I know that that there better things to call a blog post than to use part of an error message that I got from Saxonica‘s Saxon while I was converting XML files into PHP equivalents for the visitor information section of my main website. I use the open source Saxon-B rather than the commercial Saxon-SA and it fulfils all of my needs and version 8 and later (it has now reached 9.0.0.2) handle the XSLT 2.0 features that I need to make the transformations really clever. Also, because Saxon is available as a jar file, it is cross platform so long as you have Java on board. There are, however, some slight differences in behaviour. I now run thte thing in Linux and any Windows-style file locations are not recognised. I had the file path in a DTD declaration starting with "J:\" and that was thought to be a protocol like file, http, https, ftp and so on because of the colon. There’s no j protocol so Java gets confused and, voilà!, you get the rather obscure error that titles this post. Otherwise, the migration of the Perl script that creates XSLT files and fires off the required XML to PHP transformations was a fairly straightforward exercise once file locations and shebang line were set right.
Tag Archive for XSLT
java.net.MalformedURLException: unknown protocol: j
Exploring AJAX
When I first started it, my online photo gallery started out simply as a set of interlinked HTML pages. Over time, I discovered frames (yes, them!) and started to make use of JavaScript to make the slideshows slicker. In those days, I was working off free webspace provided by my ISP and client-side scripting was the only tool that I had for enhancing functionality. Having tired of the vagaries of client-side scripting – the browser wars were in full swing and incompatibilities reigned supreme, I went with paid hosting in order to get access to tools like Perl and PHP for server-side processing; their flexibility compared to JavaScript was a breath of fresh air to me and I am still a fan of the server-side approach.
The journey that I have just described is one that I now know was followed by a lot of website builders around the same time. Nevertheless, I have still held onto JavaScript for some things, particularly for updating the DOM as part of making the pages more responsive to user interaction. In the last few years, a hybrid approach has been gaining currency: AJAX. This offers the ability to modify parts of a page without needing to reload the whole thing and that has generated a considerable amount of interest among web application developers.
The world of AJAX is evidently a complex one though the underlying principle can be explained in simple terms. The essential idea is that you use JavaScript to call a server-side script, PHP is as good an example as any, that returns either text or XML that can be used to update part of a web page in situ without the need to reload it as per the traditional way of working. It has opened up so many possibilities from the interface design point of view that AJAX became a hot topic that still receives much attention today. One bugbear is efficiency because I have seem an AJAX application lock up a PC with a little help from IE6. There will always remain times where server-side processing is the best route and that needs to balanced against the client-side and vice versa.
Like its forbear DHTML, AJAX is really a development approach using a number of different technologies in combination. The DHTML elements such as (X)HTML, CSS, DOM and JavaScript are very much part of the AJAX world but server-side elements such as HTTP, PHP, MySQL and XML are also very much part of the fabric of the landscape. In fact, while AJAX can use plain text as the transfer format, XML is the one implied by the AJAX acronym and XSLT is used to transform XML in HTML. However, AJAX is not limited to the aforementioned technologies; for instance, I cannot see why Perl cannot play a role in place of PHP and ASP can be used for the same things.
Even in these standards-compliant days, browser support for AJAX remains diverse, to say the least, and it is akin to having MSIE in one corner and the rest in the other. Mind you, Microsoft did introduce the tools in the first place but they used ActiveX and Mozilla created a new object type rather than continue this method of operation. Given that ActiveX is a Windows-only technology, I can see why Mozilla did what they did and it is a sensible decision. In fact, IE7 appears to have picked up the Mozilla way of doing things.
Even with the apparent convergence, there will continue to be a need for the AJAX JavaScript libraries that are currently out there. Incidentally, Adobe has included one called Spry with Dreamweaver CS3. Nevertheless, I still like to find out how things work at the basic level and feel somewhat obstructed when I cannot do this. I remember perusing Wrox’s Professional AJAX and found the constant references to the associated function library rather grating; the writing style didn’t help either.
My taking a more granular approach has got me reading SAMS Teach Yourself AJAX in 10 Minutes as a means for getting my foot in the door. As with their Teach Yourself … in 24 Hours series, the title is a little misleading since there are 22 lessons of 10 minutes in duration (the 24 Hours moniker refers to there being 24 lessons, each of one hour in length). Anything composed of 10 minute lessons, even 22 of them, is never going to be comprehensive but, as a means for getting started, I have to say that the approach seems effective on the basis of this volume. It has certainly whet my appetite for giving AJAX a go and it’ll be interesting to see how things progress from here.
Open source CMS options
After reading an article in the latest issue of PC Plus, I got curious about the world of content management systems again. I went over to OpenSourceCMS to sample the CMS demos that they have got on there. Mambo and Joomla! are fully fledged CMS’s and look impressive too, though how they would fit into my online presence is something of an open question. I spied that PHP-Nuke uses themes so that is an attraction; I am already used to that mindset thanks to WordPress. Drupal seems to be less slick than the others but that could be an attraction of itself; it does offer themes but no rich text editing is available.
All of the above are base upon PHP/MySQL but I ignored them for some reason when I last took a look at open source CMS’s. That does seem a strange thing to do but this was a while ago and the moderate cost of adding database functionality to my website was not something that I was willing to pay, though I have done so since for HennessyBlog. I therefore ended up taking a look at Plone (built on Zope and using the Python programming language). What I was had in mind at the time was a replacement for Perl-powered photo gallery and a CMS was never going to fit the bit; it still doesn’t. In any case, I like coexistence of website components on a single server and Plone left me with the impression that it was an all or nothing affair. Things may have changed since so giving it another go remains an option.
I have now decided to take a look at Drupal but the emphasis this time is not on using it as a photo gallery platform; if I wanted that, I’d go with the API for something like Flickr or Zooomr. This time, the emphasis on using a CMS to manage the visitor information directories on my website. It does coexist with the other website components, including WordPress and the aforementioned bespoke built photo gallery. Interestingly, Drupal does offer blogging functionality if I wanted it.
Set up involved a spot of work with mySQL before moving onto other things:
mysql -u adminuserid -p /* logging in*/
create database drupal; /*creating new database*/
grant ALL on drupal.* to adminuser identified by “**********” /* granting access to new database */
quit; /* exiting */
I prefer command line working with mySQL; it is easier to see what’s going on (not wrong, hopefully). For some reason, Drupal comes only in tar.gz archives but I extracted this into the web server directory and opened up the site in Firefox. Installation only requires set up of database access and is very quick. A few things turned up in the status report that needed attention: cron, this can be run manually; activation of PHP Unicode and GD library (PHP’s gd_info function is a real help in testing this) extensions, editing of php.ini to remove commenting semicolons activated them and restarting Apache made them available; having a place to store uploads, the directory files was created.
I have since set about bending it to my will, not always an easy thing to do with software. The first thing to do was to give it a static home page. By default, Drupal places tasters for any nominated pages and stories on its home page and shows configuration instructions until you allow some content to filter through. However, adding the Front Page module allows you to override this behaviour and have something more static. It was an entry on Kehan’s Blog that set me heading in the right direction.
The next steps are be to persuade the thing to allow external links to exist in menus (patches exist but I have yet to learn how to apply them other than finding the nefarious piece of code and replacing, a considerable challenge that makes me wonder if there is not a better way to do it: with a module, perhaps?) and carry on the theme editing until it ties in with the rest of my site. Then, I’ll make the decision as to whether to replace my current work flow (Perl-powered pre-processing of XML into PHP/XHTML using XSLT and the Saxon parser followed by FTP upload to the web server) with this one. The automation of the former argues in its favour. We’ll see how things pan out…