Use Summon in springboot application to fetch secrets via a command in docker and inject it as environment variable

Question

I have a spring boot application and I have stored the secrets in Vault (a secrets management platform). and im using Summon for fetching secrets. the application is dockerized, and in the docker file I specified a Summon command to fetch the secrets and inject them as environment variable inside of the application.yml properties.

CMD summon -f secrets.yml -e ${APP_RUN_PROFILE} java -jar ssc-main.jar \
    --spring.profiles.active=$APP_RUN_PROFILE \
    $EXTRA_JAVA_OPTIONS

• in my secrets.yml file I have the path to the secrets.
• in the application.yml I used

cfg.app.token.smth.username="#{environment.SMTH_USERNAME_SECRET}"

My questions are:

• Is this environment variable injected after the application has started?
• Since, the the properties are loaded during the application startup, does it still load the application with empty values and then inject those variables after the application has started?
• Is it a correct way of injecting those secrets?