Fix JAX-RS Application class hierarchy handling

extensions/resteasy-classic/resteasy-server-common/deployment/src/main/java/io/quarkus/resteasy/server/common/deployment/ResteasyServerCommonProcessor.java

@@ -953,6 +953,9 @@ private static Set<String> getAllowedClasses(IndexView index) {
         Application application;
         ClassInfo selectedAppClass = null;
         for (ClassInfo applicationClassInfo : applications) {
+            if (Modifier.isAbstract(applicationClassInfo.flags())) {
+                continue;
+            }
             if (selectedAppClass != null) {
                 throw new RuntimeException("More than one Application class: " + applications);
             }

extensions/resteasy-classic/resteasy/deployment/src/test/java/io/quarkus/resteasy/test/root/ApplicationPathHttpRootTest.java

@@ -23,7 +23,7 @@ public class ApplicationPathHttpRootTest {
     @RegisterExtension
     static QuarkusUnitTest runner = new QuarkusUnitTest()
             .setArchiveProducer(() -> ShrinkWrap.create(JavaArchive.class)
-                    .addClasses(HelloResource.class, HelloApp.class)
+                    .addClasses(HelloResource.class, HelloApp.class, BaseApplication.class)
                     .addAsResource(new StringAsset("quarkus.http.root-path=/foo"), "application.properties"));
 
     @Test
@@ -44,7 +44,11 @@ public String hello() {
     }
 
     @ApplicationPath("hello")
-    public static class HelloApp extends Application {
+    public static class HelloApp extends BaseApplication {
+
+    }
+
+    public static abstract class BaseApplication extends Application {
 
     }
 

extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/path/RestApplicationPathTestCase.java

@@ -20,7 +20,7 @@ public class RestApplicationPathTestCase {
             .overrideConfigKey("quarkus.rest.path", "/foo")
             .overrideConfigKey("quarkus.http.root-path", "/app")
             .setArchiveProducer(() -> ShrinkWrap.create(JavaArchive.class)
-                    .addClasses(HelloResource.class, BarApp.class));
+                    .addClasses(HelloResource.class, BarApp.class, BaseApplication.class));
 
     /**
      * Using @ApplicationPath will overlay/replace `quarkus.rest.path`.
@@ -33,7 +33,10 @@ public class RestApplicationPathTestCase {
      * This path will also be relative to the configured HTTP root
      */
     @ApplicationPath("/bar")
-    public static class BarApp extends Application {
+    public static class BarApp extends BaseApplication {
+    }
+
+    public static abstract class BaseApplication extends Application {
     }
 
     @Test

independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/scanning/ResteasyReactiveScanner.java

@@ -59,6 +59,9 @@ public static ApplicationScanningResult scanForApplicationClass(IndexView index,
         ClassInfo selectedAppClass = null;
         boolean blocking = false;
         for (ClassInfo applicationClassInfo : applications) {
+            if (Modifier.isAbstract(applicationClassInfo.flags())) {
+                continue;
+            }
             if (selectedAppClass != null) {
                 throw new RuntimeException("More than one Application class: " + applications);
             }