diff --git a/spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc b/spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc index 46b65c4bf38..0a8b4a13524 100644 --- a/spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc +++ b/spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc @@ -417,14 +417,16 @@ and use a reversed domain name (for example, `com.example.project`). [[using-boot-locating-the-main-class]] === Locating the main application class We generally recommend that you locate your main application class in a root package -above other classes. The `@EnableAutoConfiguration` annotation is often placed on your -main class, and it implicitly defines a base "`search package`" for certain items. For -example, if you are writing a JPA application, the package of the -`@EnableAutoConfiguration` annotated class will be used to search for `@Entity` items. +above other classes. The <> is often placed on your main class, and it +implicitly defines a base "`search package`" for certain items. For example, if you are +writing a JPA application, the package of the `@SpringBootApplication` annotated class +will be used to search for `@Entity` items. Using a root package also allows component +scan to apply only on your project. -Using a root package also allows the `@ComponentScan` annotation to be used without -needing to specify a `basePackage` attribute. You can also use the -`@SpringBootApplication` annotation if your main class is in the root package. +TIP: If you don't want to use `@SpringBootApplication`, the `@EnableAutoConfiguration` +and `@ComponentScan` annotations that it imports defines that behaviour so you can also +use that instead. Here is a typical layout: @@ -447,20 +449,16 @@ Here is a typical layout: ---- The `Application.java` file would declare the `main` method, along with the basic -`@Configuration`. +`@SpringBootApplication`. [source,java,indent=0] ---- package com.example.myproject; import org.springframework.boot.SpringApplication; - import org.springframework.boot.autoconfigure.EnableAutoConfiguration; - import org.springframework.context.annotation.ComponentScan; - import org.springframework.context.annotation.Configuration; + import org.springframework.boot.autoconfigure.SpringBootApplication - @Configuration - @EnableAutoConfiguration - @ComponentScan + @SpringBootApplication public class Application { public static void main(String[] args) { @@ -512,8 +510,9 @@ connection beans, then we will auto-configure an in-memory database. You need to opt-in to auto-configuration by adding the `@EnableAutoConfiguration` or `@SpringBootApplication` annotations to one of your `@Configuration` classes. -TIP: You should only ever add one `@EnableAutoConfiguration` annotation. We generally -recommend that you add it to your primary `@Configuration` class. +TIP: You should only ever add one `@SpringBootApplication` or `@EnableAutoConfiguration` +annotation. We generally recommend that you add one or the other to your primary +`@Configuration` class only. @@ -614,10 +613,16 @@ as `final`, indicating that it cannot be subsequently changed. [[using-boot-using-springbootapplication-annotation]] == Using the @SpringBootApplication annotation -Many Spring Boot developers always have their main class annotated with `@Configuration`, -`@EnableAutoConfiguration` and `@ComponentScan`. Since these annotations are so frequently -used together (especially if you follow the <> -above), Spring Boot provides a convenient `@SpringBootApplication` alternative. +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 tree features, that is: + +* `@EnableAutoConfiguration`: enable <> +* `@ComponentScan`: enable `@Component` scan on the package where the application is +located (see <>) +* `@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: @@ -644,6 +649,39 @@ NOTE: `@SpringBootApplication` also provides aliases to customize the attributes `@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: + +[source,java,indent=0] +---- + 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`). +==== + + [[using-boot-running-your-application]] == Running your application