Register server exception mapper method of the Rest-Interface implementation class

extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/customexceptions/ImplClassExceptionMapperTest.java

@@ -0,0 +1,100 @@
+package io.quarkus.resteasy.reactive.server.test.customexceptions;
+
+import static io.quarkus.resteasy.reactive.server.test.ExceptionUtil.removeStackTrace;
+
+import java.util.function.Supplier;
+
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.Produces;
+import jakarta.ws.rs.core.Response;
+
+import org.jboss.resteasy.reactive.server.ServerExceptionMapper;
+import org.jboss.shrinkwrap.api.ShrinkWrap;
+import org.jboss.shrinkwrap.api.spec.JavaArchive;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkus.resteasy.reactive.server.test.ExceptionUtil;
+import io.quarkus.test.QuarkusUnitTest;
+import io.restassured.RestAssured;
+
+public class ImplClassExceptionMapperTest {
+
+    @RegisterExtension
+    static QuarkusUnitTest test = new QuarkusUnitTest()
+            .setArchiveProducer(new Supplier<>() {
+                @Override
+                public JavaArchive get() {
+                    return ShrinkWrap.create(JavaArchive.class)
+                            .addClasses(CustomResourceImpl.class,
+                                    CustomResource.class,
+                                    GlobalCustomResourceImpl.class,
+                                    GlobalCustomResource.class,
+                                    DefaultCustomResource.class,
+                                    ExceptionUtil.class);
+                }
+            });
+
+    @Test
+    public void test() {
+        RestAssured.get("/custom/error")
+                .then().statusCode(416);
+        RestAssured.get("/stock/error")
+                .then().statusCode(500);
+        RestAssured.get("/default/error")
+                .then().statusCode(417);
+    }
+
+    @Path("default")
+    public static class DefaultCustomResource {
+
+        @ServerExceptionMapper
+        public Response handleThrowable(RuntimeException t) {
+            return Response.status(417).build();
+        }
+
+        @GET
+        @Path("error")
+        @Produces("text/plain")
+        public String throwsException() {
+            throw removeStackTrace(new RuntimeException());
+        }
+    }
+
+    public static class CustomResourceImpl implements CustomResource {
+
+        @ServerExceptionMapper
+        public Response handleThrowable(RuntimeException t) {
+            return Response.status(416).build();
+        }
+
+        public String throwsException() {
+            throw removeStackTrace(new RuntimeException());
+        }
+    }
+
+    @Path("custom")
+    public interface CustomResource {
+        @GET
+        @Path("error")
+        @Produces("text/plain")
+        String throwsException();
+    }
+
+    public static class GlobalCustomResourceImpl implements GlobalCustomResource {
+
+        public String throwsException() {
+            throw removeStackTrace(new RuntimeException());
+        }
+    }
+
+    @Path("stock")
+    public interface GlobalCustomResource {
+
+        @GET
+        @Path("error")
+        @Produces("text/plain")
+        String throwsException();
+    }
+}

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

@@ -284,6 +284,18 @@ public static ResourceScanningResult scanResources(
                         if (!scannedResources.containsKey(clazz.name())) {
                             scannedResources.put(clazz.name(), clazz);
                             scannedResourcePaths.put(clazz.name(), i.getValue());
+
+                            // check for server exception mapper method in implementation class of the interface.
+                            List<AnnotationInstance> exceptionMapperAnnotationInstances = clazz.annotationsMap()
+                                    .get(ResteasyReactiveDotNames.SERVER_EXCEPTION_MAPPER);
+                            if (exceptionMapperAnnotationInstances != null) {
+                                for (AnnotationInstance instance : exceptionMapperAnnotationInstances) {
+                                    if (instance.target().kind() != AnnotationTarget.Kind.METHOD) {
+                                        continue;
+                                    }
+                                    methodExceptionMappers.add(instance.target().asMethod());
+                                }
+                            }
                         }
                     }
                 }