Add ComponentScan#nameGenerator alias on @SpringBootApplication

This commit allows to customize the default BeanNameGenerator for
scanned components using @SpringBootApplication.

Closes gh-19346

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

@@ -23,8 +23,11 @@
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import org.springframework.beans.factory.support.BeanNameGenerator;
+import org.springframework.boot.SpringApplication;
 import org.springframework.boot.SpringBootConfiguration;
 import org.springframework.boot.context.TypeExcludeFilter;
+import org.springframework.context.annotation.AnnotationBeanNameGenerator;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.ComponentScan.Filter;
@@ -104,6 +107,22 @@
 	@AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses")
 	Class<?>[] scanBasePackageClasses() default {};
 
+	/**
+	 * The {@link BeanNameGenerator} class to be used for naming detected components
+	 * within the Spring container.
+	 * <p>
+	 * The default value of the {@link BeanNameGenerator} interface itself indicates that
+	 * the scanner used to process this {@code @SpringBootApplication} annotation should
+	 * use its inherited bean name generator, e.g. the default
+	 * {@link AnnotationBeanNameGenerator} or any custom instance supplied to the
+	 * application context at bootstrap time.
+	 * @return {@link BeanNameGenerator} to use
+	 * @see SpringApplication#setBeanNameGenerator(BeanNameGenerator)
+	 * @since 2.3.0
+	 */
+	@AliasFor(annotation = ComponentScan.class, attribute = "nameGenerator")
+	Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
+
 	/**
 	 * Specify whether {@link Bean @Bean} methods should get proxied in order to enforce
 	 * bean lifecycle behavior, e.g. to return shared singleton bean instances even in

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/SpringBootApplicationTests.java

@@ -18,6 +18,9 @@
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.beans.factory.support.BeanNameGenerator;
+import org.springframework.beans.factory.support.DefaultBeanNameGenerator;
+import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.core.annotation.AnnotationAttributes;
@@ -28,6 +31,7 @@
  * Tests for {@link SpringBootApplication @SpringBootApplication}.
  *
  * @author Andy Wilkinson
+ * @author Stephane Nicoll
  */
 class SpringBootApplicationTests {
 
@@ -45,6 +49,20 @@ void proxyBeanMethodsCanBeDisabled() {
 		assertThat(attributes.get("proxyBeanMethods")).isEqualTo(false);
 	}
 
+	@Test
+	void nameGeneratorDefaultToBeanNameGenerator() {
+		AnnotationAttributes attributes = AnnotatedElementUtils
+				.getMergedAnnotationAttributes(DefaultSpringBootApplication.class, ComponentScan.class);
+		assertThat(attributes.get("nameGenerator")).isEqualTo(BeanNameGenerator.class);
+	}
+
+	@Test
+	void nameGeneratorCanBeSpecified() {
+		AnnotationAttributes attributes = AnnotatedElementUtils
+				.getMergedAnnotationAttributes(CustomNameGeneratorConfiguration.class, ComponentScan.class);
+		assertThat(attributes.get("nameGenerator")).isEqualTo(TestBeanNameGenerator.class);
+	}
+
 	@SpringBootApplication
 	static class DefaultSpringBootApplication {
 
@@ -55,4 +73,13 @@ static class NoBeanMethodProxyingSpringBootApplication {
 
 	}
 
+	@SpringBootApplication(nameGenerator = TestBeanNameGenerator.class)
+	static class CustomNameGeneratorConfiguration {
+
+	}
+
+	static class TestBeanNameGenerator extends DefaultBeanNameGenerator {
+
+	}
+
 }