Use MethodInvocationInfo class loader in case of JDK platform loader as well

Closes gh-30210

Author: jhoeller

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/MvcUriComponentsBuilder.java

@@ -780,7 +780,9 @@ private static <T> T initProxy(
 
 			else if (controllerType.isInterface()) {
 				ClassLoader classLoader = controllerType.getClassLoader();
-				if (classLoader == null) {  // JDK interface type from bootstrap loader
+				if (classLoader == null || classLoader.getParent() == null) {
+					// JDK interface type from bootstrap loader or platform loader ->
+					// use higher-level loader which can see Spring infrastructure classes
 					classLoader = MethodInvocationInfo.class.getClassLoader();
 				}
 				Class<?>[] ifcs = new Class<?>[] {controllerType, MethodInvocationInfo.class};

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/MvcUriComponentsBuilderTests.java

@@ -21,6 +21,7 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
+import java.sql.Savepoint;
 import java.util.Arrays;
 import java.util.Date;
 import java.util.List;
@@ -384,14 +385,6 @@ public void fromMethodCallWithObjectReturnType() {
 		assertThat(uriComponents.encode().toUri().toString()).isEqualTo("http://localhost/hotels/42/bookings/21");
 	}
 
-	@Test  // SPR-16710
-	public void fromMethodCallWithCharSequenceReturnType() {
-		UriComponents uriComponents = fromMethodCall(
-				on(BookingControllerWithCharSequence.class).getBooking(21L)).buildAndExpand(42);
-
-		assertThat(uriComponents.encode().toUri().toString()).isEqualTo("http://localhost/hotels/42/bookings/21");
-	}
-
 	@Test  // SPR-16710
 	public void fromMethodCallWithStringReturnType() {
 		assertThatIllegalStateException().isThrownBy(() -> {
@@ -409,6 +402,22 @@ public void fromMethodNameWithStringReturnType() {
 		assertThat(uriComponents.encode().toUri().toString()).isEqualTo("http://localhost/hotels/42/bookings/21");
 	}
 
+	@Test  // gh-30210
+	public void fromMethodCallWithCharSequenceReturnType() {
+		UriComponents uriComponents = fromMethodCall(
+				on(BookingControllerWithCharSequence.class).getBooking(21L)).buildAndExpand(42);
+
+		assertThat(uriComponents.encode().toUri().toString()).isEqualTo("http://localhost/hotels/42/bookings/21");
+	}
+
+	@Test  // gh-30210
+	public void fromMethodCallWithJdbc30115ReturnType() {
+		UriComponents uriComponents = fromMethodCall(
+				on(BookingControllerWithJdbcSavepoint.class).getBooking(21L)).buildAndExpand(42);
+
+		assertThat(uriComponents.encode().toUri().toString()).isEqualTo("http://localhost/hotels/42/bookings/21");
+	}
+
 	@Test
 	public void fromMappingNamePlain() {
 		initWebApplicationContext(WebConfig.class);
@@ -716,6 +725,17 @@ public Object getBooking(@PathVariable Long booking) {
 	}
 
 
+	@Controller
+	@RequestMapping("/hotels/{hotel}")
+	static class BookingControllerWithString {
+
+		@GetMapping("/bookings/{booking}")
+		public String getBooking(@PathVariable Long booking) {
+			return "url";
+		}
+	}
+
+
 	@Controller
 	@RequestMapping("/hotels/{hotel}")
 	static class BookingControllerWithCharSequence {
@@ -729,11 +749,11 @@ public CharSequence getBooking(@PathVariable Long booking) {
 
 	@Controller
 	@RequestMapping("/hotels/{hotel}")
-	static class BookingControllerWithString {
+	static class BookingControllerWithJdbcSavepoint {
 
 		@GetMapping("/bookings/{booking}")
-		public String getBooking(@PathVariable Long booking) {
-			return "url";
+		public Savepoint getBooking(@PathVariable Long booking) {
+			return null;
 		}
 	}