SpringBoot如何实现上下文初始器加载

private <T> Collection<T> getSpringFactoriesInstances(Class<T> type,
			Class<&#63;>[] parameterTypes, Object... args) {
		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
		// Use names and ensure unique to protect against duplicates
		Set<String> names = new LinkedHashSet<>(
				SpringFactoriesLoader.loadFactoryNames(type, classLoader));
		List<T> instances = createSpringFactoriesInstances(type, parameterTypes,
				classLoader, args, names);
		AnnotationAwareOrderComparator.sort(instances);
		return instances;
}

@Order(Ordered.HIGHEST_PRECEDENCE)
public class HelloWorldApplicationContextInitializer<C extends ConfigurableApplicationContext>
    implements ApplicationContextInitializer<C> {
  @Override
  public void initialize(C applicationContext) {
    System.out.println("ConfigurableApplicationContext.id = "+ applicationContext.getId());
  }
}

public class AfterHelloWorldApplicationContextInitializer implements ApplicationContextInitializer, Ordered {
  @Override
  public void initialize(ConfigurableApplicationContext applicationContext) {
    System.out.println("After application.id = " + applicationContext.getId());
  }
  @Override
  public int getOrder() {
    return Ordered.LOWEST_PRECEDENCE;
  }
}