Create proxies for abstract entity classes too in Hibernate ORM

extensions/hibernate-orm/deployment/src/main/java/io/quarkus/hibernate/orm/deployment/ProxyBuildingHelper.java

@@ -44,7 +44,6 @@ private ByteBuddyProxyHelper getByteBuddyProxyHelper() {
     public boolean isProxiable(ClassInfo classInfo) {
         return classInfo != null
                 && !classInfo.isInterface()
-                && !classInfo.isAbstract()
                 && !classInfo.isFinal()
                 && classInfo.hasNoArgsConstructor();
     }

extensions/hibernate-orm/runtime/src/main/java/io/quarkus/hibernate/orm/runtime/customized/QuarkusProxyFactory.java

@@ -69,9 +69,6 @@ public void postInstantiate(String entityName, Class<?> persistentClass, Set<Cla
             else if (Modifier.isFinal(persistentClass.getModifiers())) {
                 reason = "this class is final. Your application might perform better if this class was non-final.";
             }
-            if (Modifier.isAbstract(persistentClass.getModifiers())) {
-                reason = "this class is abstract. Your application might perform better if this class was non-abstract.";
-            }
             if (reason != null) {
                 // This is caught and logged as a warning by Hibernate ORM.
                 throw new HibernateException(String.format(Locale.ROOT,

integration-tests/jpa/src/main/java/io/quarkus/it/jpa/proxy/ProxyTestEndpoint.java

@@ -12,6 +12,8 @@
 import jakarta.ws.rs.Produces;
 import jakarta.ws.rs.core.MediaType;
 
+import org.hibernate.proxy.HibernateProxy;
+
 import io.quarkus.narayana.jta.QuarkusTransaction;
 import io.quarkus.narayana.jta.runtime.TransactionConfiguration;
 import io.quarkus.runtime.StartupEvent;
@@ -78,6 +80,18 @@ public String testBasic() {
         return "OK";
     }
 
+    @GET
+    @Path("abstract")
+    @Transactional
+    public String testAbstract() {
+        var result = entityManager.getReference(AbstractEntity.class, "1");
+        expectTrue(result != null);
+        expectTrue(result instanceof HibernateProxy);
+        // Make sure we don't get fooled by some kind of "fallback" eager loading
+        expectFalse(result instanceof ConcreteEntity);
+        return "OK";
+    }
+
     /**
      * tests for the @Proxy annotation in an inheritance hierarchy
      *

integration-tests/jpa/src/test/java/io/quarkus/it/jpa/proxy/ProxyTest.java

@@ -1,13 +1,26 @@
 package io.quarkus.it.jpa.proxy;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.hamcrest.Matchers.is;
 
 import org.junit.jupiter.api.Test;
 
+import io.quarkus.test.LogCollectingTestResource;
+import io.quarkus.test.common.QuarkusTestResource;
+import io.quarkus.test.common.ResourceArg;
+import io.quarkus.test.junit.DisabledOnIntegrationTest;
 import io.quarkus.test.junit.QuarkusTest;
 import io.restassured.RestAssured;
 
 @QuarkusTest
+@QuarkusTestResource(value = LogCollectingTestResource.class, restrictToAnnotatedClass = true, initArgs = {
+        @ResourceArg(name = LogCollectingTestResource.LEVEL, value = "WARNING"),
+        @ResourceArg(name = LogCollectingTestResource.INCLUDE, value = "org\\.hibernate\\..*"),
+        // Ignore logs about schema management:
+        // they are unfortunate (https://github.com/quarkusio/quarkus/issues/16204)
+        // but for now we have to live with them.
+        @ResourceArg(name = LogCollectingTestResource.EXCLUDE, value = "org\\.hibernate\\.tool\\.schema.*")
+})
 public class ProxyTest {
 
     @Test
@@ -25,4 +38,26 @@ public void testEnhancedProxies() {
         RestAssured.when().get("/jpa-test/proxy/enhanced").then().body(is("OK"));
     }
 
+    @Test
+    public void testAbstractClassProxies() {
+        RestAssured.when().get("/jpa-test/proxy/abstract").then().body(is("OK"));
+    }
+
+    @Test
+    // When running as integration test, we cannot easily spy on logs.
+    @DisabledOnIntegrationTest
+    public void testProxyWarningsOnStartup() {
+        assertThat(LogCollectingTestResource.current().getRecords())
+                // There shouldn't be any warning or error
+                .as("Startup logs (warning or higher)")
+                .extracting(LogCollectingTestResource::format)
+                .satisfiesExactlyInAnyOrder(
+                        // Final classes cannot be proxied
+                        m -> assertThat(m).contains(
+                                "Could not create proxy factory", CompanyCustomer.class.getName(),
+                                "this class is final", "Your application might perform better if this class was non-final.")
+                // Importantly, we don't expect any other warning about proxies!
+                );
+    }
+
 }

test-framework/junit5-internal/src/main/java/io/quarkus/test/LogCollectingTestResource.java

@@ -25,7 +25,7 @@ public class LogCollectingTestResource implements QuarkusTestResourceLifecycleMa
     public static final String EXCLUDE = "exclude";
     public static final String INCLUDE = "include";
 
-    private static final Formatter LOG_FORMATTER = new PatternFormatter("%s");
+    private static final Formatter LOG_FORMATTER = new PatternFormatter("%m");
 
     public static String format(LogRecord record) {
         return LOG_FORMATTER.format(record);