SpringBoot-04-SpringApplication构造干了什么

构造SpringApplication就是利用SPI缓存了一些实现类，其他的逻辑都在run方法里面

public SpringApplication(@Nullable ResourceLoader resourceLoader, Class<?>... primarySources) {
	this.resourceLoader = resourceLoader;
	Assert.notNull(primarySources, "'primarySources' must not be null");
	// 启动类
	this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
	this.properties.setWebApplicationType(WebApplicationType.deduce());
	// spring.factories 没有配置
	this.bootstrapRegistryInitializers = new ArrayList<>(
			getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
	// spring.factories 找到ApplicationContextInitializer的实现缓存到initializers
	setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
	// spring.factories 找到ApplicationListener的实现缓存到listeners
	setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
	this.mainApplicationClass = deduceMainApplicationClass();
}