Problem rendering a dynamically populated tree in a postback

Question

I'll try and keep this as simple as possible...
On page1 I have a table with a button column. When the user presses one of the buttons, the ID for that row is saved in a variable in the session bean, then navigates to page2.
In the init() function of page2 I generate a new tree object using parent/child data retrieved from a database using the ID saved in the session bean. Then I use setTree1(newTree); to apply the data to the component on the page.
The first time a user presses a button on page1, page2 is displayed with the correct data in the tree. If the user navigates back to page1 and presses a different button, page2 is displayed with the tree data from the initial button that was pressed.
I have a number of static text components on page2. The values are updated in the same function that the tree is generated, and all of these get updated correctly in the postback.
Still with me?!
I understand that in the first stage of the lifecycle if the page request is an initial request the the JSF implementation creates an empty view and advances to the render response phase. - eg the first time a button is pressed page2 is shown with the correct tree.
If the page request is a postback a view for this page already exists and the JSF implementation restores the saved view. - eg the second time a button is pressed page2 is shown with the tree data from the first button press.
So my question to you JSF gurus...
Is there some way to make sure that getTree1() is called somewhere in the postback to update the values in the tree, and render the changes on the page.
...or can I make every request to page2 an initial request so that the view isn't saved?
I hope I've been clear on what I'm trying to do here. I've been banging my head against my desk for afew days tryin to figure this out! Thanks in advance for any help
Olly

Answer 1

I set up a test where I use the Travel db and pass a person id from page 1 to page 2. I build a tree of that person's trips in Page 2. Every time I go to Page 2, I get the tree of trips for that person.
On page 2 I have a tree from which I have deleted all nodes. Its ID is displayTree.
Here are excerpts from my prerender code.
           // If nbrChildren is not 0 then we have our tree already
            int nbrChildren = displayTree.getChildCount();
            if (nbrChildren == 0) {
                // List of outer (person) nodes
                List outerChildren = displayTree.getChildren();
                // Erase previous contents
                outerChildren.clear();
                // List of inner (trip) nodes
                List innerChildren = null;
                // Execute the SQL query
< in my loop where I iterate through the query>
                            TreeNode personNode = new TreeNode();
                            personNode.setId("person" + newPersonId.toString());
                            personNode.setText(
                                    (String)tripDataProvider.getValue(
                                    "PERSON.NAME"));
                            // If the request bean passed a person id,
                            // expand that person's node
                            personNode.setExpanded(newPersonId.equals(thisPersonId));
                            outerChildren.add(personNode);
                            innerChildren = personNode.getChildren();
                        // Create a new trip node
                        TreeNode tripNode = new TreeNode();
                        tripNode.setId("trip" +
                                tripDataProvider.getValue("TRIP.TRIPID").toString());
                        tripNode.setText(
                                tripDataProvider.getValue("TRIP.DEPDATE").toString());
                        // Set "action" property to use for navigation
                        tripNode.setAction(
                                getApplication().createMethodBinding
                                ("#{Page1.tripNode_action}", null));
                        innerChildren.add(tripNode);