columns.add(new PropertyColumn<Contact, String>(new Model<String>("Home Phone"), "homePhone"));
columns.add(new PropertyColumn<Contact, String>(new Model<String>("Cell Phone"), "cellPhone"));
DataTable dataTable = new DefaultDataTable<Contact, String>("table", columns,
new SortableContactDataProvider(), 8);
dataTable.addBottomToolbar(new ExportToolbar(dataTable).addDataExporter(new CSVDataExporter()));
add(dataTable);
DataTable tableWithColGroup = new DataTable("tableWithColGroup", columns,
new SortableContactDataProvider(), 8);