SpringBoot引用外部配置文件

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参考文献：

https://www.cnblogs.com/xiaoqi/p/6955288.html

https://blog.csdn.net/qq_35981283/article/details/77583073

https://blog.csdn.net/lyf_ldh/article/details/81182497

https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html