Externalize properties for command line tool using spring boot - spring-boot

Question

I wanted to do a very simple thing which I had already done, which is using a spring boot packaged jar with some custom properties (private.properties containing a token) provided in a "config" directory. Currently I'm using a recent version of Spring Boot ("2.2.5.RELEASE").
My "config" directory was never taken into account and I had to do 2 very unintuitive things :
Complete spring boot maven plugin conf like this :
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<mainClass>${start-class}</mainClass>
<layout>ZIP</layout>
</configuration>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
and add these properties :
java -Dloader.home=. -Dloader.path=config -Dloader.config.name=private -jar my.jar
Could someone please tell me where is it officially documented (both actions) ? Is there a more simple way of doing this with less explicit parameters ?

Answer 1

Here is the answer :
"ZIP (alias to DIR): similar to the JAR layout using PropertiesLauncher."
source : https://docs.spring.io/spring-boot/docs/current/maven-plugin/reference/html/#repackage
and :
"PropertiesLauncher is a launcher for archives with user-configured classpath and main class via a properties file. This model is often more flexible and more amenable to creating well-behaved OS-level services than a model based on executable jars.
Looks in various places for a properties file to extract loader settings, defaulting to loader.properties either on the current classpath or in the current working directory. The name of the properties file can be changed by setting a System property loader.config.name (e.g. -Dloader.config.name=foo will look for foo.properties. If that file doesn't exist then tries loader.config.location (with allowed prefixes classpath: and file: or any valid URL). Once that file is located turns it into Properties and extracts optional values (which can also be provided overridden as System properties in case the file doesn't exist):
loader.path: a comma-separated list of directories (containing file resources and/or nested archives in *.jar or *.zip or archives) or archives to append to the classpath. BOOT-INF/classes,BOOT-INF/lib in the application archive are always used
loader.main: the main method to delegate execution to once the class loader is set up. No default, but will fall back to looking for a Start-Class in a MANIFEST.MF, if there is one in ${loader.home}/META-INF.
"
source : https://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/loader/PropertiesLauncher.html