Step by Step: A Mortgage Calculator using GWT

The following couple of posts are a first for my blog. I have blogged about client projects before, but never have I been paid to do so. But, I currently have a client who enjoys my blog. He also is a big fan of the Google Web Toolkit, and is interested in exploring the usefulness of this toolkit to his website, Colorado HomeFinder (Updated 6/10 with the name of the client, per his request). (Disclaimer: everything I say on this blog is my fault and mine alone.)

So, in the interest of exploration, I’m going to be building a simple mortgage calculator. We’ll be using GWT 1.0.21, developing on Windows XPSP2 and integrating with a existing backend built using Expresso 5.3, a heavyweight open source framework. (I’ve used Expresso before, and written about it, and while the framework is not without its warts, it can be very useful.) I will also be using Eclipse 3.1 to build the code, and be deploying to Linux. FireFox 1.5.0.4 and IE 6.0 (both on Windows XPSP2) will be used to test the application.

I’ll be documenting my missteps and lessons learned as I go. In addition, the client has kindly offered to let me distribute the source on my website, so I’ll be providing a download each step of the way.

Update, Aug 9: Here’s a list of what I’ve written:


Google does spreadsheets

Check out spreadsheets.google.com. Limited time look at what javascript can do for a spreadsheet. I took a quick look and it seems to fit large chunks of what I use Excel or calc, the OpenOffice spreadsheet program, for. Just a quick tour of what I such spreadsheet programs for, and what Google spreadsheet supports:

  • cut and paste, of text and formulas
  • control arrow movement and selection
  • formatting of cells
  • merging of cells and alignment of text in cells
  • undo/redo that goes at least 20 deep
  • sum/count
  • can freeze rows
  • share and save the spreadsheet
  • export to csv and xls

On the other hand, no:

  • dragging of cells to increment them (first cell is 45, next is 46, 47…).
  • using the arrows to select what goes into a formula–you can type in the range or use the mouse

Pretty decent for a web based application. And it does have one killer feature–updates are immediatly propagated (I have never tried to do this with a modern version of Excel, so don’t know if that’s standard behaviour). Snappy enough to use, at least on my relatively modern computer. I looked at the js source and it’s 55k of crazy javascript (Update, 6/9: This link is broken.). Wowsa.

I’ve never used wikicalc but it looks more full featured that Google spreadsheets. On the other hand, Google spreadsheets has a working beta version…

This and the acquisition of writely make me wonder if some folks are correct when they doubt that Google will release a software productivity suite. (More here.) Other interesting comments from Paul Kedrosky.

I know more than one person that absolutely depend on gmail for business functionality, which spooks me. And in some ways, I agree with Paul, it appears that Google “…takes a nuclear winter approach wherein it ruins markets by freezing them and then cutting revenues to zero.”

Personally, if I don’t pay for something, I’m always leery of it being taken away. Of course, if I pay, the service can also go away, but at least I have some more leverage with the company–after all, if they take the service away, they lose money.



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