Revise getPubliclyAccessibleMethodIfPossible to rely on Module#isExported

This avoids reflection and cache access for regular public and exported types.

Closes gh-35556

Author: jhoeller

spring-core/src/main/java/org/springframework/util/ClassUtils.java

@@ -1483,8 +1483,8 @@ private static Method findInterfaceMethodIfPossible(String methodName, Class<?>[
 	}
 
 	/**
-	 * Get the highest publicly accessible method in the supplied method's type hierarchy that
-	 * has a method signature equivalent to the supplied method, if possible.
+	 * Get the closest publicly accessible (and exported) method in the supplied method's type
+	 * hierarchy that has a method signature equivalent to the supplied method, if possible.
 	 * <p>Otherwise, this method recursively searches the class hierarchy and implemented
 	 * interfaces for an equivalent method that is {@code public} and declared in a
 	 * {@code public} type.
@@ -1507,18 +1507,21 @@ private static Method findInterfaceMethodIfPossible(String methodName, Class<?>[
 	 * @see #getMostSpecificMethod(Method, Class)
 	 */
 	public static Method getPubliclyAccessibleMethodIfPossible(Method method, @Nullable Class<?> targetClass) {
-		// If the method is not public, we can abort the search immediately.
-		if (!Modifier.isPublic(method.getModifiers())) {
+		Class<?> declaringClass = method.getDeclaringClass();
+		// If the method is not public or its declaring class is public and exported already,
+		// we can abort the search immediately (avoiding reflection as well as cache access).
+		if (!Modifier.isPublic(method.getModifiers()) || (Modifier.isPublic(declaringClass.getModifiers()) &&
+				declaringClass.getModule().isExported(declaringClass.getPackageName(), ClassUtils.class.getModule()))) {
 			return method;
 		}
 
 		Method interfaceMethod = getInterfaceMethodIfPossible(method, targetClass, true);
 		// If we found a method in a public interface, return the interface method.
-		if (interfaceMethod != method) {
+		if (interfaceMethod != method && interfaceMethod.getDeclaringClass().getModule().isExported(
+				interfaceMethod.getDeclaringClass().getPackageName(), ClassUtils.class.getModule())) {
 			return interfaceMethod;
 		}
 
-		Class<?> declaringClass = method.getDeclaringClass();
 		// Bypass cache for java.lang.Object unless it is actually an overridable method declared there.
 		if (declaringClass.getSuperclass() == Object.class && !ReflectionUtils.isObjectMethod(method)) {
 			return method;
@@ -1540,7 +1543,9 @@ private static Method findPubliclyAccessibleMethodIfPossible(
 			if (method == null) {
 				break;
 			}
-			if (Modifier.isPublic(method.getDeclaringClass().getModifiers())) {
+			if (Modifier.isPublic(method.getDeclaringClass().getModifiers()) &&
+					method.getDeclaringClass().getModule().isExported(
+							method.getDeclaringClass().getPackageName(), ClassUtils.class.getModule())) {
 				result = method;
 			}
 			current = method.getDeclaringClass().getSuperclass();

spring-core/src/test/java/org/springframework/util/ClassUtilsTests.java

@@ -27,6 +27,7 @@
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Proxy;
+import java.net.URLConnection;
 import java.time.ZoneId;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -687,13 +688,13 @@ void publicMethodInNonPublicInterface() throws Exception {
 		}
 
 		@Test
-		void publicMethodInObjectClass() throws Exception {
+		void publicMethodInPublicClass() throws Exception {
 			Class<?> originalType = String.class;
-			Method originalMethod = originalType.getDeclaredMethod("hashCode");
+			Method originalMethod = originalType.getDeclaredMethod("toString");
 
 			Method publiclyAccessibleMethod = ClassUtils.getPubliclyAccessibleMethodIfPossible(originalMethod, null);
-			assertThat(publiclyAccessibleMethod.getDeclaringClass()).isEqualTo(Object.class);
-			assertThat(publiclyAccessibleMethod.getName()).isEqualTo("hashCode");
+			assertThat(publiclyAccessibleMethod.getDeclaringClass()).isEqualTo(originalType);
+			assertThat(publiclyAccessibleMethod).isSameAs(originalMethod);
 			assertPubliclyAccessible(publiclyAccessibleMethod);
 		}
 
@@ -703,9 +704,20 @@ void publicInterfaceMethodInPublicClass() throws Exception {
 			Method originalMethod = originalType.getDeclaredMethod("size");
 
 			Method publiclyAccessibleMethod = ClassUtils.getPubliclyAccessibleMethodIfPossible(originalMethod, null);
-			// Should find the interface method in List.
-			assertThat(publiclyAccessibleMethod.getDeclaringClass()).isEqualTo(List.class);
-			assertThat(publiclyAccessibleMethod.getName()).isEqualTo("size");
+			// Should not find the interface method in List.
+			assertThat(publiclyAccessibleMethod.getDeclaringClass()).isEqualTo(originalType);
+			assertThat(publiclyAccessibleMethod).isSameAs(originalMethod);
+			assertPubliclyAccessible(publiclyAccessibleMethod);
+		}
+
+		@Test
+		void publicMethodInNonExportedClass() throws Exception {
+			Class<?> originalType = getClass().getClassLoader().loadClass("sun.net.www.protocol.http.HttpURLConnection");
+			Method originalMethod = originalType.getDeclaredMethod("getOutputStream");
+
+			Method publiclyAccessibleMethod = ClassUtils.getPubliclyAccessibleMethodIfPossible(originalMethod, null);
+			assertThat(publiclyAccessibleMethod.getDeclaringClass()).isEqualTo(URLConnection.class);
+			assertThat(publiclyAccessibleMethod.getName()).isSameAs(originalMethod.getName());
 			assertPubliclyAccessible(publiclyAccessibleMethod);
 		}