LastPostInfo is null on forum list

[Migrated From Jforum.net]

See here for the full story, but basically I'm trying to replace the username with a Firstname/Lastname, which I just stuck in an extra field for now rather than re-do the schema. Anyhow, to make the info show up on the forums list, I had to extend ForumAction and add some functionality to retrieve the user ID from the LastPostInfo of each Forum.

The problem is when I first start up JForum, this information always seems to be null. Each request I send seems to fill in 1 forum's LPI, so say I have 5 forums. When I first load it up, all the information is missing. When I refresh, the first forum has its information, and so on, and the forum looks as it should after 5 refreshes. So I have a workaround for now, clearly, but I cannot determine why this information is null at first, and what causes it to be loaded.

For reference, here is my code overriding net.jforum.view.forum.ForumAction#list:

    /**
     * Override base list action to add user objects for all
     * repliers so we can replace username on the view with the
     * user signature, in this case being overridden to contain the
     * poster's full name.
     */
    public void list() {
        super.list();

        //We don't have access to super's local variable
        //for cateogires, so we are going to get them
        //out again even though this is a little bit
        //repetitive.  
        List<Category> categories;
        categories = (List<Category>) ForumCommon.getAllCategoriesAndForums(true);
       
        if (categories == null) return;

        HashMap<Integer, User> lastForumPosters = new HashMap<Integer, User>();
        UserDAO userDAO = DataAccessDriver.getInstance().newUserDAO();

        //Get all the users we need for the view
        for (Category c : categories)
        {
            //Implicit cast to a typed collection
            Collection<Forum> allForums = c.getForums();

            for (Forum f: allForums)
            {
                LastPostInfo lpi = f.getLastPostInfo();
                if (lpi == null) continue;
                int lastPosterId = lpi.getUserId();
                User u = userDAO.selectById(lastPosterId);
                if (u != null)
                {
                    lastForumPosters.put(lastPosterId, u);
                }
            }
        }

        this.context.put("users", lastForumPosters);

    }

Any ideas?
[originally posted on jforum.net by msernatinger]