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);

        }

    }