Feeds

Groovy: XML without the bloat

Flexible strings

Top 5 reasons to deploy VMware with Tegile

Hands on, part 1 You may find this hard to believe, but there was a time before XML hell, when the idea was that XML was going to solve just about every tricky problem in software development. From swapping data between applications or platforms, to storing complex data structures in a portable format - XML was the answer.

Growing up around the same time as XML was Java, which - like XML - has since gone on to shape an industry. If we’re honest, though, it’s never been an easy relationship between these two. Processing XML in Java is a common enough requirement, but it can be extremely verbose, requiring plenty of boilerplate code and all kinds of extraneous scaffolding that obscures what are often very straightforward functions.

That’s where Groovy comes in. As befits a young scripting language for the Java Virtual Machine, Groovy can do XML in a way that is relatively free of bloat and allows the developer to focus on the real problem at hand. In this two-part tutorial I shall look at how Groovy can help in reading and writing XML documents. You can find instructions on installing and running Groovy here, or you can refer back to my earlier article.

At some time or other we’ve probably all written code that just uses strings to write out a fragment of XML. It’s cheap but clunky, but it saves having to instantiate a DOM tree or any of that fiddly stuff. Groovy’s flexible strings allow us to do this very, very simply.

Here’s how we create a fragment of XML that contains a list of names each in an element called "hello", and each with an order attribute:

names=['john','bill','ted']
x=0
frag=''
names.each {
  x++
  frag+="""<hello order="$x">$it</hello>\n"""
}

Running this code in the GroovyConsole, or dumping it into a file called xml.groovy and running it from the command line produces the following output:

<hello order="1">john</hello>
<hello order="2">bill</hello>
<hello order="3">ted</hello>

But that’s only a bunch of strings, there’s no XML declaration, and certainly no way it can be processed as XML. If we do need to turn this into a DOM tree, we can do that easily enough too. Let’s make our hello elements children of a root element called "names" and then turn it into a DOM tree that we can interrogate:

def StringReader s=new StringReader("<names>\n" + frag + "</names>")
def xmldoc=groovy.xml.DOMBuilder.parse(s)
def names=xmldoc.documentElement

println names 

use (groovy.xml.dom.DOMCategory){
    println names.hello[0].text()
    println names.hello.size()
    println names.hello[1].attributes.item(0).text()
}

This code spools out our well-formed XML and the results of some simple tree walking:

<?xml version="1.0" encoding="UTF-8"?>
<names>
<hello order="1">john</hello>
<hello order="2">bill</hello>
<hello order="3">ted</hello>
</names>

john
3
2

It should be clear by now that the combination of Groovy’s convenience methods (from the groovy.xml.* libraries), iterators and powerful string handling capabilities make for very succinct code for creating XML from relatively straightforward data. While the equivalent Java code would take a lot more typing - which wouldn’t be half as readable and easy to follow - so far there’s nothing tremendously taxing here.

Intelligent flash storage arrays

More from The Register

next story
Be real, Apple: In-app goodie grab games AREN'T FREE – EU
Cupertino stands down after Euro legal threats
Download alert: Nearly ALL top 100 Android, iOS paid apps hacked
Attack of the Clones? Yeah, but much, much scarier – report
Microsoft: Your Linux Docker containers are now OURS to command
New tool lets admins wrangle Linux apps from Windows
Bada-Bing! Mozilla flips Firefox to YAHOO! for search
Microsoft system will be the default for browser in US until 2020
Facebook, working on Facebook at Work, works on Facebook. At Work
You don't want your cat or drunk pics at the office
Soz, web devs: Google snatches its Wallet off the table
Killing off web service in 3 months... but app-happy bonkers are fine
prev story

Whitepapers

Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
How to determine if cloud backup is right for your servers
Two key factors, technical feasibility and TCO economics, that backup and IT operations managers should consider when assessing cloud backup.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Protecting against web application threats using SSL
SSL encryption can protect server‐to‐server communications, client devices, cloud resources, and other endpoints in order to help prevent the risk of data loss and losing customer trust.