获取监听器

SpringApplicationRunListeners listeners = getRunListeners(args); 跟进getRunListeners方法：

private SpringApplicationRunListeners getRunListeners(String[] args) {    Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };    return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances(            SpringApplicationRunListener.class, types, this, args));}