Spring源码分析(11)——SpringBoot源码

@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
  this.resourceLoader = resourceLoader;
  Assert.notNull(primarySources, "PrimarySources must not be null");
  // 这里就是MyApplication
  this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
  // 判断是否是web应用
  this.webApplicationType = deduceWebApplicationType();
  // spring.factories文件中寻找ApplicationContextInitializer的实现类，如org.springframework.context.ApplicationContextInitializer=com.**.PropertyInitializer
  setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
  // spring.factories文件中寻找ApplicationListener的实现类，如org.springframework.context.ApplicationListener=org.springframework.boot.context.config.DelegatingApplicationListener
  setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
  // 寻找当前运行的类，这里就是MyApplication
  this.mainApplicationClass = deduceMainApplicationClass();
}

public ConfigurableApplicationContext run(String... args) {
  // 创建任务观察记录器，记录运行时间
  StopWatch stopWatch = new StopWatch();
  stopWatch.start();
  ConfigurableApplicationContext context = null;
  Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
  configureHeadlessProperty();
  // 获取RunListeners
  SpringApplicationRunListeners listeners = getRunListeners(args);
  // 封装成ApplicationStartedEvent，然后广播给刚才从spring.factories文件中初始化的ApplicationListener
  listeners.starting();
  try {
    // 构造一个应用程序参数持有类
    ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
    // 准备系统运行环境
    ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);
    configureIgnoreBeanInfo(environment);
    // 在控制台打印Spring banner
    Banner printedBanner = printBanner(environment);
    // 创建ApplicationContext容器，这里的类型是AnnotationConfigEmbeddedWebApplicationContext
    // 注意，在普通Spring框架中，启动的类型是XmlWebApplicationContext，和SpringBoot的容器类型不一样
    context = createApplicationContext();
    // 创建SpringBoot错误报错类
    exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
        new Class[] { ConfigurableApplicationContext.class }, context);
    // 对刚创建的ApplicationContext做一些预处理，包含对所有ApplicationContextInitializer的初始化调用
    prepareContext(context, environment, listeners, applicationArguments,printedBanner);
    // ApplicationContext容器的刷新，这里的内容可参见ApplicationContext的内容
    // 所有Bean的读取、解析、注册、实例化，tomcat容器的启动等操作都是在这里完成的
    refreshContext(context);
    // 容器刷新的后处理
    afterRefresh(context, applicationArguments);
    // 停止任务观察记录器，停止记录运行时间
    stopWatch.stop();
    // 输出SpringBoot启动时间
    if (this.logStartupInfo) {
      new StartupInfoLogger(this.mainApplicationClass)
          .logStarted(getApplicationLog(), stopWatch);
    }
    listeners.started(context);
    callRunners(context, applicationArguments);
  }
  catch (Throwable ex) {
    handleRunFailure(context, ex, exceptionReporters, listeners);
    throw new IllegalStateException(ex);
  }

  try {
    listeners.running(context);
  }
  catch (Throwable ex) {
    handleRunFailure(context, ex, exceptionReporters, null);
    throw new IllegalStateException(ex);
  }
  return context;
}

@Bean(name = {"dispatcherServlet"})
public DispatcherServlet dispatcherServlet() {
    DispatcherServlet dispatcherServlet = new DispatcherServlet();
    dispatcherServlet.setDispatchOptionsRequest(this.webMvcProperties.isDispatchOptionsRequest());
    dispatcherServlet.setDispatchTraceRequest(this.webMvcProperties.isDispatchTraceRequest());
    dispatcherServlet.setThrowExceptionIfNoHandlerFound(this.webMvcProperties.isThrowExceptionIfNoHandlerFound());
    return dispatcherServlet;
}