Dynamic JTree Components

[Craig Snowbarger]

Hello,
Can somebody explain to me, or point me towards an example of a JTree that will dynamically change individual nodes based on criteria from a different component, such as a Resultset? For example, if you wanted each individual node icon to be set according to it's status in the database - if it's "available" it would have a green icon, if it's "not-available" it would have a red icon.
I know that the TreeCellRenderer is used to do this, but as far as I can tell, it only allows one to change parts of the tree according to criteria/parameters specific to the JTree itself like, "selected", "leaf", "parent", "expanded". Is it possible to change parts of the JTree with parameters from different components?
Regards,
Craig Snowbarger

[Anonymous]

When you construct the nodes of your JTree you are passing a UserObject to the constructor for DefaultMutableTreeNode(). You are most likely using a String for this constructor, but that is not your only option. You can pass a custom object, too.
For example, I have a recipe database. I created a recipe object which stores all of the important information of a row in the recipe table. I implemented the toString() method so the Recipe object knows how to display its self as a string. I populated my Recipe object with values from a row in the Recipe table in a database. Then I used my Recipe object as a UserObject to create a node. In this way, each node represents all of the important information found in a record in my recipe database.
Is this what you meant?

[Craig Snowbarger]

That may be what I meant, I'm not for sure. Here is a snippet of my JTree Constructor. My JTree is created dynamically from information in a database. You'll have to forgive me for the sloppy code. I hope you can understand it. I guess my Userobject used to create my nodes are strings from my queries.

    private void makeTree(Toolkit toolkit) {
        /* Create root treenode and add "Make" nodes to it. */
        DefaultMutableTreeNode root =
        new DefaultMutableTreeNode("Test Equipment");
        //query for "Makes" from the Equipment table
        try {
            Statement stmt = dbconn.createStatement();
            String query =  "SELECT DISTINCT Make " +
            "FROM Equipment " +
            "ORDER BY Make";
            ResultSet rs = stmt.executeQuery( query );
            while(rs.next()){
                String s2 = rs.getString("Make");
                DefaultMutableTreeNode makechild =
                new DefaultMutableTreeNode(s2);
                root.add(makechild);
            }//end of "Make" while
            stmt.close();
        } catch ( SQLException sqlex ) {
            sqlex.printStackTrace();
        }//end of catch
        
/*Count the number of nodes in rootNode and
 *place count into condition of for statement.
 *Then, iterate through root children and
 *add make nodes to mode nodes*/
        int countA = root.getChildCount();
        for (int indexA = 0; indexA < countA; indexA++){
            String make = root.getChildAt(indexA).toString();
            try {
                Statement stmt = dbconn.createStatement();
                String query = "SELECT DISTINCT Model " +
                "FROM Equipment " +
                "WHERE Make = '" + make + "' " +
                "ORDER BY Model";
                ResultSet rs = stmt.executeQuery( query );
                while(rs.next()){
                    String s3 = rs.getString("Model");
                    DefaultMutableTreeNode modelchild =
                    new DefaultMutableTreeNode(s3);
                    /*You must cast the rootchild b/c the
                     *compiler sees it as a normal TreeNode
                     *rather than a DefaultMutableTreeNode.*/
                    DefaultMutableTreeNode rootchild =
                    (DefaultMutableTreeNode)root.getChildAt(indexA);
                    //retrieve makechild node from root
                    rootchild.add(modelchild);
                }//end of while
            }//end of try
            catch ( SQLException sqlex ) {
                sqlex.printStackTrace();
            }//end of catch
        }//end of "Model" for loop
        
/*Iterate through Tree and add TestSetID's to
 *model nodes under make nodes*/
        int countB = root.getChildCount();
        for (int indexB = 0; indexB < countB; indexB++){
            DefaultMutableTreeNode rootchild2 =
            (DefaultMutableTreeNode)root.getChildAt(indexB);
            int countC = rootchild2.getChildCount();//"Make" child count
            for (int indexC = 0; indexC < countC; indexC++){
                String make = rootchild2.getChildAt(indexC).toString();
                try {
                    Statement stmt = dbconn.createStatement();
                    String query = "SELECT TestSetID " +
                    "FROM Equipment " +
                    "WHERE Model = '" + make + "' " +
                    "ORDER BY TestSetID";
                    ResultSet rs = stmt.executeQuery( query );
                    while(rs.next()){
                        String s4 = rs.getString("TestSetID");
                        DefaultMutableTreeNode id =
                        new DefaultMutableTreeNode(s4);
                        DefaultMutableTreeNode rootchild3 =
                        (DefaultMutableTreeNode)rootchild2.getChildAt(indexC);
                        rootchild3.add(id);
                    }//end of while
                }//end of try
                catch ( SQLException sqlex ) {
                    sqlex.printStackTrace();
                }//end of catch
            }//end of "Make" for loop
        }//end of "TestSetID" for loop
        
        tree = new JTree(root);
        tree.setCellRenderer(new MyCellRenderer());
        //tree.setExpandedState(path, state)
        tree.putClientProperty("JTree.lineStyle", "Angled");
        tree.getSelectionModel().setSelectionMode
        (TreeSelectionModel.SINGLE_TREE_SELECTION);
        //Listen for when the selection changes.
        tree.addTreeSelectionListener(new TreeSelectionListener() {
            public void valueChanged(TreeSelectionEvent e) {
                treeValueChanged();
            }
        });
    }//end of makeTree()

[Anonymous]

Yup, I feel your pain. I started out by doing mine almost exactly like that. I ended up making some changes. Here is a suggestion for a change you could make that would make your tree more OO.

    private class Equipment
    {
    // this class will have a member for each column in the equipment table
    // it will also store a reference to the icon for this node
    // it MUST implement toString() or it won't be able to display
    // its self in the tree node
    }
    Equipment e;
    ResultSet rs = stmt.executeQuery( query );
        while(rs.next())
            {
                e = new Equipment();
                e.setModel(rs.getString("Model"));
                e.setTestType(rs.getString("TestType"));
                e.setNodeIcon(rs.getString("IconPath"));
                DefaultMutableTreeNode modelchild = new DefaultMutableTreeNode(e);
                DefaultMutableTreeNode rootchild = (DefaultMutableTreeNode)root.getChildAt(indexA);
                rootchild.add(modelchild);
            }

Now when you get ready to do something with your node, it is actually an object of type Equipment. It knows all kinds of stuff about its self, including which icon it is supposed to use to display its self.
Please excuse the sloppieness of my code.

[Martin Schneider]

Hi,
I found this topic and I decided to continue this because I have basically same kind of problem.
So how I can create JTree using Value isParent that is taken from db? I mean there is always root and after that comes those nodes who has value 0 as their isParent value. After that starts some kind of recursive loop where all the children are created. Im totally lost so please help?