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Using Gravatars in Unify

Republished because of my weird fixation on everything having to last forever

Dealing with complex data types in XSL

My motivation for creating this article comes from wanting to implement Gravatars on a blog/comment feature on a Unify site. To create a link to a Gravatar you need to generate a URL that contains an MD5 hash of an email adress in HEX formatting and XSL simply doesn't help much with that sort of thing. In Java code however generating an MD5 hash from an email address is a trivial task.

VYRE Unify uses XSL a lot to generate HTML from the XML data stored in it's content repository. This can often lead to issues for users trying to produce output with anything more complicated than plain text with simple HTML tags and URLs. For example reformating dates is a nightmare to do with just plain XSL and XPath.

This is where XSL Java extensions come in to save the day. Using XSL Java extensions you can effectively call any Java method available from an XSL script. VYRE Unify fully supports XSL Java extensions.

To explain what XSL Java extensions are, here is a simple example that prints the cosinus of a number in the XML source.

To explain what's going on here, I have defined a new namespace “math” to be a Java class format namespace. I can then call static methods on that class in XPath by using the namespace. Note the parameter is a XPath that resolves to a tag containing a number and is automatically cast to a javatype double.

A slightly more complicated example would be printing the current date:

<xsl:template name="currentDate" xmlns:date="xalan://java.util.Date"> <xsl:variable name="current-date" select="date:new()" /> <xsl:value-of select="date:toString( $current-date )" /> </xsl:template>

This is the equivalent of the Java code:

public String getCurrentDate() { java.util.Date currentDate = new java.util.Date(); return currentDate.toString(); }

You might notice that the method calls in the XPath look a bit backward compared to the Java syntax. The rule is a methods declaring class is the first parameter of the method and the following parameters are the Java methods parameters. Calling constructors is the same syntax as calling a static method with the name "new".

Both the examples above use so called Class format namespace, there is also package format namespace and Java format namespace that you can read about in the Xalan documentation.

Using gravatars

Now finally I'll show how I managed to create gravatar links in an item list XSL in Unify. The first place to look was the Gravatar implementor's guide Java section. Where they show a class that can generate the MD5 hash with a simple static method call. What I actually did was cheat, because I knew there was a class in Unify that does exactly the same thing, so I did:

<div xmlns:hasher="xalan://vyre.realms.PasswordService"> <xsl:variable name="hasher" select="hasher:getInstance('MD5', 'hex')"/> <img> <br /> <xsl:attribute name="src"><br /> http://www.gravatar.com/avatar/<xsl:value-of select="hasher:encrypt($hasher, ./creator/email)"/>.jpg </xsl:attribute> </img> </div>

But for non Unify developers it is trivial to compile the class given on the Gravatar site, put it on your Unify servers classpath and calling it like so:

<div xmlns:md5="xalan://MD5Util"> <img> <xsl:attribute name="src"> http://www.gravatar.com/avatar/<xsl:value-of select="md5:md5Hex( ./creator/email )"/>.jpg </xsl:attribute> </img> </div>

Better practices

In the examples above I define the xml namespaces in the outermost tag of the example, this has an annoying side effect of making the xmlns attribute appear in the html output. This can be avoided by defining the namespace in the xsl:stylesheet tag and adding the namespace to xclude-result-prefixes to the xsl:stylesheet tag.

In general you would also usually want to keep this sort of complicated XSL code in separate includable XSL scripts in callable named templates supported in Unify 4.4+.

Das Kapital

“Owners of capital will stimulate the working class to buy more and more of expensive goods, houses and technology, pushing them to take more and more expensive credits, until their debt becomes unbearable. The unpaid debt will lead to bankruptcy of banks, which will have to be nationalised, …”

-- Karl Marx in Das Kapital published 1867 source

Pro blogger

I've finally, after this minimal amount of training, gone pro in my blogging career. My first attempt at pro blogging is this quick overview of my trip to Belgium last year. Expect more to come soonish, so watch this space!

Generic and special laws of laptop relativity

The Atlassian blog just published an theory on Laptop Relavitity. This law, which I have observed myself, is exactly why I think coders should not use laptops for coding. Since desktops rarely have much velocity they are much less affected by the general relativity law, and never by special relativity because public transport workers never let people on the train with a desktop. Especially not if it's as big as mine.

DataMarket

I just bumped into DataMarket, a Icelandic company specializing in custom data aggregation. The concept of a company selling data aggregation as it's product, and buying raw data feeds as raw material somehow makes perfect sense to me. The "Damn, why didn't I think of that." moment made me want to blog.

I also need to get into the habit of blogging since I'll be going pro soon.

Wiki wiki!

For those of the three of you who haven't...

Financial expert

There is a short interview with yours truly on page 4 of Fréttablaðið today, here is the web version. For those who don't understand the language, I'm making huge claims about the everlasting friendship between Britain and Iceland. The reporter seemed to think Icelanders have some reason to fear going to Britain because some Icelandic banks lost British money.

Javascript brainfuck interpreter

Last night I wrote a javascript brainfuck interpreter. You can try it out.

It works by reading the brainfuck code from the textarea and compiling it to the equivalent javascript code. That output is then passed to eval(). The input and output are put into arrays of javascript numbers. The string to/from byte array conversion is done before and after evaluating the program.

As far as I can tell my compiler meets brainfucks official portability standard. It should be a good testing platform for those crazy enough to want to write brainfuck programs, but to lazy to install a compiler.

Google Chrome crash window

Just bumped into this. Nice and quirky:

I'm not sure exactly what I did to cause this. I simply browsed a few pages and then left it running for a few hours.

My pet peeve

I'm hugely annoyed by people that put a space before question marks at the end of questions in languages other than French. Usage of question marks seems have at least three different types, illustrated below.

• ¿Habla Español?
• Parlez-vous français ?
• Do you speak English?
• Talar þú íslensku?

Internet confectionary

It may interest the Icelandic reader of this blog that Gommit & co. have recently launched the Icelandic digg equivalent.

Egoblog

I've noticed when egobrowsing Google Analytics that for some reason this page gets a lot more hits that my amazing mobile blog.

The mobile blog generally has a lot more activity with up to 12 posts per month, so I'd like to recommend it's atom feed to both you syndicators out there.

Money

I recommend watching all 5 parts of this documentary about where money comes from.

Comeback

And with the local BBC news Osama Bin Laden with a triumphant comeback , said the following in his new video:

Dont call it a comeback
I been here for years
Rockin my peers and puttin suckas in fear
Makin the tears rain down like a mon soon
Listen to the bass go boom
Explosion overpowerin
Over the competition Im towerin
Wreckin shop when I drop these lyrics thatll make you call the cops
Dont you dare stare, you betta move
Dont ever compare
Me to the rest thatll all get sliced and diced
Competitions payin the price

Migrating monkeys

I had to migrate from one PC to another slightly newer one at work. After being extremely frustrated about Outlook 2007 not being able to pick up what my setup was on the newer PC I did some googling and found the USMT. The User State Migration Tool will with an amazingly good command line interface (for M$) gather your user settings on one Windows box and restore them on the newer one. I've yet to find anything it missed. You can get the USMT here.

Google webmasters tools

I've decided to share my superb experience with Googles webmaster tools. Apart form having a name that makes me feel like I'm the master of something, it manages to fully serve all my egobrowsing needs. It actually shows a list of all other websites that link to mine, and I can download the information as csv.

Fancy features

I've added a fancy feature to the site. Now the posts on my mobile blog are mirrored here by transforming the Atom feed from blogspot.com via xsl.

Website launch

I've had this domain for a while now and always intended to start a personal/professional blog here. Finally now I have access to a instance of VYRE Unify to play around with so now the only thing that can possibly stop me is finding the time away from making Unify to use it to blog.