Configuration Metadata
Spring Boot jar 包含了元数据文件，其中提供了所有受支持的配置属性的详细信息。这些文件旨在让 IDE 开发人员在用户使用 application.properties 或 application.yaml 文件时提供上下文帮助和 “code completion”。
Spring Boot jars include metadata files that provide details of all supported configuration properties.
The files are designed to let IDE developers offer contextual help and “code completion” as users are working with application.properties or application.yaml files.
编译时，系统会通过处理使用 @ConfigurationProperties 注解的所有项自动生成大多数元数据文件。但是，对于特殊情况或更高级的用例，可以 write part of the metadata manually。
The majority of the metadata file is generated automatically at compile time by processing all items annotated with @ConfigurationProperties.
However, it is possible to write part of the metadata manually for corner cases or more advanced use cases.