FIX: do not hit database if inherited entity has no children (#974)

* FIX: do not hit database if inherited entity has no children

* ADD: Testcase for creating references of inherited beans

src/main/java/io/ebeaninternal/server/core/DefaultServer.java

@@ -612,7 +612,7 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     }
 
     InheritInfo inheritInfo = desc.getInheritInfo();
-    if (inheritInfo == null) {
+    if (inheritInfo == null || inheritInfo.getChildren().isEmpty()) {
       return (T) desc.contextRef(pc, null, false, id);
     }
 

src/main/java/io/ebeaninternal/server/deploy/InheritInfo.java

@@ -164,7 +164,14 @@ public class InheritInfo {
   public BeanProperty[] localProperties() {
     return descriptor.propertiesLocal();
   }
-
+  
+  /**
+   * Return the children.
+   */
+  public ArrayList<InheritInfo> getChildren() {
+    return children;
+  }
+  
   /**
    * Get the bean property additionally looking in the sub types.
    */

src/test/java/org/tests/inheritance/TestInheritanceRefBean.java

@@ -0,0 +1,40 @@
+package org.tests.inheritance;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.avaje.ebeantest.LoggedSqlCollector;
+import org.avaje.test.model.rawsql.inherit.ChildA;
+import org.avaje.test.model.rawsql.inherit.ChildB;
+import org.avaje.test.model.rawsql.inherit.Parent;
+import org.junit.Test;
+
+import io.ebean.BaseTestCase;
+
+public class TestInheritanceRefBean extends BaseTestCase {
+
+    @Test
+    public void test() {
+      Parent a = new ChildA(42, "Bean A");
+      Parent b = new ChildB(43, "Bean B");
+      
+      server().save(a);
+      server().save(b);
+      Long idA = a.getId();
+      Long idB = b.getId();
+      
+      Parent test;
+      
+      LoggedSqlCollector.start();
+      test = server().getReference(ChildA.class, idA);
+      assertTrue(test instanceof ChildA);
+      assertEquals(0, LoggedSqlCollector.stop().size());
+      
+      LoggedSqlCollector.start();
+      test = server().getReference(Parent.class, idB);
+      assertTrue(test instanceof ChildB);
+      assertEquals(1, LoggedSqlCollector.stop().size());
+      
+      
+    }
+}