Building a WML Application with Enhydra

Installing Enhydra

We'll take a high-level look at installing Enhydra first. To install Enhydra for development, you will need the following tools:

 

Ø       Java Developer Kit for version 1.1 of the language

Ø       GNU make environment:

Ø       Requires basic UNIX tools such as sed and awk (free GNU tools available)

Ø       Can use CYGWIN under Win32 environments

Ø       Any other platform with support for GNU make

Ø       Java and markup language editor(s) of your choice:

Ø       XEmacs supports this environment nicely

Ø       Kelp project helps integrate with popular IDEs, such as JBuilder Foundation (Standard, Professional, or Enterprise) and Oracle JDeveloper

 

Enhydra includes a built in web server that is useful for debugging code during the development cycle, but you need to use an external web server for deployment. The web servers that Enhydra is known to work with include:

 

Ø       Apache, through Apache Module Support or the JServ environment

Ø       Netscape server/iPlanet support through NSAPI

Ø       Microsoft IIS support through ISAPI

Ø       Any web server with a servlet runner

Ø       Any web server with CGI support (with obvious performance trade-offs)

 

Another piece worthy of mention is Enhydra Director, enabled by the Module Support listed above. This product enables enterprise level features such as load balancing between multiple instances, and failover for downed machines. Enhydra Director's goal is to let both Enhydra and the complementary web server concentrate on their primary functions. It accomplishes this by using web server specific APIs to listen for files that Enhydra knows how to manipulate. If the web server is trying to serve a .po file, Enhydra will take the request, run the servlet, then send the resulting file to the server. If the web server gets a request for a GIF image, Enhydra quietly ignores this and lets the web server take care of fulfilling that request.

 

Database support is an interesting topic. Enhydra contains a relational-to-object mapping tool called Data Object Design Studio (DODS), further information about which can be found at http://www.enhydra.org/software/documentation/enhydra/DODS.html

DODS is a useful tool that supports many databases, including:

 

Ø       Informix

Ø       Microsoft SQL

Ø       Oracle

Ø       PostgreSQL

Ø       Sybase

Ø       Most databases with standard JDBC support

 

Of course, you can access your database using any tool you'd like. You can use a commercial object-to-relational mapping tool, or talk to JDBC directly and process the result sets yourself. If you choose to talk to JDBC directly, you can use any database with JDBC drivers available on your development and deployment platforms. You can also achieve the same thing with ODBC databases using the standard odbc:jdbc bridge.

 

Now that you know what you need and what you're going to get, you need to know where to get it. Go to http://www.enhydra.org for the latest version and information about the product. You have one more decision though: do you get a source release or a binary distribution? There are a few guidelines to use when making this decision:

Source Code

Ø       You need access to immature features

Ø       You will be adding new features to Enhydra

Ø       You just like to have the latest version of the software, and it is useful to be able to correct bugs that you find in the engine and not have to wait for a service pack/update release.

Binary Release

Ø       Enhydra currently supports everything you want to accomplish

Ø       You don't want to compile the source code

Ø       You feel more confident about officially sanctioned releases

 

Either way, I recommend at least downloading the source, just in case you decide to look through it.

 

This is definitely not a thorough explanation of installing Enhydra, so the following URLs will provide further help (as well as being interesting!) if you need it:

http://www.enhydra.org/software/documentation/enhydra/index.html
http://www.enhydra.org/home/faq/cache/1.html

If you'll be using the product, you should also sign up for the Enhydra mailing list (http://www.enhydra.org/community/mailingLists/index.html). There are a variety of people from around the world on the list, and they are all achieving a fascinating array of different things with Enhydra. There is a really good chance that somebody will be able to answer just about any question you may have. In a way, the community is more than just a list - it's the main technical support center, and also features a searchable archive.