Document @SpringBootApplication

Add a section to the reference guide about @SpringBootApplication.

See gh-1842

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -1442,7 +1442,7 @@ and  http://hibernate.org/orm/documentation/[Hibernate] reference documentation.
 Traditionally, JPA '`Entity`' classes are specified in a `persistence.xml` file. With
 Spring Boot this file is not necessary and instead '`Entity Scanning`' is used. By
 default all packages below your main configuration class (the one annotated with
-`@EnableAutoConfiguration`) will be searched.
+`@EnableAutoConfiguration` or `@SpringBootApplication`) will be searched.
 
 Any classes annotated with `@Entity`, `@Embeddable` or `@MappedSuperclass` will be
 considered. A typical entity class would look something like this:
@@ -1511,7 +1511,8 @@ Spring Data repositories usually extend from the
 {spring-data-commons-javadoc}/repository/Repository.html[`Repository`] or
 {spring-data-commons-javadoc}/repository/CrudRepository.html[`CrudRepository`] interfaces. If you are using
 auto-configuration, repositories will be searched from the package containing your
-main configuration class (the one annotated with `@EnableAutoConfiguration`) down.
+main configuration class (the one annotated with `@EnableAutoConfiguration` or
+`@SpringBootApplication`) down.
 
 Here is a typical Spring Data repository:
 

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -550,6 +550,36 @@ 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 <<using-boot-structuring-your-code, best practices>>
+above), Spring Boot provides a convenient `@SpringBootApplication` alternative.
+
+The `@SpringBootApplication` annotation is equivalent to using `@Configuration`,
+`@EnableAutoConfiguration` and `@ComponentScan` with their default attributes:
+
+
+[source,java,indent=0]
+----
+	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);
+		}
+
+	}
+----
+
+
+
 [[using-boot-running-your-application]]
 == Running your application
 One of the biggest advantages of packaging your application as jar and using an embedded