问题

我需要在Spring Boot的`application.yml`文件中，将map的键设置为占位符，这些占位符引用了一些现有变量（例如环境变量/每个配置文件中声明的变量）。

SETTINGS_ID_1: 1001
SETTINGS_ID_2: 1005

settingsMapping:
    ${SETTINGS_ID_1}: hello
    ${SETTINGS_ID_2}: hi

因此，我期望settingsMapping会有两个键：1001和1005，但实际值是SETTINGS_ID_1和SETTINGS_ID_2。
在application.yml中，Spring是否支持这样的特性呢？这些占位符在map的值中可以正常工作，但在键中却不行。

我尝试了以下选项，但都没有成功（属性要么按原样保留为字符串值，要么抛出异常ParserException: while parsing a flow sequence）：

• [${SETTINGS_ID_2}]
• '[${SETTINGS_ID_2}]'
• $SETTINGS_ID_1
• '$SETTINGS_ID_1'

Spring Boot版本为2.2.2（我猜这与版本无关，但还是提供了版本信息）。

<details>
<summary>英文:</summary>

I need to have placeholders at map&#39;s keys inside Spring Boot `application.yml` that referencing to some existing variables (e.g. env variables / variables declared in props per profile)

   

SETTINGS_ID_1: 1001
SETTINGS_ID_2: 1005

settingsMapping:
${SETTINGS_ID_1}: hello
${SETTINGS_ID_2}: hi


   
So I expect that `settingsMapping` will have two keys: `1001` and `1005`, but real values are `SETTINGS_ID_1` and `SETTINGS_ID_2`.
Does Spring support such feature at `application.yml`? These placeholders work fine in map's values, but not in keys.

I tried the following options but without luck (props either have string values as is it, or exception `ParserException: while parsing a flow sequence`):

    [${SETTINGS_ID_2}]
    '[${SETTINGS_ID_2}]'
    $SETTINGS_ID_1
    '$SETTINGS_ID_1'


spring-boot version `2.2.2` (I guess it does not depend on the version, but anyway provided)


</details>