Obviously, I've been playing around with XSLT lately. So naturally, the next logical step was to delve into , the XML query language de jure. Eventually I want to run queries on MusicXML documents, but I need to start small.
While the W3Schools tutorial on XQuery is a great introduction, there's one little problem.
It doesn't really tell you how to implement : i.e. how to actually run a query and retrieve results.
So after some random perusing and downloading, I - like the fool I am – was made aware by Dr. Michael Kay's "Learn in 10 Minutes: An Tutorial" that the Saxon XSLT processor I was already using for XSLT transformations already had an engine built in.
That's to say that the .NET version of Saxon has 2 command line executables:
- Transform.exe, which I'd already used for XSLT transformations
- Query.exe, which allows one to run queries
So much for paying attention to what I download …
From there, it was a simple matter to use for the first time.
Here are the steps:
- I downloaded the books.xml file provided by W3Schools and place it into the "bin" directory of Saxon on my drive. This is same directory where the 2 afformentioned executables reside.
- Using the kick-tail text editor jEdit, I copy/pasted/saved this query example from the W3Schools as "test." (also saved in the "bin" directory):
<ul>
{
for $x in doc("books.xml")/bookstore/book/title
order by $x
return <li>{data($x)}</li>
}
</ul>
This query simply lists all the titles from "books.xml" in alphabetical order.
- Then using jEdit's command line plug-in called "Console", I set Console to the Saxon "bin" directory where "query.exe", "books.xml", and "test." reside. The easiest way to set the directory in Console is to type:
cd "C:\Documents and Settings\nitin\Desktop\saxon\bin"
Of course, you might extract Saxon elsewhere, but the important thing is to type cd + opening quotation mark + full path to Saxon's "bin" folder + ending quotation mark.
- Now I was in the correct folder and could run the with the following command line syntax:
query test.
And my results look like this:
I know what you're thinking: no line breaks! Sure, the computer doesn't care, but this is really hard for humans to read!
Yes, that's true. But I went ahead and pasted the following:
<?xml version="1.0" encoding="UTF-8"?><ul><li>Everyday Italian</li><li>Harry Potter</li><li>Learning XML</li><li> Kick Start</li></ul>
into a new document in jEdit anyway.
We're gonna take care of those line breaks now …
- One of the many great things about jEdit is the ability to run Beanshell commands, which despite my attempts to sound authoritative, I only learned about roughly 30 minutes ago. This means that a search and replace can be done in jEdit using simple Java syntax to fix that line break issue. The first step is identifying where to insert the line break. I needed it in between > and <. Specifically, I needed a line break between all the red and green colored brackets:
<?xml version="1.0" encoding="UTF-8"?><ul><li>Everyday Italian</li><li>Harry Potter</li><li>Learning XML</li><li> Kick Start</li></ul>
So I just invoked the jEdit search/replace box and did the following:
This simply says:
Find all instances of
><
and
Replace it with
>
<
- i.e. the text between the quotation marks. The n is, by the way, the line break syntax.
When I hit "Replace All", this was the result:
<?xml version="1.0" encoding="UTF-8"?>
<ul>
<li>Everyday Italian</li>
<li>Harry Potter</li>
<li>Learning XML</li>
<li> Kick Start</li>
</ul>
Problem solved.
- Now I simply saved this document as "test.html" and opened it in a browser.
Anyway, that's my very simple start to , but I'm feeling pretty good about it nonetheless.
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