M01 Q24 What is @Profile annotation?

How do you configure profiles?

Spring Profiles are configured by:

Specifying which beans are part of which profile
Specifying which profiles are active

You can specify beans being part of the profile in the following ways:

Use @Profile annotation at @Component class level – bean will be part of profile/profiles specified in the annotation

Use @Profile annotation at @Configuration class level – all beans from this configuration will be part of profile/profiles specified in the annotation

Use @Profile annotation at @Bean method of @Configuration class – an instance of bean returned by this method will be part of profile/profiles specified in the annotation

Use @Profile annotation to define custom annotation - @Component / @Configuration / @Bean method annotated with custom annotation will be part of profile/profiles specified in the annotation

If Bean does not have profile specified in any way, it will be created in every profile. You can use ! to specify which profile bean should not be created.

How to activate profile?

You can activate profiles in the following way:

Programmatically with the usage of ConfigurableEnvironment

By using spring.profiles.active property

On JUnit Test level by using @ActiveProfiles annotation

In Spring Boot Programmatically by the usage of SpringApplicationBuilder

In Spring Boot by application.properties or in YML-file

What are possible use cases where they might be useful?

Spring Profiles are useful in the following cases:

Changing Behavior of the system in Different Environments by changing set of Beans that are part of specific environments, for example, prod, cert, dev
Changing Behavior of the system for different customers
Changing set of Beans used in Development Environment and also during Testing Execution
Changing set of Beans in the system when monitoring or additional debugging capabilities should be turned on