18. Using the @SpringBootApplication annotation

18. Using the @SpringBootApplication annotation
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Many Spring Boot developers like their apps to use auto-configuration, component scan and be able to define extra configuration on their "application class". A single @SpringBootApplication annotation can be used to enable those three features, that is:

@EnableAutoConfiguration: enable Spring Boot’s auto-configuration mechanism
@ComponentScan: enable @Component scan on the package where the application is located (see the best practices)
@Configuration: allow to register extra beans in the context or import additional configuration classes

The @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration and @ComponentScan with their default attributes:

package com.example.myproject;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication // same as @Configuration @EnableAutoConfiguration @ComponentScan
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

	Note
	`@SpringBootApplication` also provides aliases to customize the attributes of `@EnableAutoConfiguration` and `@ComponentScan`.

Note

None of these features are mandatory and you may chose to replace this single annotation by any of the features that it enables. For instance, you may not want to use component scan in your application:

package com.example.myproject;

import org.springframework.boot.SpringApplication;
import org.springframework.context.annotation.ComponentScan
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;

@Configuration
@EnableAutoConfiguration
@Import({ MyConfig.class, MyAnotherConfig.class })
public class Application {

    public static void main(String[] args) {
            SpringApplication.run(Application.class, args);
    }

}

In this example, Application is just like any other Spring Boot application except that @Component-annotated classes are not detected automatically and the user-defined beans are imported explicitly (see @Import).

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