apollo-client-config-data/src/main/java/com/ctrip/framework/apollo/config/data/listener/ApolloSpringApplicationRegisterListener.java/ApolloSpringApplicationRegisterListener/onApplicationEvent
class ApolloSpringApplicationRegisterListener:  @Override
  public void onApplicationEvent(ApplicationStartingEvent event) {
    ConfigurableBootstrapContext bootstrapContext = event.getBootstrapContext();
    bootstrapContext.registerIfAbsent(SpringApplication.class,
        InstanceSupplier.of(event.getSpringApplication()));
  }