Spring Boot启动流程详解

Spring Boot是一个基于Spring框架的快速开发工具，它可以帮助我们快速搭建一个可运行的Spring应用。本文将详细介绍Spring Boot的启动流程，帮助大家更好地理解Spring Boot的工作原理。

一、Spring Boot启动流程概述

Spring Boot的启动流程可以分为以下几个阶段：

• 初始化配置

• 创建应用程序上下文

• 刷新上下文（启动核心）

• 通知监听者-启动程序完成

public ConfigurableApplicationContext run(String... args) {
   
        long startTime = System.nanoTime();
        DefaultBootstrapContext bootstrapContext = this.createBootstrapContext();
        ConfigurableApplicationContext context = null;
        this.configureHeadlessProperty();
        SpringApplicationRunListeners listeners = this.getRunListeners(args);
        listeners.starting(bootstrapContext, this.mainApplicationClass);

        try {
   
          // 获取args参数对象
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
             // 读取Springboot配置文件并创建Environment对象
        // 这里创建的Environment对象实际为ConfigurableEnvironment
            ConfigurableEnvironment environment = this.prepareEnvironment(listeners, bootstrapContext, applicationArguments);
            this.configureIgnoreBeanInfo(environment);
             // 打印Banner图标
            Banner printedBanner = this.printBanner(environment);
             // 创建ApplicationContext应用行下文，即创建容器
            context = this.createApplicationContext();
            context.setApplicationStartup(this.applicationStartup);
             // 准备容器
            this.prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
             // 初始化容器
            this.refreshContext(context);
            this.afterRefresh(context, applicationArguments);
            Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
            if (this.logStartupInfo) {
   
                (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), timeTakenToStartup);
            }
 		// 调用运行时监听器的started()方法
        // 该方法需要在应用程序启动后，CommandLineRunners和ApplicationRunners被调用前执行
            listeners.started(context, timeTakenToStartup);
            this.callRunners(context, applicationArguments);
        } catch (Throwable var12) {
   
            this.handleRunFailure(context, var12, listeners);
            throw new IllegalStateException(var12);
        }

        try {
   
            Duration timeTakenToReady = Duration.ofNanos