spring配置文件加载顺序

首先config中的优先级高于config外resource下的，也就是在environment中的PropertySource元素排在前面。

而在springboot项目中，加载application文件，在springcloud项目中，application和bootstrap都可以加载，但是application的优先级更高。

在springcloud项目中，配置项应放置在bootstrap文件中。

/**
 * A listener that prepares a SpringApplication (e.g. populating its Environment) by
 * delegating to {@link ApplicationContextInitializer} beans in a separate bootstrap
 * context. The bootstrap context is a SpringApplication created from sources defined in
 * spring.factories as {@link BootstrapConfiguration}, and initialized with external
 * config taken from "bootstrap.properties" (or yml), instead of the normal
 * "application.properties".
 *
 * @author Dave Syer
 *
 */
public class BootstrapApplicationListener
    implements ApplicationListener<ApplicationEnvironmentPreparedEvent>, Ordered {
}