I could not find a cheap hosting service for Java and besides, a friend had recently send me a movie about Web application development. Though this movie is very long it is a funny account of where technology can go wrong. It compares different web development technologies like J2EE, Zope, Ruby on Rails, etc. J2EE comes out rock bottom on all measured scales because of the highly complex configuration and the many XML “situps”. The movie had made it abundantly clear that J2EE was not the technology to go for a tiny school’s web site.
The most popular technique available is likely PHP. PHP is a language that gets executed on the server side. The processor there parses a file that ends with “.php”. These files consist partly of HTML and partly of PHP code. PHP code is signaled with a “<?php” instruction and ends with “?>”. PHP makes it easy to do simple things, unlike some other environments we all know. I found an interesting program on the web that contained a PHP web server and MySQL lite. When started, it serves on port 800 a set of pages from the directory where it started from. That made it easy to test the web site on my own computer. I just need a web site where the navigation bar is maintained in a single file so that changes do not require an update of all other pages. This is easy to do with PHP using includes. The language is supported on every hosting service and there are lots of code snippets on the net that can be “borrowed”.
Sounds all good … Well, it means you have to learn a new language and that is always excruciatingly painful. The syntax is not such an issue nowadays, most languages look similar on that level. However, the libraries are where the pain is. You constantly have to search for code snippets to find out how the functions you are looking for are called. Something I can do in 5 minutes in Java takes me half an hour in PHP because I cannot use my Java experience. Despite these obstacles, it was surprisingly easy to get the site up and running. Developing, and thus debugging, the site was surprisingly easy. You never have to compile and build. Just change the text in Notepad, save and refresh your browser. Though this style does not work well for large systems, it works surprisingly well for simple applications. It is so simple, that my wife can now maintain most of the web site because the text pages have only a boilerplate PHP.
Now, as a husband I was properly rewarded with an impressed wife. As the OSGi evangelist I was on edge. I have made lots of small web sites with OSGi because the Http Service provides excellent Servlet support. I have tried most libraries but never found a library that really made it as easy (and as pleasant) as PHP did. Now OSGi is an open environment so what are the changes of hosting PHP inside an OSGi system? Then again, PHP works so well not because the language is great (it isn’t), but because it strikes the correct balance between HTML coding and programming. I then had to think of Beanshell. Beanshell is a Java interpreter that accepts a simpler syntax of Java as well that is on par with PHP. It does not need types, though it does accept them. The good news (for me) about Beanshell is that I can use the Java libraries. It blends seamlessly with the Java environment. So last night I decided to see if I could make this idea work. Use Beanshell as PHP. I decided to use the same structure as PHP. So a hello world would look like:
<?bsh print( “Hello world at ” + new Date() ); ?>
This turned out to be surprisingly easy. Partly because I already had a small bundle that served files from the file system. It uses configuration admin to match a directory to a path on the web site (can be found on “/web/admin” which is a bit too big a name for what it does). I changed this bundle to register a servlet that would parse any .bsh file, extract the Beanshell code, and merge the HTML and Beanshell execution into the Servlets output. Before the script is executed, I set the Bundle Context, the Http Servlet Request and Http Servlet Response. This gives you full access to the OSGi environment.
Currently the program reads the files from disk, however, there is no reason why it could not read the files from the JAR resources. You develop the pages quickly using the file system and then store them in the JAR before delivery.
I guess by spending the rest of the Sunday behind my computer I have consumed a significant part of the goodwill I had won with my wife … Then again, this was a cool exercise! It is really nice to be able to combine the easy programming model of a script language with the power of a full blown OSGi/Java system. No more PHP jealousy!
If you have too much time and want to play with the prototype, feel free to download it. It is a prototype, so do not expect too much. It should also be clear that this is a personal toy and has no official status. The JAR also contains the sources. There is a small admin console on the http://localhost: