Cloud Run, Secret Manager and Spring Boot - spring-boot

Question

I want to load whole .properties file from GCP Secret Manager to my Spring Boot application.
Secret is "mounted as volume" in Cloud Run (whole .properties file, in path /secrets/secret.properties), but I cannot manage to load it to Spring Boot using spring.config.import
I was trying:
spring.config.import=optional:configtree:/secrets/
spring.config.import=optional:classpath:/secrets/secret.properties
spring.config.import=optional:/secrets/secret.properties
but nothing works. Values are not visible in Spring Boot application.
(java.lang.IllegalArgumentException: Could not resolve placeholder 'x' in value "${x}")
When putting file on resource classpath, everything works.

Answer 1

Here the set up that I have tested and which works (don't forget to grant the correct permissions)
JIB configuration
...
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>com.google.cloud.tools</groupId>
<artifactId>jib-maven-plugin</artifactId>
<version>3.1.1</version>
<configuration>
<container>
<args>--spring.config.location=file:///secret/my.properties</args>
</container>
<to>
<image>gcr.io/<PROJECT_ID>/springboot</image>
<credHelper>gcr</credHelper>
</to>
</configuration>
</plugin>
...
My Cloud Run deployment
gcloud beta run deploy --image=gcr.io/<PROJECT_ID>/springboot \
--region=us-central1 --allow-unauthenticated --platform=managed \
--set-secrets=/secret/my.properties=projects/<PROJECT_Number>/secrets/springboot:1 \
secret-springboot