How should I rewrite this?

Hello, I have an abstract base class DataModelNode which has a number of
concrete subclasses. Each node can have a set of actions associated with
it. Action is an abstract base class with a number of concrete
subclasses. A given Action is created by an ActionFactory. I need be
able to register which ActionFactories work with a given node
dynamically so I wrote the following class:

package action;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import factory.action.ActionFactory;

import node.DataModelNode;

public class ActionRegistry {

    public static void register(DataModelNode node, ActionFactory action) {
       Set<ActionFactory> actions = null;

       if (actionDecorations.containsKey(node)) {
          actions = actionDecorations.get(node);
       }
       else {
          actions = new HashSet<ActionFactory>();
       }

       actions.add(action);

       actionDecorations.put(node, actions);
    }

    public static Set<ActionFactory> getActionFactories(DataModelNode
node) {
       Set<ActionFactory> actionFactories = actionDecorations.get(node);

       return actionFactories;
    }

    private static final Map<DataModelNode, Set<ActionFactory>>
actionDecorations = new HashMap<DataModelNode, Set<ActionFactory>>();
}

But when I was ready to register a certain ActionFactory with a certain
subclass of DataModelNode (i.e., when I was going to call register()), I
realised my mistake. This code requires an instance of a DataModelNode,
that won't work. I don't have any objects of the nodes when I need to
register. How should I rewrite this registry-class so I can associate
actionfactories with subclasses of DataModelNode? I can post more code
(a small, self-contained test case) if you weren't able to parse the
grammar of my question. Thanks!

- Fencer