Google Web Toolkit Data Grid Example

At work I have a java J2EE application that displays a large table. The report is about 15 MB when rendered. I've been experimenting with GWT and I think it would be a good tool to rewrite this report with.

The main problem with the page is when someone updates a value it has to post back to the server then re-render everything. Using GWT it seems like it would be trivial to reload a single row at a time. Along those lines here is a simple DataGrid example that lets me add/remove rows.

See GWT Simple Example for more information on setting up your environment.

   /*
* mcintoshEntryPoint.java
*
* Created on June 29, 2008, 1:46 PM
*
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
*/
package com.client;

import com.google.gwt.core.client.EntryPoint;
import com.client.time.*;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.ClickListener;
import com.google.gwt.user.client.ui.FlexTable;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.SourcesTableEvents;
import com.google.gwt.user.client.ui.TableListener;
import com.google.gwt.user.client.ui.Widget;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

/**
*
* @author avalanche
*/
public class mcintoshEntryPoint implements EntryPoint {

   final Button addButton = new Button("Add Row");
   final Button deleteButton = new Button("Delete Row");
   final FlexTable table = new FlexTable();   
   final Set selectedTableRows = new HashSet();           

   public mcintoshEntryPoint() {
       addButton.addClickListener(new ClickListener() {

           public void onClick(Widget arg0) {
               table.insertRow(table.getRowCount());
               table.addCell(table.getRowCount() - 1);
               table.addCell(table.getRowCount() - 1);
               table.setText(table.getRowCount() - 1, 1, "foo" + table.getRowCount());               
           }
       });
       deleteButton.addClickListener(new ClickListener() {

           public void onClick(Widget arg0) {
               Object[] array = selectedTableRows.toArray();
               Arrays.sort(array);
               for(int i=array.length-1;i>-1;i-- ) {
                   int row = ((Integer)array[i]).intValue();
                   table.removeRow(row);
                   selectedTableRows.remove(new Integer(row));
               }
           }
       });
       table.addTableListener(new TableListener() {

           public void onCellClicked(SourcesTableEvents arg0, int rrow, int col) {
               Integer row = new Integer(rrow);               
               if (selectedTableRows.contains(row)) {
                   selectedTableRows.remove(row);
                   table.setText(rrow, 0, "x");
               } else {
                   selectedTableRows.add(row);
                   table.setText(rrow, 0, "y");
               }
           }
       });


   }

   /**
    * The entry point method, called automatically by loading a module
    * that declares an implementing class as an entry-point
    */
   public void onModuleLoad() {
       RootPanel.get().add(table);
       RootPanel.get().add(addButton);
       RootPanel.get().add(deleteButton);
   }
}