# Profiles and External Configuration — Spring Boot

Source: https://www.skillbyai.com/en/spring-boot/o-profiles

> One artifact, many environments.

## application-{profile}.properties and precedence

Activate **profiles** (`dev`, `test`, `prod`) with `spring.profiles.active` to load `application-prod.properties` on top of the defaults. Configuration sources have a defined precedence: command-line arguments and environment variables override files packaged in the jar. Keep secrets out of the repository: inject them through environment variables or a secret store (Vault, cloud secret managers) at runtime. Build one artifact and configure it per environment.

## Profile-specific settings

Not part of the built demo; check the Spring documentation for your version.

```properties
# application-prod.properties
spring.datasource.url=jdbc:postgresql://db.internal:5432/shop
spring.datasource.username=shop_app
# password comes from the environment: SPRING_DATASOURCE_PASSWORD
spring.jpa.hibernate.ddl-auto=validate
management.server.port=9090
logging.level.root=INFO

# run with:  java -jar shop.jar --spring.profiles.active=prod
```

## Same jar everywhere

Rebuilding per environment hides differences; promote one tested artifact and change only configuration.

**Quiz:** Which overrides a value in application.properties inside the jar?

- [x] An environment variable or command-line argument
- [ ] A comment in the code
- [ ] The jar file name
- [ ] Nothing can override it

*Answer:* An environment variable or command-line argument. External configuration wins.