How to specify a profile when deploying a Spring boot war file to Tomcat?

Well, I've found a way to do that. In the conf directory of Tomcat, add this line to the file catalina.properties there.

spring.profiles.active=<YOUR_PROFILE>

Replace <YOUR_PROFILE> here of course with your profile's name. For example if you are using application-TEST.properties, it would be the following.

spring.profiles.active=TEST