Add relative ordering to @autoConfiguration

The relative ordering is implemented with @AliasFor annotations on the
@autoConfiguration annotation. The production code already works without
changes, only the test code had to be modified. It now uses
AnnotationMetadata which already knows how to deal with @AliasFor
instead of using the reflection API directly.

See gh-29907

Author: mhalbritter

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

@@ -25,8 +25,11 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.context.annotation.ImportCandidates;
+import org.springframework.context.annotation.AnnotationBeanNameGenerator;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.AliasFor;
 import org.springframework.core.io.support.SpringFactoriesLoader;
 
 /**
@@ -55,6 +58,52 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 @Configuration(proxyBeanMethods = false)
+@AutoConfigureBefore
+@AutoConfigureAfter
 public @interface AutoConfiguration {
 
+	/**
+	 * Explicitly specify the name of the Spring bean definition associated with the
+	 * {@code @AutoConfiguration} class. If left unspecified (the common case), a bean
+	 * name will be automatically generated.
+	 * <p>
+	 * The custom name applies only if the {@code @AutoConfiguration} class is picked up
+	 * via component scanning or supplied directly to an
+	 * {@link AnnotationConfigApplicationContext}. If the {@code @AutoConfiguration} class
+	 * is registered as a traditional XML bean definition, the name/id of the bean element
+	 * will take precedence.
+	 * @return the explicit component name, if any (or empty String otherwise)
+	 * @see AnnotationBeanNameGenerator
+	 */
+	@AliasFor(annotation = Configuration.class)
+	String value() default "";
+
+	/**
+	 * The auto-configure classes that should have not yet been applied.
+	 * @return the classes
+	 */
+	@AliasFor(annotation = AutoConfigureBefore.class, attribute = "value")
+	Class<?>[] before() default {};
+
+	/**
+	 * The names of the auto-configure classes that should have not yet been applied.
+	 * @return the class names
+	 */
+	@AliasFor(annotation = AutoConfigureBefore.class, attribute = "name")
+	String[] beforeName() default {};
+
+	/**
+	 * The auto-configure classes that should have already been applied.
+	 * @return the classes
+	 */
+	@AliasFor(annotation = AutoConfigureAfter.class, attribute = "value")
+	Class<?>[] after() default {};
+
+	/**
+	 * The names of the auto-configure classes that should have already been applied.
+	 * @return the class names
+	 */
+	@AliasFor(annotation = AutoConfigureAfter.class, attribute = "name")
+	String[] afterName() default {};
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,13 +21,15 @@
 import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.Ordered;
+import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
@@ -43,6 +45,7 @@
  *
  * @author Phillip Webb
  * @author Andy Wilkinson
+ * @author Moritz Halbritter
  */
 class AutoConfigurationSorterTests {
 
@@ -54,8 +57,14 @@ class AutoConfigurationSorterTests {
 
 	private static final String A = AutoConfigureA.class.getName();
 
+	private static final String A2 = AutoConfigureA2.class.getName();
+
+	private static final String A3 = AutoConfigureA3.class.getName();
+
 	private static final String B = AutoConfigureB.class.getName();
 
+	private static final String B2 = AutoConfigureB2.class.getName();
+
 	private static final String C = AutoConfigureC.class.getName();
 
 	private static final String D = AutoConfigureD.class.getName();
@@ -64,15 +73,17 @@ class AutoConfigurationSorterTests {
 
 	private static final String W = AutoConfigureW.class.getName();
 
+	private static final String W2 = AutoConfigureW2.class.getName();
+
 	private static final String X = AutoConfigureX.class.getName();
 
 	private static final String Y = AutoConfigureY.class.getName();
 
+	private static final String Y2 = AutoConfigureY2.class.getName();
+
 	private static final String Z = AutoConfigureZ.class.getName();
 
-	private static final String A2 = AutoConfigureA2.class.getName();
-
-	private static final String W2 = AutoConfigureW2.class.getName();
+	private static final String Z2 = AutoConfigureZ2.class.getName();
 
 	private AutoConfigurationSorter sorter;
 
@@ -95,12 +106,24 @@ void byAutoConfigureAfter() {
 		assertThat(actual).containsExactly(C, B, A);
 	}
 
+	@Test
+	void byAutoConfigureAfterAliasFor() {
+		List<String> actual = this.sorter.getInPriorityOrder(Arrays.asList(A3, B2, C));
+		assertThat(actual).containsExactly(C, B2, A3);
+	}
+
 	@Test
 	void byAutoConfigureBefore() {
 		List<String> actual = this.sorter.getInPriorityOrder(Arrays.asList(X, Y, Z));
 		assertThat(actual).containsExactly(Z, Y, X);
 	}
 
+	@Test
+	void byAutoConfigureBeforeAliasFor() {
+		List<String> actual = this.sorter.getInPriorityOrder(Arrays.asList(X, Y2, Z2));
+		assertThat(actual).containsExactly(Z2, Y2, X);
+	}
+
 	@Test
 	void byAutoConfigureAfterDoubles() {
 		List<String> actual = this.sorter.getInPriorityOrder(Arrays.asList(A, B, C, E));
@@ -170,29 +193,47 @@ private AutoConfigurationMetadata getAutoConfigurationMetadata(String... classNa
 		for (String className : classNames) {
 			Class<?> type = ClassUtils.forName(className, null);
 			properties.put(type.getName(), "");
-			AutoConfigureOrder order = type.getDeclaredAnnotation(AutoConfigureOrder.class);
+			AnnotationMetadata annotationMetadata = AnnotationMetadata.introspect(type);
+			addAutoConfigureOrder(properties, className, annotationMetadata);
+			addAutoConfigureBefore(properties, className, annotationMetadata);
+			addAutoConfigureAfter(properties, className, annotationMetadata);
+		}
+		return AutoConfigurationMetadataLoader.loadMetadata(properties);
+	}
+
+	private void addAutoConfigureAfter(Properties properties, String className, AnnotationMetadata annotationMetadata) {
+		Map<String, Object> autoConfigureAfter = annotationMetadata
+				.getAnnotationAttributes(AutoConfigureAfter.class.getName(), true);
+		if (autoConfigureAfter != null) {
+			properties.put(className + ".AutoConfigureAfter",
+					merge((String[]) autoConfigureAfter.get("value"), (String[]) autoConfigureAfter.get("name")));
+		}
+	}
+
+	private void addAutoConfigureBefore(Properties properties, String className,
+			AnnotationMetadata annotationMetadata) {
+		Map<String, Object> autoConfigureBefore = annotationMetadata
+				.getAnnotationAttributes(AutoConfigureBefore.class.getName(), true);
+		if (autoConfigureBefore != null) {
+			properties.put(className + ".AutoConfigureBefore",
+					merge((String[]) autoConfigureBefore.get("value"), (String[]) autoConfigureBefore.get("name")));
+		}
+	}
+
+	private void addAutoConfigureOrder(Properties properties, String className, AnnotationMetadata annotationMetadata) {
+		Map<String, Object> autoConfigureOrder = annotationMetadata
+				.getAnnotationAttributes(AutoConfigureOrder.class.getName());
+		if (autoConfigureOrder != null) {
+			Integer order = (Integer) autoConfigureOrder.get("order");
 			if (order != null) {
-				properties.put(className + ".AutoConfigureOrder", String.valueOf(order.value()));
-			}
-			AutoConfigureBefore autoConfigureBefore = type.getDeclaredAnnotation(AutoConfigureBefore.class);
-			if (autoConfigureBefore != null) {
-				properties.put(className + ".AutoConfigureBefore",
-						merge(autoConfigureBefore.value(), autoConfigureBefore.name()));
-			}
-			AutoConfigureAfter autoConfigureAfter = type.getDeclaredAnnotation(AutoConfigureAfter.class);
-			if (autoConfigureAfter != null) {
-				properties.put(className + ".AutoConfigureAfter",
-						merge(autoConfigureAfter.value(), autoConfigureAfter.name()));
+				properties.put(className + ".AutoConfigureOrder", String.valueOf(order));
 			}
 		}
-		return AutoConfigurationMetadataLoader.loadMetadata(properties);
 	}
 
-	private String merge(Class<?>[] value, String[] name) {
+	private String merge(String[] value, String[] name) {
 		Set<String> items = new LinkedHashSet<>();
-		for (Class<?> type : value) {
-			items.add(type.getName());
-		}
+		Collections.addAll(items, value);
 		Collections.addAll(items, name);
 		return StringUtils.collectionToCommaDelimitedString(items);
 	}
@@ -222,11 +263,21 @@ static class AutoConfigureA2 {
 
 	}
 
+	@AutoConfiguration(after = AutoConfigureB2.class)
+	static class AutoConfigureA3 {
+
+	}
+
 	@AutoConfigureAfter({ AutoConfigureC.class, AutoConfigureD.class, AutoConfigureE.class })
 	static class AutoConfigureB {
 
 	}
 
+	@AutoConfiguration(after = { AutoConfigureC.class, AutoConfigureD.class, AutoConfigureE.class })
+	static class AutoConfigureB2 {
+
+	}
+
 	static class AutoConfigureC {
 
 	}
@@ -259,11 +310,21 @@ static class AutoConfigureY {
 
 	}
 
+	@AutoConfiguration(before = AutoConfigureX.class)
+	static class AutoConfigureY2 {
+
+	}
+
 	@AutoConfigureBefore(AutoConfigureY.class)
 	static class AutoConfigureZ {
 
 	}
 
+	@AutoConfiguration(before = AutoConfigureY2.class)
+	static class AutoConfigureZ2 {
+
+	}
+
 	static class SkipCycleMetadataReaderFactory extends CachingMetadataReaderFactory {
 
 		@Override