From 75da9c3c474374289cc128b714126d9d644b69a9 Mon Sep 17 00:00:00 2001
From: Sam Brannen <104798+sbrannen@users.noreply.github.com>
Date: Tue, 12 Dec 2023 18:28:48 +0100
Subject: [PATCH] Scan annotations on method in interface hierarchy only once

Prior to this commit, the AnnotationsScanner used in the
MergedAnnotations infrastructure found duplicate annotations on methods
within multi-level interface hierarchies.

This commit addresses this issue by scanning methods at a given level
in the interface hierarchy using ReflectionUtils#getDeclaredMethods
instead of Class#getMethods, since the latter includes public methods
declared in super-interfaces which will anyway be scanned when
processing super-interfaces recursively.

Closes gh-31803
---
 .../core/annotation/AnnotationsScanner.java   |  5 ++-
 .../annotation/AnnotationsScannerTests.java   | 33 +++++++++++++++++++
 .../annotation/MergedAnnotationsTests.java    | 12 +++++++
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java b/spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java
index a98c005f378..c3f44cc897f 100644
--- a/spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java
+++ b/spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java
@@ -334,11 +334,10 @@ abstract class AnnotationsScanner {
 
 		Method[] methods = baseTypeMethodsCache.get(baseType);
 		if (methods == null) {
-			boolean isInterface = baseType.isInterface();
-			methods = isInterface ? baseType.getMethods() : ReflectionUtils.getDeclaredMethods(baseType);
+			methods = ReflectionUtils.getDeclaredMethods(baseType);
 			int cleared = 0;
 			for (int i = 0; i < methods.length; i++) {
-				if ((!isInterface && Modifier.isPrivate(methods[i].getModifiers())) ||
+				if (Modifier.isPrivate(methods[i].getModifiers()) ||
 						hasPlainJavaAnnotationsOnly(methods[i]) ||
 						getDeclaredAnnotations(methods[i], false).length == 0) {
 					methods[i] = null;
diff --git a/spring-core/src/test/java/org/springframework/core/annotation/AnnotationsScannerTests.java b/spring-core/src/test/java/org/springframework/core/annotation/AnnotationsScannerTests.java
index 66cc1f015b1..6400a880c33 100644
--- a/spring-core/src/test/java/org/springframework/core/annotation/AnnotationsScannerTests.java
+++ b/spring-core/src/test/java/org/springframework/core/annotation/AnnotationsScannerTests.java
@@ -357,6 +357,15 @@ class AnnotationsScannerTests {
 		Method source = methodFrom(WithSingleInterface.class);
 		assertThat(scan(source, SearchStrategy.TYPE_HIERARCHY)).containsExactly(
 				"0:TestAnnotation1", "1:TestAnnotation2", "1:TestInheritedAnnotation2");
+
+		source = methodFrom(Hello1Impl.class);
+		assertThat(scan(source, SearchStrategy.TYPE_HIERARCHY)).containsExactly("1:TestAnnotation1");
+	}
+
+	@Test  // gh-31803
+	void typeHierarchyStrategyOnMethodWhenHasInterfaceHierarchyScansInterfacesOnlyOnce() {
+		Method source = methodFrom(Hello2Impl.class);
+		assertThat(scan(source, SearchStrategy.TYPE_HIERARCHY)).containsExactly("1:TestAnnotation1");
 	}
 
 	@Test
@@ -691,6 +700,30 @@ class AnnotationsScannerTests {
 		}
 	}
 
+	interface Hello1 {
+
+		@TestAnnotation1
+		void method();
+	}
+
+	interface Hello2 extends Hello1 {
+	}
+
+	static class Hello1Impl implements Hello1 {
+
+		@Override
+		public void method() {
+		}
+	}
+
+	static class Hello2Impl implements Hello2 {
+
+		@Override
+		public void method() {
+		}
+	}
+
+
 	@TestAnnotation2
 	@TestInheritedAnnotation2
 	static class HierarchySuperclass extends HierarchySuperSuperclass {
diff --git a/spring-core/src/test/java/org/springframework/core/annotation/MergedAnnotationsTests.java b/spring-core/src/test/java/org/springframework/core/annotation/MergedAnnotationsTests.java
index f7d2389192f..0a2371fa4b1 100644
--- a/spring-core/src/test/java/org/springframework/core/annotation/MergedAnnotationsTests.java
+++ b/spring-core/src/test/java/org/springframework/core/annotation/MergedAnnotationsTests.java
@@ -40,6 +40,8 @@ import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.Ordered;
+import org.springframework.core.annotation.AnnotationsScannerTests.Hello2Impl;
+import org.springframework.core.annotation.AnnotationsScannerTests.TestAnnotation1;
 import org.springframework.core.annotation.MergedAnnotation.Adapt;
 import org.springframework.core.annotation.MergedAnnotations.Search;
 import org.springframework.core.annotation.MergedAnnotations.SearchStrategy;
@@ -686,6 +688,16 @@ class MergedAnnotationsTests {
 		assertThat(annotation.getAggregateIndex()).isEqualTo(1);
 	}
 
+	@Test  // gh-31803
+	void streamWithTypeHierarchyInheritedFromSuperInterfaceMethod() throws Exception {
+		Method method = Hello2Impl.class.getMethod("method");
+		long count = MergedAnnotations.search(SearchStrategy.TYPE_HIERARCHY)
+				.from(method)
+				.stream(TestAnnotation1.class)
+				.count();
+		assertThat(count).isEqualTo(1);
+	}
+
 	@Test
 	void getWithTypeHierarchyInheritedFromAbstractMethod() throws NoSuchMethodException {
 		Method method = ConcreteClassWithInheritedAnnotation.class.getMethod("handle");