diff --git a/foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/sessions/UnitOfWorkImpl.java b/foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/sessions/UnitOfWorkImpl.java
index cc78e3eb38a..20dbec54a40 100644
--- a/foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/sessions/UnitOfWorkImpl.java
+++ b/foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/sessions/UnitOfWorkImpl.java
@@ -3021,7 +3021,7 @@ public Object internalRegisterObject(Object object, ClassDescriptor descriptor,
             return null;
         }
         if (descriptor.isDescriptorTypeAggregate()) {
-            throw ValidationException.cannotRegisterAggregateObjectInUnitOfWork(object.getClass());
+           return null;
         }
         Object registeredObject = checkIfAlreadyRegistered(object, descriptor);
         if (registeredObject == null) {
diff --git a/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/ManagedTypeImpl.java b/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/ManagedTypeImpl.java
index 6cac0be80ba..30a128043ce 100644
--- a/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/ManagedTypeImpl.java
+++ b/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/ManagedTypeImpl.java
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2011, 2021 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020 Payara Services Ltd.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0 which is available at
@@ -87,6 +88,7 @@
 import org.eclipse.persistence.internal.security.PrivilegedAccessHelper;
 import org.eclipse.persistence.internal.security.PrivilegedGetDeclaredField;
 import org.eclipse.persistence.internal.security.PrivilegedGetDeclaredMethod;
+import org.eclipse.persistence.internal.sessions.AbstractSession;
 import org.eclipse.persistence.logging.AbstractSessionLog;
 import org.eclipse.persistence.logging.SessionLog;
 import org.eclipse.persistence.mappings.CollectionMapping;
@@ -1329,6 +1331,18 @@ protected void initialize() { // Future: Check all is*Policy() calls
             this.members.put(mapping.getAttributeName(), member);
         }
     }
+    
+    public void preinitaliseMappings(AbstractSession session) {
+        for (DatabaseMapping mapping : getDescriptor().getMappings()) {
+            try {
+                mapping.preInitialize(session);
+            } catch (NullPointerException npe) {
+                // A NPE gets thrown if the expected method is not present for the mapping
+                AbstractSessionLog.getLog().log(SessionLog.FINE, "Caught NPE when preinitializing database mapping",
+                        npe.getMessage());
+            }
+        }
+    }
 
     /**
      * INTERNAL:
diff --git a/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/MetamodelImpl.java b/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/MetamodelImpl.java
index fbc96566568..c0fb40b6741 100644
--- a/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/MetamodelImpl.java
+++ b/jpa/org.eclipse.persistence.jpa/src/main/java/org/eclipse/persistence/internal/jpa/metamodel/MetamodelImpl.java
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2011, 2021 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020 Payara Services Ltd.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0 which is available at
@@ -464,8 +465,13 @@ public void initialize(ClassLoader classLoader) {
             }
         }
 
-        //1 - process all non-mappedSuperclass types first so we pick up attribute types
-        //2 - process mappedSuperclass types and lookup collection attribute types on inheriting entity types when field is not set
+        //1 - preinitalise all mappings so attribute types are set
+        //2 - process all non-mappedSuperclass types first so we pick up attribute types
+        //3 - process mappedSuperclass types and lookup collection attribute types on inheriting entity types when field is not set
+        
+        for(ManagedTypeImpl<?> managedType : new ArrayList<ManagedTypeImpl<?>>(managedTypes.values())) {
+            managedType.preinitaliseMappings(session);
+        }
 
         /**
          * Delayed-Initialization (process all mappings) of all Managed types
@@ -477,7 +483,7 @@ public void initialize(ClassLoader classLoader) {
             managedType.initialize();
         }
 
-        // 3 - process all the Id attributes on each IdentifiableType
+        // 4 - process all the Id attributes on each IdentifiableType
         for(ManagedTypeImpl<?> potentialIdentifiableType : managedTypes.values()) {
             if(potentialIdentifiableType.isIdentifiableType()) {
                 ((IdentifiableTypeImpl<?>)potentialIdentifiableType).initializeIdAttributes();