springboot源码之

prepareContext(context, environment, listeners, applicationArguments,
                    printedBanner);

applyInitializers(context);

protected void applyInitializers(ConfigurableApplicationContext context) {
        for (ApplicationContextInitializer initializer : getInitializers()) {
            Class<?> requiredType = GenericTypeResolver.resolveTypeArgument(
                    initializer.getClass(), ApplicationContextInitializer.class);
            Assert.isInstanceOf(requiredType, context, "Unable to call initializer.");
            initializer.initialize(context);
        }
    }

//springApplication的初始化中有这个方法，逻辑是去spring.factories中取ApplicationContextInitializer.class
setInitializers((Collection) getSpringFactoriesInstances(
                ApplicationContextInitializer.class));

org.springframework.context.ApplicationContextInitializer=\
org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
org.springframework.boot.context.ContextIdApplicationContextInitializer,\
org.springframework.boot.context.config.DelegatingApplicationContextInitializer,\
org.springframework.boot.context.embedded.ServerPortInfoApplicationContextInitializer