资源文件默认使用${...}为占位符，但如果pom继承了 spring-boot-starter-parent，那么默认占位符就改为了 @...@
例如：
#application.yml
spring:
profiles:
active: @profiles.active@
# pom.xml
<project>
...
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.5.3</version>
<relativePath/>
</parent>
<profiles>
<profile>
<id>dev</id>
<properties>
<profiles.active>dev</profiles.active>
</properties>
<activation>
<activeByDefault>true</activeByDefault>
</activation>
</profile>
<profile>
<id>prod</id>
<properties>
<profiles.active>prod</profiles.active>
</properties>
</profile>
</profiles>
<build>
<finalName>Example</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>false</filtering>
<excludes>
<exclude>application*.yml</exclude>
<exclude>config/**</exclude>
</excludes>
<includes>
<include>**/*</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
<includes>
<include>application.yml</include>
<include>application-${profiles.active}.yml</include>
<include>config/${profiles.active}/*</include>
</includes>
</resource>
</resources>
</build>
</project>
另外注意一点，Intellij IDEA运行Springboot项目时，默认会使用内置的编译器，不去执行maven中的编译配置。这将导致maven build正常，但run/debug报错，报错信息如下：
org.yaml.snakeyaml.scanner.ScannerException: while scanning for the next token
found character '@' that cannot start any token. (Do not use @ for indentation)
in 'reader', line 11, column 15:
active: @profiles.active@
^
这个问题可以通过启用IDEA的Delegate IDE build/run actions to Maven来解决。这个选项为项目级设置，启用后每次编译时将不再使用内置编译，而是调用maven。官方选项说明
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