Technology Tales

Adventures & experiences in contemporary technology

java.net.MalformedURLException: unknown protocol: j

15th December 2007

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.

Append or update?

25th November 2007

SAS can generate many types of output: plain text, XML, PDF, RTF, Excel, etc. With all of these and the SAS procedures like PROC REPORT, PROC TABULATE and so on, it might seem surprising for me to say that I have been generating output with data step PUT and FILE statements. There was, of course, a reason for this: creating text files for loading into a new database-driven software application. At one stage, I also did some data interleaving at the output stage and that’s when I discovered that the default behaviour for SAS FILE statements is to completely overwrite a file unless the MOD option was specified. Adding that switches on APPEND behaviour. The code below adds a header in one step while adding data below it in another. I know that there are slicker ways to achieve this like setting up your data as you want it or using _N_ to ensure that something only appears once but here’s another way. As per the Perl, there’s often more than one way to do something with SAS.

data _null_;
file ds_data;
put "fieldtype;datasetname;datasetlabel;datasetlayout;datasetclass;datasetstandardversion";
run;

data _null_;
set ds_ispec;
file ds_data mod;
line="datasetstandard;"||trim(memname)||";"||trim(memlabel)||";;;"||trim(memver);
put line;
run;

Setting up a test web server on Ubuntu

1st November 2007

Installing all of the bits and pieces is painless enough so long as you know what’s what; Synaptic does make it thus. Interestingly, Ubuntu’s default installation is a lightweight affair with the addition of any additional components involving downloading the packages from the web. The whole process is all very well integrated and doesn’t make you sweat every time you to install additional software. In fact, it resolves any dependencies for you so that those packages can be put in place too; it lists them, you select them and Synaptic does the rest.

Returning to the job in hand, my shopping list included Apache, Perl, PHP and MySQL, the usual suspects in other words. Perl was already there as it is on many UNIX systems so installing the appropriate Apache module was all that was needed. PHP needed the base installation as well as the additional Apache module. MySQL needed the full treatment too, though its being split up into different pieces confounded things a little for my tired mind. Then, there were the MySQL modules for PHP to be set in place too.

The addition of Apache preceded all of these but I have left it until now to describe its configuration, something that took longer than for the others; the installation itself was as easy as it was for the others. However, what surprised me were the differences in its configuration set up when compared with Windows. Same software, different operating system and they have set up the configuration files differently. I have no idea why they did this and it makes no sense at all to me; we are only talking about text files after all. The first difference is that the main configuration file is called apache2.conf in Ubuntu rather than httpd.conf as in Windows. Like its Windows counterpart, Ubuntu’s Apache does uses subsidiary configuration files. However, there is an additional layer of configurability added courtesy of a standard feature of UNIX operating systems: symbolic links. Rather than having a single folder with the all configuration files stored therein, there are two pairs of folders, one pair for module configuration and another for site settings: mods-available/mods-enabled and sites-available/sites-enabled, respectively. In each pair, there is a folder with all of the files and another containing symbolic links. It is the presence of a symbolic link for a given configuration file in the latter that activates it. I learned all this when trying to get mod_rewrite going and changing the web server folder from the default to somewhere less susceptible to wrecking during a re-installation or, heaven forbid, a destructive system crash. It’s unusual but it does work, even if it takes that little bit longer to get things sorted out when you first meet up with it.

Apart from the Apache set up and finding the right things to install, getting a test web server up and running was a fairly uneventful process. All’s working well now and I’ll be taking things forward from here; making website Perl scripts compatible with their new world will be one of the next things that need to be done.

Tidying dynamic URL’s

15th June 2007

A few years back, I came across a very nice article discussing how you would make a dynamic URL more palatable to a search engine and I made good use of its content for my online photo gallery. The premise was that URL’s that look like that below are no help to search engines indexing a website. Though this is received wisdom in some quarters, it doesn’t seem to have done much to stall the rise of WordPress as a blogging platform.

http://www.mywebsite.com/serversidescript.php?id=394

That said, WordPress does offer a friendlier URL display option too and you can see this in use on this blog; they look a little like the example URL that you see below, and the approach is equally valid for both Perl and PHP. I have been using the same approach for the Perl scripts powering my online phone gallery and now want to apply the same thinking to a gallery written in PHP:

http://www.mywebsite.com/serversidescript.pl/id/394

The way that both expressions work is that a web server will chop pieces from a URL until it reaches a physical file. For a query URL, the extra information after the question mark is retained in its QUERY_STRING variable while extraneous directory path information is passed in the variable PATH_INFO. For both Perl and PHP, these are extracted from the entries in an array; for Perl, this array is called is $ENV and $_SERVER is the PHP equivalent. Thus, $ENV{QUERY_STRING} and $_SERVER{‘QUERY_STRING’} traps what comes after the “?” while $ENV{PATH_INFO} and $_SERVER{‘PATH_INFO’} picks up the extra information following the file name (the “/id/394/” in the example). From there on, the usual rules apply regarding cleaning of any input but changing from one to another should be too arduous.

Perl vs. PHP: A Personal Experience

11th June 2007

Ever since I converted it from a client-side Javascript-powered affair, my online photo gallery has been written in Perl. There have been some challenges along the way, figuring out how to use hash tables has been one, but everything has worked as expected. However, I am now wondering if it is better to write things in PHP for sake of consistency with the rest to the website. I had a go a rewriting the random photo page and, unless I have been missing something in the Perl world, things do seem more succinct with PHP. For instance, actions that formerly involved several lines of code can now be achieved in one. Reading the contents of a file into an array and stripping HTML/XML tags from a string fall into this category and seeing the number of lines of code halving is a striking observation. I am not going to completely abandon Perl, it’s a very nice language, but I do rather suspect that there is now an increased chance of I having a website whose server-side processing needs are served entirely by PHP.

Photo gallery trouble

4th June 2007

The recent woes at Zooomr (mustn’t forget that it is spelt with three O’s…), have prompted me to ponder photo galleries. My own is a self-hosted affair with Perl doing the honours of reading and processing data stored in an XML file. It may seem a unsophisticated system but it has worked well and, apart from the matter of server administration, I am in full control. Yes, there is a development and maintenance overhead but I enjoy programming and scripting anyway; I just to find the time for it. If this is not your idea of fun, then using a service like Flickr, Zooomr or Photobucket is attractive so long as things don’t go awry as they have for Zooomr and all of the bad publicity and user frustration can’t have done Zooomr’s future prospects any good at all.

A web development toolbox

23rd March 2007

Having been on a web-building journey from Geocities to having a website with my own domain hosted by Fasthosts, it should come as no surprise that I have encountered a number of tools and technologies over this time and that my choices and knowledge have evolved too. I’ll muse over the technologies first before going on to the tools that I use.

Technologies

XHTML

When I started building websites, HTML 4 was not long in existence and I devoured most if not all of Elizabeth Castro’s Peachpit Visual Quickstart guide to the language within a weekend. Having previously used fairly primitive WYSIWYG tools like Netscape Composer and Claris Home Page, it was an empowering experience and the first edition (it is now on its third) of Jennifer Niederst Robbins’ Web Design in a Nutshell took things much further, becoming something of a bible for a number of years.

When it first appeared, XHTML 1.0 wasn’t a major change from HTML 4, but its stricter more XML-compliant syntax was meant to point the way to the future and semantic markup was at its heart at least as much as it was for HTML 4. XHTML 2.0 is on the horizon and after the modular approach of XHTML 1.1 (which I have never used), it will be interesting to see how it develops. Nevertheless, there is a surprising development in that some people are musing over the idea of having an HTML 5. Let’s hope that the (X)HTML apple cart doesn’t get completely overturned after some years of relative stability. I still bear scars from the browser wars raging in the 1990’s and don’t want to see standards wars supplanting the relative peace that we have now. That said, I don’t mind peaceful progression.

CSS

Only seems to be coming into its own in the last few years and is truly an amazing technology in spite of the hobbles that MSIE places on our ambitions. CSS Zen Garden has been a major source of ideas; I wouldn’t have been able to customise this blog as much as I have without them. I was an early adopter of the technology and got burnt by inconsistent browser support; Netscape 4 was the proverbial bête noir back then, fulfilling the role that MSIE plays today. In those days, it was the idea of controlling text display and element backgrounds from a single place that appealed. Since then, I have progressed to using CSS to replace table-based layouts and to control element positioning. It can do more…

JavaScript

Having had a JavaScript-powered photo gallery before my current Perl-driven one, I can say that I have definitely sampled this ever-pervasive scripting language. Being a client-side language rather than a server-side one, it does place you rather at the mercy of the browser purveyors and it never ceases to amaze me that there is a buzz around AJAX because of this. In fact, the abundance of AJAX cross-browser function libraries is testimony to the need for browser-specific code. Despite my preferences for server-side scripting, I still find a use for JavaScript and its main use for me these days is to dynamically control CSS elements to do such things as control the height of a page element or whether it is shown or not. Apparently, CSS may get some dynamic capabilities in the future and reduce my dependence on JavaScript. In the meantime, Jeremy Keith’s DOM Scripting (Friends of Ed) will prove as much of an asset as it has done.

XML

These days, a lot of the raw data underlying my personal website is stored in XML. I did try to dynamically transform the display of the XML into something meaningful with CSS and XSLT when I first scaled its dizzy heights but I soon resorted to other techniques. Browser support and the complexity of what I required were the major contributors to this. The new strategy involved two different approaches. The first was to create PHP/XHTML pages from the precursor XML offline and this is how I generate the website’s directory pages. The other one is to process the XML as text to dynamically supply an XHTML page as the user visits it; this is the way that the photo gallery works.

Perl

This still powers all of my photo gallery. While thoughts of changing it all to PHP linger, there is a certain something about the Perl language that keeps it there. I suppose it is that PHP is entangled in the HTML while Perl encases the whole business and I am reasonably familiar with its syntax these days which is why it still does a lot of the data processing grunt work that I need.

PHP

PHP is everywhere these days, though it doesn’t attract quite the level of hype that used to be the case. It still appears with its sidekick MySQL in many website applications. Blogging software such as WordPress and content management systems like Drupal, Mambo and Joomla! wouldn’t exist without the pair. It appears on my website as the glue that holds my visitor directories together and is the processing engine of my WordPress blog. And if I ever get to a Drupal element to the site, by no means a foregone conclusion though I am spending a lot of time with it at the moment, PHP will continue its presence in my website scripting as it powers that too.

Applications

Macromedia HomeSite

I have a liking for hand coding, so this does most of what I need. When Macromedia (itself since taken over by Adobe, of course) took over Allaire, HomeSite sadly lost its WYSIWYG capability, but the application still soldiers on even though Dreamweaver offers a lot to code cutters these days. Nevertheless, it does have certain advantages over Dreamweaver: it is a fleeter beast to start up and colour codes Perl syntax.

Macromedia Dreamweaver

There was a time when Dreamweaver was solely a tool for visual web page development, but the advent of Dreamweaver UltraDev added server-side development capabilities to the Dreamweaver family. These days, there is only one Dreamweaver version, but UltraDev’s capabilities still live on in the latest version and I would not be surprised if they were taken further in these database-driven times.

Nowadays, Dreamweaver isn’t an application where I spend a great deal of time. In former times, when my site was made up of static HTML pages, I used Dreamweaver a lot even if its rendering capabilities were a step behind the then-current browser versions. I suppose that it didn’t fit the way in which I worked, but its template-driven workflow would have been a boon back then.

However, my move from a static site to a dynamic one, starting with my photo gallery, has meant that I haven’t used it as much since then. However, with my use of PHP/MySQL components on my site. Its server-side abilities could get the level of investigation that its PHP/MySQL capabilities allow.

Altova XMLSpy Professional

Adding MySQL databases to my web hosting costs money, not a lot but it could be spent on other (more important?) things. Hence, I use XML as the data store for my photo gallery and XML files are pre-processed into XHTML/PHP pages for my visitor directories prior to uploading onto the server.

I use XMLSpy to edit and manage the XML files that I use: its ability to view XML in grid format is a killer feature as far as I am concerned and XML validation also proves very useful; particularly with regard to ensuring that DTD’s and XML files are in step and for the correct coding of XSLT files. There are other features that I need to explore and that would also take my knowledge of the XML further to boot, not at all a bad thing.

Saxon

For processing XML into another file format such as XHTML, you need a parser and I use the free version of Saxon to do the needful, Saxonica offers commercial versions of it. There is, I believe, a parser in XMLSpy but I don’t use it because Saxon’s command line interface fits better into my workflow. This is a Perl-driven process where XML files are read and XSLT files, one per XML file, are built before both are fed to Saxon for transforming into XHTML/PHP files. It all works smoothly and updating the XML inputs is all that is required.

AceFTP

If I were looking for an FTP client now, it would be FileZilla but AceFTP has served me well over the last few years and it looks as if that will continue. It does have some extra features over FileZilla: transfers between remote sites, and scheduling, for example. I have yet to use either but they look valuable.

Hutmil

In bygone days when I had loads of static HTML files, making changes was a bit of a chore if they affected every single file. An example is changing the year on the copyright message on the page footers. Hutmil, which I found on a magazine cover-mounted disc, was a great time saver in those days. Today, I achieve this by putting this information into a single file and getting Perl or PHP to import that when building the page. The same “define once, use anywhere” approach underlies CSS as well and scripting very usefully allows you to take that into the XHTML domain.

Apache

Apache is ubiquitous these days and both the online and offline versions of my site are powered by it. It does require some configuration but it is a very powerful piece of kit. The introduction of 2.2.x meant a big change in the way that configuration files were modularised and while most things were contained in a single file for 2.0.x, the settings are broken up into different files in 2.2.x and it can take a while to find things again. Without having it on my home PC, I would not be able to use Perl, PHP or MySQL. Apart from this, I especially like its virtual site capability; very useful for offline development.

WordPress

My hosting supplier offers blogs on Blogware, but that didn’t offer the level of configuration that I would have liked. It is true that this is probably true of any host of blogs. I can’t speak for Blogger but WordPress.com does have its restrictions too. To make my hillwalking blog fit in with the appearance of my photo gallery, I went popped over to WordPress.org to download WordPress so that I could host a blog myself and have maximum control over its appearance. WordPress supports themes so I created my own and got my blog pages looking as if they are part of my website, rather than looking like something that was bolted on. Now that I think of it, what about WordPress supporting user-created themes? I support that there is the worry of insecure PHP code but what about it?

MySQL

I am between minds on whether this is a technology or a tool. SQL certainly would be a technology standard but I am not so clear on what MySQL would be. In any case, I have classed it as a tool and a very useful one at that. It is the linchpin for my WordPress blogs and, if I go for a content management system like Drupal, its role would surely grow. While I do have a lot of experience with using SAS SQL and this helps me to deal with other varieties, there is still a learning curve with MySQL that gets me heading for a good book and Kofler’s The Definitive Guide to MySQL5 (Apress) seems to perform more than adequately in this endeavour.

Paint Shop Pro

As someone who hosts an online photo gallery, it won’t come as a surprise that I have had exposure to image editors. Despite various other flirtations, Paint Shop Pro has been my tool of choice over the years, but it is now set to be usurped by a member of Adobe’s Photoshop family. Paint Shop Pro does have books devoted to it but it seems that Photoshop gets better coverage and I feel that my image processing needs to be taken up a gear, hence the potential move to Photoshop

HennessyBlog theme update

12th February 2007

Over the weekend, I have been updating the theme on my other blog, HennessyBlog. It has been a task that projected me onto a learning curve with the WordPress 2.1 codebase. I have collected what I encountered so I know that it’s out there on the web for you (and I) to use and peruse. It took some digging to get to know some of what you find below. Any function used to power WordPress takes some finding so I need to find one place on the web where the code for WordPress is fully documented. The sites presenting tutorials on how to use WordPress are more often than not geared towards the non-techie rather than code cutters like myself. Then again, they might be waiting for someone to do it for them…

The changes made are as follows:

Tweaks to the interface

These are subtle with the addition of navigation controls to the sidebar and the change in location of the post metadata being the most obvious enhancements. “Decoration” with solid and dashed lines (using CSS border attributes rather than the deprecated hr tagset) and standards compliance links.

Standards compliance

Adding standards compliance links does mean that you’d better check that all is in order; it was then that I discovered that there was work to be done. There is an issue with the WordPress wpautop function (it lives in the formatting.php file) in that it sometimes doesn’t add closing tags. Finding out that it was this function that is implicated took a trip to the WordPress.org website; a good rummage in the wp-includes folder does a lot but it can’t achieve everything.

Like a lot of things in the WordPress code, the wpautop function isn’t half buried. The the_content function (see template-functions-post.php) used to output blog entries calls get_content function (also in template-functions-post.php) to extract the data from mySQL. The add_filter function (in plugin.php) associates the wpautop function and others with get_the_content function and the p tags get added to the output.

To return to the non-ideal behaviour that caused me to start out on the above quest, an example is where you have an img tag enclosed by div tags. The required substitution involves the use of regular expressions that work most of the time but get confused here. So adding a hack to the wpautop function was needed to change the code so that the p end tag got inserted. I’ll be keeping an eye out for any more scenarios like this that slip through the net and for any side effects. Otherwise, compliance is just making sure that all those img tags have their alt attributes completed.

Tweaks to navigation code

Most of my time has been spent on tweaking of the PHP code supporting the navigation. Different functions were being called in different places and I wanted to harmonise things. To do this, I created new functions in the functions.php for my theme and needed to resolve a number of issues along the way. Not least among these were regular expressions used for subsetting with the preg_match match that weren’t to my eyes Perl-compliant, as would be implied by the choice of function. I have since found that PCRE’s in PHP use a more pragmatic syntax but there remained issues with the expressions that were being used. They seemed to behave OK in their native environment but fell out of favour within the environs of my theme. Being acquainted with Perl, I went for a more familiar expression style and the issue has been resolved.

Along the way, I broke the RSS feed. This was on my off-line test blog so no one, apart from myself, that is, would have noticed. After a bit of searching, I realised that some stray white-space from the end of a PHP file (wp-config.php being a favourite culprit), after the PHP end tag in the script file as it happens, was finding its way into the feed and causing things to fall over. Feed readers don’t take too kindly to the idea of the XML declaration not making an appearance on the first line of the file. The refusal of Firefox to refresh things as it should caused some confusion until I realised that a forced refresh of the feed display was needed -- sometimes, it takes a while for an addled brain to think of these kinds of things.

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