Add ComponentScan aliases on SpringBootApplication

Add aliases for `@ComponentScan`attributes on `@SpringBootApplication`
so that it is possible to customize how the component scan should be
applied on the project.

Previously, one would have to revert to `@EnableAutoConfiguration` to
achieve the same result.

Closes gh-3368

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/SpringBootApplication.java

@@ -26,6 +26,7 @@ import java.lang.annotation.Target;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.AliasFor;
 
 /**
  * Indicates a {@link Configuration configuration} class that declares one or more
@@ -61,4 +62,25 @@ public @interface SpringBootApplication {
 	 */
 	String[] excludeName() default {};
 
+	/**
+	 * Base packages to scan for annotated components.
+	 * <p>Use {@link #scanBasePackageClasses} for a type-safe alternative to
+	 * String-based package names.
+	 * @return base packages to scan
+	 * @since 1.3.0
+	 */
+	@AliasFor(annotation = ComponentScan.class, attribute = "basePackages")
+	String[] scanBasePackages() default {};
+
+	/**
+	 * Type-safe alternative to {@link #scanBasePackages} for specifying the packages
+	 * to scan for annotated components. The package of each class specified will be scanned.
+	 * <p>Consider creating a special no-op marker class or interface in each package
+	 * that serves no purpose other than being referenced by this attribute.
+	 * @return base packages to scan
+	 * @since 1.3.0
+	 */
+	@AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses")
+	Class<?>[] scanBasePackageClasses() default {};
+
 }

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

@@ -696,6 +696,9 @@ The `@SpringBootApplication` annotation is equivalent to using `@Configuration`,
 	}
 ----
 
+NOTE: `@SpringBootApplication` also provides aliases to customize the attributes of
+`@EnableAutoConfiguration` and `@ComponentScan`.
+
 
 
 [[using-boot-running-your-application]]