private DocRef getDestinationFolderRef(final ExplorerNode destinationFolder) {
        if (destinationFolder != null) {
            final DocRef destDocRef = destinationFolder.getDocRef();
            if (!ExplorerConstants.isFolder(destDocRef) && !ExplorerConstants.isRootNode(destinationFolder)) {
                throw new IllegalArgumentException(destDocRef + " is not a valid destination folder");
            }
            return destDocRef;
        }

        final ExplorerNode rootNode = explorerNodeService.getRoot();
        return rootNode != null
                ? rootNode.getDocRef()
                : null;
    }
Returns the DocRef of a destination folder

@param destinationFolder If null, looks up the default root node
stroom-explorer/stroom-explorer-impl/src/main/java/stroom/explorer/impl/ExplorerServiceImpl.java