What is the role of the ComponentScan annotation in Spring application configuration?

The @ComponentScan annotation in Spring indicates to the framework which packages to scan for classes annotated with component annotations (@Component, @Service, @Repository, @Controller, etc.) in order to automatically register them as beans in the application context.

Without @ComponentScan, Spring will not know where to look for these classes, and they will not be created and injected automatically.

Example of usage:

@Configuration
@ComponentScan(basePackages = "com.example.app")
public class AppConfig {
    // Spring configuration
}

Here, Spring will scan the com.example.app package and its subpackages for components.