The graduate student presenations are scheduled for April 28. They should be around 10 to 15 minutes long. Every graduate student taking this class must do a presentation. For these presentations simply choose a technology (javascript library, web service API, development environment, etc.) that has not been covered in class and tell us about it: what are its pros and cons? how does it compare to other approaches?

I have posted the requirements for the final project as well as a couple of ideas for possible projects, but I am sure you can come up with better ideas yourself.

When you email me your PS3, as well as the final project later on, make sure you specify who worked on the project and which specific parts of the project each person worked on.

Today in class Adam asked: why are there so many programming languages? Just now my wife asked me the same question as I was busy reading my ruby on rails book, which she thought was a new rock band. I think I now have a succint answer.

There are a lot of programming languages for the same set of reasons that explain why there are so many tools, many of which do the same thing, at the Home Depot. If you have a garage full of tools, like I do, then you know what these reasons are.

I know I've mentioned this a lot in class but there is a new example of the web as a platform that surprised me. The game Spore (from the guy that gave us SimCity et al) automatically uploads movies of your spore to youtube. This has been made possible by the new Youtube API, check out their video introduction. We are just at the beginning. Expect to see an explosion of web-enabled software to appear over the next 10 years. In fact, I expect that within a decade all software will use some kind of web back end with few exceptions.

I have posted problem set 3 so you can get an early start on it. This problem set requires you to use your full AJAX skills: Javascript + HTMl + CSS + Java Servlets + JSON libs. You don't need to use a database but you can, if you want. Specifically, you can use grab my netbeans + derby code to get you started on using JDBC to interact with the Java DB (derby) which comes with Netbeans. You could use the database to keep track of the pictures and, if you choose, user nicknames and high scores.

Also, feel free to improve on my game if you think you can make it more engaging.

I have moved the PS 2 due date back to March 17, but note that PS 3 will be due two weeks later on March 31. I will be posting PS 3 next week.

Here are a few tips based on common mistakes I've seen in the past:

• Start by writing small functions. Constantly test these functions in the firebug console to make sure they do what you expect (unit testing!). Then build more complex functions based on these simple functions.
• Use the firebug debugger. Traversing the DOM is scary. It really helps to step over your code to make sure all variables hold the values you expect.
• The DOM can include seemingly random text nodes (nodeType = 3) whose content is only whitespace. These often cause havoc when you are traversing the DOM tree and assuming that all you will find are Element nodes (nodeType = 1). An easy fix is to write your HTML with no whitespace between tags, of course, you do need a space between a tag name and its attribute.
• You can use firebug to see how the HTML in your page looks after your javascript has run. Do this to make sure that the changes you made are what you wanted to make. Not only that but, if you are looking at the "inspect" tab while your javascript code adds some nodes then these new nodes will be highlighted.
• The DOM tab in firebug can be useful, even if cumbersome.
• gotapi.com
• The DOM is a live datastructre that represents what the user is seeing. Whatever you change on the DOM will be immediately shown to the user. All you have to do is change the DOM (thus the HTML page) so that it looks the way you want.
• If you put Nodes in an array and then delete one of them by doing a removeChild then the array will shrink by one, all indices bigger than the one it had will change. Remember that arrays are not really arrays in JavaScript, they are hash tables pretending to be arrays, sometimes not so successfully.

If you are feeling overwhelment by Javascript + DOM, I highly recomment these quick reference cards. You can download one for Javascript, which also includes a bit of the DOM, and another one for CSS. Here is another one

I have just posted the new PS 2. We have not covered enough of javascript for you to be able to get started, but you can get started reading the google chart API.

There is a javascript plugin for netbeans available, and here is the FAQ on how to install a plugin for netbeans. I installed it and it does syntax coloring and building a function tree but not much else, as fas as I can see.

If you are looking for a more leisurely introduction to Java Servlets and don't want to pay, I recomment these books.

Here is the code for the mentalist servlet I demoed in class today. It is a good simple example of how to use the session object.

Problem Set 1 has been posted. We will start covering Java Servlets this Monday. I suggest you install and play with netbeans if you have not done so (you want the "Web & Java EE" version, or the "all")

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