1.3 一个简单的启动类

springboot启动过程 - 图2

2.源码大致解析

2.1 主方法(MAIN)

  1. 1.创建一个Spring应用 
  2.     new SpringApplication(primarySources).run(args)
  3.     2.new SpringApplication
  4.         public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
  5.             2.1 资源加载
  6.             this.resourceLoader = resourceLoader;
  7.             Assert.notNull(primarySources, "PrimarySources must not be null");
  8.             2.2 将主类放入linkedHastSet当中
  9.             this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
  10.             2.3 应用类型的选择
  11.             this.webApplicationType = WebApplicationType.deduceFromClasspath();
  12.             2.4 设置初始化(构造)器
  13.             setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
  14.             2.5 设置（应用）监听器 
  15.             setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
  16.             2.6 配置应用的主方法所在类
  17.             this.mainApplicationClass = deduceMainApplicationClass();
  18.         }
  1. 3. run(args);
  2.         public ConfigurableApplicationContext run(String... args) {
  3.             3.1 计时器开始
  4.             StopWatch stopWatch = new StopWatch();
  5.             stopWatch.start();
  6.             ConfigurableApplicationContext context = null;
  7.             Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
  8.             3.2 配置参数
  9.             configureHeadlessProperty();
  10.             3.3 配置运行监听器
  11.             SpringApplicationRunListeners listeners = getRunListeners(args);
  12.             3.4 监听器开始工作
  13.             listeners.starting();
  14.             try {
  15.                 ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
  16.                 3.5准备环境--监听器和应用参数
  17.                 ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
  18.                 3.6配置忽略的Bean信息
  19.                 configureIgnoreBeanInfo(environment);
  20.                 3.7打印图案
  21.                 Banner printedBanner = printBanner(environment);
  22.                 3.8 创建应用上下文
  23.                 context = createApplicationContext();
  24.                 3.9 异常报告
  25.                 exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
  26.                         new Class[] { ConfigurableApplicationContext.class }, context);
  27.                 3.10 准备上下文(将启动类注册到BeanDefinition)
  28.                 prepareContext(context, environment, listeners, applicationArguments, printedBanner);
  29.                 3.11 刷新上下文
  30.                 refreshContext(context);
  31.                 3.12 刷新上下文善后
  32.                 afterRefresh(context, applicationArguments);
  33.                 3.13 计时器结束
  34.                 stopWatch.stop();
  35.                 if (this.logStartupInfo) {
  36.                     new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
  37.                 }
  38.                 3.14 启动所有监听器
  39.                 listeners.started(context);
  40.                 callRunners(context, applicationArguments);
  41.             }
  42.             catch (Throwable ex) {
  43.                 3.15 处理运行失败
  44.                 handleRunFailure(context, ex, exceptionReporters, listeners);
  45.                 throw new IllegalStateException(ex);
  46.             }
  48.             try {
  49.                 3.16 将应用上下文传递给每一个监听器
  50.                 listeners.running(context);
  51.             }
  52.             catch (Throwable ex) {
  53.                 handleRunFailure(context, ex, exceptionReporters, null);
  54.                 throw new IllegalStateException(ex);
  55.             }
  56.             return context;
  57.         }

2.2 SPRINGBOOTAPPLICATOIN注解

  1. 基本属性 1.1 exclude 排除不需要自动配置的类 1.2 excludeName 排除不需要自动配置的类的类名 1.3 scanBasePackages 扫描基本包(被指定的包的子包也会包扫描到) 1.4 scanBasePackageClasses 扫描类所在包下的所有组件 2. 注解 2.1 SpringBootConfiguration 表明这个类提供一个Spring Boot Application(Indicates that a class provides Spring Boot application) 2.2 EnableAutoConfiguration 允许自动配置(将根据所导入的jar进行自动配置) 2.3 ComponentScan 扫描哪些包或者类所在包的组件 (Repeatable 允许重复配置)