Another question that has come up in the course of my recent postings is how to bind a combo box selection to a JTable's elements (so that the rows of the table are determined by the selected item of the combo box).

Here are some rough steps to mocking up this behavior. These steps assume that you want db connectivity for the app and that you have a db based on the sql script here: http://weblogs.java.net/blog/pkeegan/archive/2008/05/input_on_a_new.html . Be sure to populate the db tables with actual data.

First we'll create the project, entity classes, and the form:

1. Create a new Java Application project.
2. Use the Entity Class from Database template in the New File wizard to create entity classes for the Clients and Orders db tables. Leave the Include Related Tables checkbox selected. (A class for the Countries table will also be generated, though we will not use it.)
3. In the last page of the wizard, be sure to create a persistence unit.
4. Create a new JFrame.
5. Add a JComboBox and JTable.

Now we'll create a list of Clients and bind the combo box to that list.

1. Right-click the combo box and choose Bind -> elements.
2. Click Import Data to Form and choose the the appropriate db connection and the clients table.

   This step generates the list object.

3. Make sure clientsList is shown as the binding source and click OK.

At this point, you would might expect to be able to right-click the JTable, select Bind | elements, and bind to the selectedItem property of the combo box. (In fact, you can do this in NetBeans 6.5, and you might even want to try it in the upcoming M1 build). However, in NetBeans 6.1, the code generation for the binding between the JTable elements and the combo box's selectedItem doesn't work as you might expect. The generated code assumes that the selected item is a plain Object, not a Clients object with sub-properties that can be represented by columns. So ColumnBindings code is not generated. You can work around this problem with some manual coding:

1. Right-click the JTable and choose Customize Code.
2. *Above* the jScrollPane1.setViewportView(jTable1); line, insert the following code:

   org.jdesktop.beansbinding.ELProperty eLProperty = org.jdesktop.beansbinding.ELProperty.create("${selectedItem.ordersCollection}");
   org.jdesktop.swingbinding.JTableBinding jTableBinding = org.jdesktop.swingbinding.SwingBindings.createJTableBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, jComboBox1, eLProperty, jTable1);
   org.jdesktop.swingbinding.JTableBinding.ColumnBinding columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${product}"));
          columnBinding.setColumnName("Product");
          columnBinding.setColumnClass(String.class);
          columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${amount}"));
          columnBinding.setColumnName("Amount");
          columnBinding.setColumnClass(Integer.class);
          jTableBinding.setSourceUnreadableValue(null);
          bindingGroup.addBinding(jTableBinding);
          jTableBinding.bind();
   

3. Click OK to close the Customize Code dialog box.
4. Select the table and click the Properties button in the Properties window.
5. For the model property, click the ellipsis (...) button to open the property editor.
6. Click Reset to Default. This removes the superfluous table model that is generated when you add the table to the form but which is rendered obsolete by the binding code you have just added.

When you run the application, the JTable should respond to the selection in the combo box, as shown below.

You still need to write a custom renderer for the JTable so that it shows human-relevant text (such as the name of one of the table columns). That task is covered here: http://weblogs.java.net/blog/pkeegan/archive/2007/10/binding_jcombob.html