Spring Boot 笔记 - 注解(四)-- @SpringBootApplication

本是古典何须时尚 2022-02-26 01:20 250阅读 0赞

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][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, as shown in the following example:

package com.example.myapplication;
    
    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);
    	}
    
    }

![20190328165152705.png][]

package com.example.myapplication;
    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)

[Spring Boot_s auto-configuration mechanism]: https://docs.spring.io/spring-boot/docs/2.0.8.RELEASE/reference/htmlsingle/#using-boot-auto-configuration
[the best practices]: https://docs.spring.io/spring-boot/docs/2.0.8.RELEASE/reference/htmlsingle/#using-boot-structuring-your-code
[20190328165152705.png]: /images/20220226/91ff3f22d7d04696825240aba5dc6ea6.png