Using Profiles in Spring Boot

When developping a Spring Boot application, or developping any applicaions, it's offen to follow below process,

Develop in local environment. Mostly may be on Windows
Run some automation test, such as integration test on a testing environment
Deploy to a product environment

In each stage, a separated environment is required, such as,

different database
different server hostname
different Kafka server or topic name

So, we may have define all the configurations in a file, such as application.properties,

Properties

spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.kafka.bootstrap-servers=localhost:9092

And, there also may be some common configurations are applied for all, so how can we use the Spring profile to make easiest work to achieve?

Here is the way,

By default, the Spring boot will try to read condfigurations from file application.properties or application.yml. Let's name it as common profile.
To create a dev profile, simply add new configuration file such as application-dev.properties or application-dev.yml Now, we can put common configurations into the common profile, and put the dev configurations into the dev profile.

And then, the next step is how to let the Spring boot known to use which profile?

There are several ways to do,

Use Profile annotation

In the configuration class, we can define to use which profile.
Java
```
@Configuration
@Profile("dev")
public class ProfileConfiguration {
  ...
}
```
Use environment variable

before start the application, export environment.
Bash
```
export SPRING_PROFILES_ACTIVE=dev
```
On windows,
Bash
```
set SPRING_PROFILES_ACTIVE=dev
```
Use startup argument

Pass in the application arguments. java -jar <application.jar> --spring.profiles.active=dev.

Now, you could create and use multiple profiles in Spring boot.