null");

//保存主配置类

this.primarySources = new LinkedHashSet(Arrays.asList(primarySources));

//判断应用是否是web应用环境

this.webApplicationType = WebApplicationType.deduceFromClasspath();

//从类路径下META-INF的spring.factoris文件里找到所有的ApplicationContextInitializer，然后保存起来

this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));

//从类路径下的META-INF下的spring.factories下找到所有的ApplicationListener类，保存起来

this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));

//从几个配置类当中找到主配置类

this.mainApplicationClass = this.deduceMainApplicationClass();

}

2.SpringApplication.run(args)流程

public ConfigurableApplicationContext run(String... args) {

StopWatch stopWatch = new StopWatch();

stopWatch.start();

ConfigurableApplicationContext context = null;

Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();

this.configureHeadlessProperty();

//获取SpringApplicationRunListeners，从类路径META-INF的spring.factories找所有的SpringApplicationRunListener

SpringApplicationRunListeners listeners = this.getRunListeners(args);

//遍历所有的SpringApplicationRunListener的start()方法

listeners.starting();

Collection exceptionReporters;

try {

//封装命令行参数

ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);

//准备环境，创建完环境之后调用SpringApplicationRunListener的environmentPrepared方法，表示环境准备完成

ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);

this.configureIgnoreBeanInfo(environment);

//控制台打印banner图标

Banner printedBanner = this.printBanner(environment);

//创建ApplicationContext，决定创建web的ioc容器还是普通的ioc容器

context = this.createApplicationContext();

exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);

//准备上下文环境将environment保存到ioc容器当中，而且applyInitializers();

//applyInitializers() 调用之前加载所有的ApplicationContextInitializer的initialize()方法

//同时调用之前加载所有的SpringApplicationRunListener的contextPrepared()方法

this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);

//prepareContext运行完成时再调用所有的SpringApplicationRunListeners的contextLoaded()方法

//重构ioc容器，就是ioc容器的初始化(如果是web应用，还会创建嵌入式的tomcat)

this.refreshContext(context);

this.afterRefresh(context, applicationArguments);

stopWatch.stop();

if (this.logStartupInfo) {

(new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);

}

//回调所有的SpringApplicationRunListeners的start()方法

listeners.started(context);

//调用ApplicationRunner和CommandLineRunner的方法

this.callRunners(context, applicationArguments);

} catch (Throwable var10) {

this.handleRunFailure(context, var10, exceptionReporters, listeners);

throw new IllegalStateException(var10);

}

try {

//调用所有的SpringApplicationRunListeners的running()方法

listeners.running(context);

//整个springboot应用启动以后返回启动的ioc容器

return context;

} catch (Throwable var9) {

this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);

throw new IllegalStateException(var9);

}