Support searches for non-public repeatable annotations

Prior to this commit, searches for non-public repeatable annotations
failed with error messages similar to the following, since the
repeatable annotation's container's `value()` method could not be
invoked via reflection.

JDK 8:

java.lang.IllegalAccessError: tried to access class
org.springframework.core.annotation.NestedRepeatableAnnotationsTests$A
from class com.sun.proxy.$Proxy12

JDK 17:

java.lang.IllegalAccessError: failed to access class
org.springframework.core.annotation.NestedRepeatableAnnotationsTests$A
from class jdk.proxy2.$Proxy12
(org.springframework.core.annotation.NestedRepeatableAnnotationsTests$A
is in unnamed module of loader 'app'; jdk.proxy2.$Proxy12 is in module
jdk.proxy2 of loader 'app')

This commit makes it possible to search for non-public repeatable
annotations by first attempting to invoke the repeatable annotation's
container's `value()` method via the container's InvocationHandler (if
the container is a JDK dynamic proxy) and then falling back to
reflection for the method invocation if an error occurs (such as a
SecurityException).

Closes gh-29301

spring-core/src/main/java/org/springframework/core/annotation/RepeatableContainers.java

@@ -18,7 +18,9 @@
 
 import java.lang.annotation.Annotation;
 import java.lang.annotation.Repeatable;
+import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
 import java.util.Map;
 
 import org.springframework.lang.Nullable;
@@ -131,6 +133,19 @@ public static RepeatableContainers none() {
 		return NoRepeatableContainers.INSTANCE;
 	}
 
+	private static Object invokeAnnotationMethod(Annotation annotation, Method method) {
+		if (Proxy.isProxyClass(annotation.getClass())) {
+			try {
+				InvocationHandler handler = Proxy.getInvocationHandler(annotation);
+				return handler.invoke(annotation, method, null);
+			}
+			catch (Throwable ex) {
+				// ignore and fall back to reflection below
+			}
+		}
+		return ReflectionUtils.invokeMethod(method, annotation);
+	}
+
 
 	/**
 	 * Standard {@link RepeatableContainers} implementation that searches using
@@ -153,7 +168,7 @@ private static class StandardRepeatableContainers extends RepeatableContainers {
 		Annotation[] findRepeatedAnnotations(Annotation annotation) {
 			Method method = getRepeatedAnnotationsMethod(annotation.annotationType());
 			if (method != null) {
-				return (Annotation[]) ReflectionUtils.invokeMethod(method, annotation);
+				return (Annotation[]) invokeAnnotationMethod(annotation, method);
 			}
 			return super.findRepeatedAnnotations(annotation);
 		}
@@ -240,7 +255,7 @@ private Class<? extends Annotation> deduceContainer(Class<? extends Annotation>
 		@Nullable
 		Annotation[] findRepeatedAnnotations(Annotation annotation) {
 			if (this.container.isAssignableFrom(annotation.annotationType())) {
-				return (Annotation[]) ReflectionUtils.invokeMethod(this.valueMethod, annotation);
+				return (Annotation[]) invokeAnnotationMethod(annotation, this.valueMethod);
 			}
 			return super.findRepeatedAnnotations(annotation);
 		}

spring-core/src/test/java/org/springframework/core/annotation/NestedRepeatableAnnotationsTests.java

@@ -181,7 +181,7 @@ void annotatedMethod() {
 	@Retention(RetentionPolicy.RUNTIME)
 	@Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
 	@Repeatable(A.Container.class)
-	public @interface A {
+	@interface A {
 
 		int value() default 0;
 
@@ -197,7 +197,7 @@ void annotatedMethod() {
 	@Repeatable(B.Container.class)
 	@A
 	@A
-	public @interface B {
+	@interface B {
 
 		@AliasFor(annotation = A.class)
 		int value();