NPE when trying to find rootTable about datanucleus-mongodb HOT 7 CLOSED

String org.datanucleus.store.mongodb.MongoDBUtils.getClassNameForIdentity(Object id, AbstractClassMetaData rootCmd, ExecutionContext ec, ClassLoaderResolver clr)
{
        Map<String, Set<String>> classNamesByDbCollectionName = new HashMap<>();
        StoreManager storeMgr = ec.getStoreManager();
        Set rootClassNames = new HashSet<String>();
        rootClassNames.add(rootCmd.getFullClassName());
        StoreData storeData = storeMgr.getStoreDataForClass(rootCmd.getFullClassName()); //comment: since my root class is abstract there is no entry in the table storeDataMgr.storeDataByClass, so storeData is null
        Table rootTable = null;
        String rootTableName = "";
        if (storeData != null)
        {
            rootTable = storeData.getTable();
            rootTableName = rootTable.getName();
        }
        else
        {
            // how to access the rootTable via name?
            rootTableName = rootCmd.getTable(); //comment: since storeData is null, rootTable is also null
        }
        classNamesByDbCollectionName.put(rootTableName, rootClassNames);
        Collection<String> subclassNames = storeMgr.getSubClassesForClass(rootCmd.getFullClassName(), true, clr);
        if (subclassNames != null && !subclassNames.isEmpty())
        {
            for (String subclassName : subclassNames)
            {
                AbstractClassMetaData cmd =  ec.getMetaDataManager().getMetaDataForClass(subclassName, clr);
                StoreData subStoreData = storeMgr.getStoreDataForClass(cmd.getFullClassName());
                Table subTable = null;
                String subTableName = "";
                if (subStoreData != null)
                {
                    subTable = subStoreData.getTable();
                    subTableName = subTable.getName();
                }
                else
                {
                    // how to access the subTable via name?
                    subTableName = cmd.getTable();
                }
                // Table subTable = storeMgr.getStoreDataForClass(cmd.getFullClassName()).getTable();
                // String subTableName = subTable.getName();
                Set<String> classNames = classNamesByDbCollectionName.get(subTableName);
                if (classNames == null)
                {
                    classNames = new HashSet<String>();
                    classNamesByDbCollectionName.put(subTableName, classNames);
                }
                classNames.add(cmd.getFullClassName());
            }
        }

        ManagedConnection mconn = storeMgr.getConnection(ec);
        try
        {
            DB db = (DB) mconn.getConnection();

            for (Map.Entry<String, Set<String>> dbCollEntry : classNamesByDbCollectionName.entrySet())
            {
                // Check each DBCollection for the id PK field(s)
                String dbCollName = dbCollEntry.getKey();
                if (dbCollName == null) continue; //comment: I added this. For some reason this is null for some classes, so I have to continue to prevent an NPE
                Set<String> classNames = dbCollEntry.getValue();                
                DBCollection dbColl = db.getCollection(dbCollName);
                BasicDBObject query = new BasicDBObject();
                if (rootCmd.getIdentityType() == IdentityType.DATASTORE)
                {
                    Object key = IdentityUtils.getTargetKeyForDatastoreIdentity(id);
                    if (storeMgr.isStrategyDatastoreAttributed(rootCmd, -1))
                    {
                        query.put("_id", new ObjectId((String) key));
                    }
                    else
                    {
                        query.put(rootTable.getDatastoreIdColumn().getName(), key);
                    }
                }
                else if (rootCmd.getIdentityType() == IdentityType.APPLICATION)
                {
                    if (IdentityUtils.isSingleFieldIdentity(id))
                    {
                        Object key = IdentityUtils.getTargetKeyForSingleFieldIdentity(id);
                        int[] pkNums = rootCmd.getPKMemberPositions();
                        AbstractMemberMetaData pkMmd = rootCmd.getMetaDataForManagedMemberAtAbsolutePosition(pkNums[0]);
                        String pkPropName = rootTable.getMemberColumnMappingForMember(pkMmd).getColumn(0).getName(); //comment: since rootTable is null, this leads to an NPE
                        query.put(pkPropName, key);
                    }
                    else
                    {
                        int[] pkNums = rootCmd.getPKMemberPositions();
                        for (int i = 0; i < pkNums.length; i++)
                        {
                            AbstractMemberMetaData pkMmd = rootCmd.getMetaDataForManagedMemberAtAbsolutePosition(pkNums[i]);
                            String pkPropName = rootTable.getMemberColumnMappingForMember(pkMmd).getColumn(0).getName();
                            Object pkVal = IdentityUtils.getValueForMemberInId(id, pkMmd);
                            query.put(pkPropName, pkVal);
                        }
                    }
                }