Using Gradle property expansion in kotlin/spring boot - spring-boot

Question

I am currently building a Kotlin, Spring Boot service using gradle as the build tool. I am attempting to automatically expand properties found in my application.properties file, using the steps found here:
https://docs.spring.io/spring-boot/docs/current/reference/html/howto-properties-and-configuration.html#howto-automatic-expansion-gradle
My versions are as follows:
- kotlin: 1.1.4-3
- spring boot: 1.5.6.RELEASE
- gradle: 3.5.1
When I run a ./gradlew bootRun, I get the following error:
java.lang.IllegalArgumentException: Could not resolve placeholder 'myServiceName' in value "${myServiceName}"
Followed by:
java.lang.IllegalStateException: LifecycleProcessor not initialized - call 'refresh' before invoking lifecycle methods via the context: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext#510aeb93: startup date [Fri Sep 15 10:59:51 AEST 2017]; parent: org.springframework.context.annotation.AnnotationConfigApplicationContext#68edf5bb
build.gradle:
apply plugin: 'kotlin'
apply plugin: 'kotlin-spring'
apply plugin: 'org.springframework.boot'
processResources {
filesMatching('application.properties') {
expand(project.properties)
}
}
gradle.properties:
myServiceName=potato-service
application.properties:
info.app.name=${myServiceName}
These errors appear after the app has started, and spring is trying to load the property file.
The interesting thing is that if I change the variable that I am trying to substitute in the application.properties, to myServiceName123 for example, gradle fails at the processResources stage.

Answer 1

So, there was a small part of my build.gradle that I did not include above as I did not know about it:
bootRun {
addResources = true
}
According to the Spring Boot Docs having the addResources flag set to true will ignore the application.properties file created in the processResources step, and instead use the one in your projects sources. This is to allow you to dynamically change the file without needing to restart the application.
The correct fix for this (if you need variable expansion when running with the bootRun task) is to set:
bootRun {
addResources = false
}
Otherwise, if you just need expansion when building your jar, leaving this flag as true should be fine.