Specific check for parent of spring-aop ClassLoader

Also applied to getProxyClass now.

Closes gh-30389

spring-aop/src/main/java/org/springframework/aop/framework/JdkDynamicAopProxy.java

@@ -120,18 +120,39 @@ public Object getProxy(@Nullable ClassLoader classLoader) {
 		if (logger.isTraceEnabled()) {
 			logger.trace("Creating JDK dynamic proxy: " + this.advised.getTargetSource());
 		}
-		if (classLoader == null || classLoader.getParent() == null) {
-			// JDK bootstrap loader or platform loader suggested ->
-			// use higher-level loader which can see Spring infrastructure classes
-			classLoader = getClass().getClassLoader();
-		}
-		return Proxy.newProxyInstance(classLoader, this.proxiedInterfaces, this);
+		return Proxy.newProxyInstance(determineClassLoader(classLoader), this.proxiedInterfaces, this);
 	}
 
 	@SuppressWarnings("deprecation")
 	@Override
 	public Class<?> getProxyClass(@Nullable ClassLoader classLoader) {
-		return Proxy.getProxyClass(classLoader, this.proxiedInterfaces);
+		return Proxy.getProxyClass(determineClassLoader(classLoader), this.proxiedInterfaces);
+	}
+
+	/**
+	 * Determine whether the JDK bootstrap or platform loader has been suggested ->
+	 * use higher-level loader which can see Spring infrastructure classes instead.
+	 */
+	private ClassLoader determineClassLoader(@Nullable ClassLoader classLoader) {
+		if (classLoader == null) {
+			// JDK bootstrap loader -> use spring-aop ClassLoader instead.
+			return getClass().getClassLoader();
+		}
+		if (classLoader.getParent() == null) {
+			// Potentially the JDK platform loader on JDK 9+
+			ClassLoader aopClassLoader = getClass().getClassLoader();
+			ClassLoader aopParent = aopClassLoader.getParent();
+			while (aopParent != null) {
+				if (classLoader == aopParent) {
+					// Suggested ClassLoader is ancestor of spring-aop ClassLoader
+					// -> use spring-aop ClassLoader itself instead.
+					return aopClassLoader;
+				}
+				aopParent = aopParent.getParent();
+			}
+		}
+		// Regular case: use suggested ClassLoader as-is.
+		return classLoader;
 	}
 
 	/**

spring-aop/src/test/java/org/springframework/aop/framework/ProxyFactoryTests.java

@@ -389,7 +389,9 @@ public void testCharSequenceProxy() {
 		CharSequence target = "test";
 		ProxyFactory pf = new ProxyFactory(target);
 		ClassLoader cl = target.getClass().getClassLoader();
-		assertThat(((CharSequence) pf.getProxy(cl)).toString()).isEqualTo(target);
+		CharSequence proxy = (CharSequence) pf.getProxy(cl);
+		assertThat(proxy.toString()).isEqualTo(target);
+		assertThat(pf.getProxyClass(cl)).isSameAs(proxy.getClass());
 	}
 
 	@Test
@@ -398,7 +400,9 @@ public void testDateProxy() {
 		ProxyFactory pf = new ProxyFactory(target);
 		pf.setProxyTargetClass(true);
 		ClassLoader cl = target.getClass().getClassLoader();
-		assertThat(((Date) pf.getProxy(cl)).getTime()).isEqualTo(target.getTime());
+		Date proxy = (Date) pf.getProxy(cl);
+		assertThat(proxy.getTime()).isEqualTo(target.getTime());
+		assertThat(pf.getProxyClass(cl)).isSameAs(proxy.getClass());
 	}
 
 	@Test
@@ -415,7 +419,9 @@ public String getSavepointName() throws SQLException {
 		};
 		ProxyFactory pf = new ProxyFactory(target);
 		ClassLoader cl = Savepoint.class.getClassLoader();
-		assertThat(((Savepoint) pf.getProxy(cl)).getSavepointName()).isEqualTo("sp");
+		Savepoint proxy = (Savepoint) pf.getProxy(cl);
+		assertThat(proxy.getSavepointName()).isEqualTo("sp");
+		assertThat(pf.getProxyClass(cl)).isSameAs(proxy.getClass());
 	}