Playground for spring boot configuration override mechanism

Spring boot applications can be easily configured in a file classpath:/application.yml. Such a file ships a set of default configuration items. An additional override file can be specified on the command line --spring.config.location=classpath:/override.yml. That is easy so far but it becomes more interesting with spring profiles.

A additional spring profile can be activated by adding it to spring.profiles.include or spring.profiles.active in application.yml. Let’s assume an additional profile extra is active. Spring boot will automatically read the file classpath:/application-extra.yml which can contain additional config items. But the override file override.yml will not override the configuration found in application-extra.yml. There are 2 solutions.

1. Use the multidocument feature of YAML in override.yml such as.

   mainkey: mainoverridevalue
   ---
   spring:
     profiles: extra
   extrakey: extraoverridevalue

   The mainkey item will override the default profile and the extrakey item will override the extra profile.

2. Use two override files like --spring.config.location=classpath:/override.yml,classpath:/override-extra.yml. Make sure that the override-extra.yml starts like:

   spring:
     profiles: extra
   extrakey: extraoverridevalue