SpringBoot 配置文件无法解析占位符 - ${value} - 简书
https://www.jianshu.com/p/b4221ca6300f
深入Spring Boot：那些注入不了的Spring占位符（${}表达式）_横云断岭的专栏-CSDN博客
https://blog.csdn.net/hengyunabc/article/details/75453307
深入Spring Boot：那些注入不了的Spring占位符（${}表达式） | 横云断岭的专栏
http://hengyunabc.github.io/spring-placeholder-inject-failed-cases/