Building a WML Application with Enhydra

Doing Things the Enhydra Way

Saying that Enhydra promotes a way of doing things would be better than saying it makes you do things a certain way. The Enhydra tools are built to use a 3-tier architecture by default that separates your presentation, business, and data classes. However, the default setup is just there to help you get started: you can build a client-server type application with Enhydra if you wish. I often build all my data, business, and presentation logic all in the presentation layer for prototyping, and then figure out the best way to separate them cleanly before building my final product. I highly recommend that you follow the 3-tier architecture in your final product, especially if you plan to publish to multiple platforms.

Enhydra also suggests that you follow certain standards. The XMLC tool uses the Java port of Tidy (JTidy) as the default parser, and will notify you if you don't close tags properly or use unsupported tags. These are only warnings, though, and they can be ignored if you don't mind the messages. One thing to note is that the parser will automatically create "correct" HTML for output. This can cause some difficulty with complex layouts that rely on invalid HTML for proper placement of page items. In cases where adherence to the standards is required, such as writing WML or XML, Enhydra can force you to follow the proper markup language and prevent a lot of headaches during development.

Now that the high-level introduction to Enhydra is taken care of, let's talk about what you need to know to use it effectively. Enhydra uses the UNIX philosophy of building upon multiple pieces that all do their job well, so the list of things to know is relatively long. A comforting thought to consider is that most of these will at least be familiar to a person developing for the Web and/or WAP anyway:

Ø       Java 1.1

Ø       XML (WML, XHTML)

Ø       HTML

Ø       W3C Document Object Model (DOM) - http://www.w3c.org/

Ø       Java servlets - not essential, as the framework takes care of this part anyway, but knowing how they work is a great help.