2、启动Spring Boot 容器

Spring Boot 几乎所有的工作都是在 SpringApplication 的run方法中完成的，下面给出了run 方法的源码，重点是通过run 方法来了解Spring Boot 的整体工作流程，后续章节会详细分析各个步骤的工作原理和源码。

/**
* Run the Spring application, creating and refreshing a new
 * {@link ApplicationContext}.
 * @param args the application arguments (usually passed from a Java main method)
 * @return a running {@link ApplicationContext}
 */
public ConfigurableApplicationContext run(String... args) {
  // 1、
  StopWatch stopWatch = new StopWatch();
  stopWatch.start();
  ConfigurableApplicationContext context = null;
  FailureAnalyzers analyzers = null;
  // 2、
  configureHeadlessProperty();
  // 3、
  SpringApplicationRunListeners listeners = getRunListeners(args);
  listeners.starting();
  try {
  // 4、
    ApplicationArguments applicationArguments = new DefaultApplicationArguments(
        args);
    ConfigurableEnvironment environment = prepareEnvironment(listeners,
        applicationArguments);
  // 5、
    Banner printedBanner = printBanner(environment);
  // 6、
    context = createApplicationContext();
  // 7、
    analyzers = new FailureAnalyzers(context);
  // 8、
    prepareContext(context, environment, listeners, applicationArguments,
        printedBanner);
  // 9、
    refreshContext(context);
  // 10、
    afterRefresh(context, applicationArguments);
  // 11、
    listeners.finished(context, null);
  // 12、
    stopWatch.stop();
  // 13、
    if (this.logStartupInfo) {
      new StartupInfoLogger(this.mainApplicationClass)
          .logStarted(getApplicationLog(), stopWatch);
    }
    return context;
  }
  catch (Throwable ex) {
  // 14、
    handleRunFailure(context, listeners, analyzers, ex);
    throw new IllegalStateException(ex);
  }
}

源码:

​​run​​  |- 1 stopWatch.start()

 |- 2 configureHeadlessProperty

 |- 3 listeners.starting()

 |- 4 prepareEnvironment

 |- 5 printBanner(environment)

 |- 6 createApplicationContext()

 |- 7 new FailureAnalyzers(context)

 |- 8 prepareContext(...)

 |- 9 refreshContext(context)

 |- 10 afterRefresh

 |- 11 listeners.finished

 |- 12 stopWatch.stop()

 |- 13 new StartupInfoLogger(...).logStarted(...)

 |- 14 handleRunFailure(...)