I’ve been doing a little more work with Groovy lately, and it still continues to impress me on how expressive and easy some things are to do in this language. Last night I was working with a web service that returns XML and I needed to parse this XML response and do some work with it. Talk about easy! So now I’m going to show you a small example of parsing an XML document of movies, and we’ll display some movie information in the console. The purpose: to see how simple it is to manipulate and read XML documents in Groovy!

<movies>
    <movie name="The Matrix">
        <year>1999</year>
        <directors>
        <director name="Andy Wachowski" />
        <director name="Lana Wachowski" />
        </directors>
        <plotsummary><![CDATA[A computer hacker learns from mysterious rebels about the true nature of his reality and his role in the war against the controllers of it.]]></plotSummary>
    </movie>
    <movie name="Kill Bill: Vol. 1">
        <year>2003</year>
        <directors>
        <director name="Quentin Tarantino" />
        </directors>
        <plotsummary><![CDATA[The Bride wakes up after a long coma. The baby that she carried before entering the coma is gone. The only thing on her mind is to have revenge on the assassination team that betrayed her - a team she was once part of.]]></plotSummary>
    </movie>
</movies>

So that XML above is what we will be working with. A simple document that has a series of movie nodes. Each movie node has an attribute for the name of the movie, followed by nodes that give us a plot summary, the year the movie was released, and a list of directors. The following code sample will show us how we can display the number of movies we have in the document, as well as list each movie’s name, followed by the plot. Let’s see that now.

class groovyXmlParsing  {
    static main(args)  {
        def xmlFileContents = new File("C:\\code\\groovyXmlParsing\\movies.xml").text;
        def movies = new XmlSlurper().parseText(xmlFileContents);

        /*
         * Show how many moves we have in the document
         */
        println "Number of movies: ${movies.movie.size()}\n";

        /*
         * Display the titles and plot for each movie.
         */
        movies.movie.each { movie ->
            println "Movie: ${movie.@name}";
            println "Plot: ${movie.plotSummary.text()}";
            println "";
        };
    }
}

Yes… that’s it! Let’s break it down a bit. The first bit of code is Groovy’s way of reading a text file using the File class. The next line is the fun one. Using the class XmlSlurper we can parse the text into a searchable, workable XML object. And it has a cool name!

From here we display the number of movies that are in the XML document. How? The variable movies represents the XML document, and more importantly is the root node, movies. So with that in mind we now know we can reference additional nodes under movies, and we do this using DOT notation. movies.movie.size() is asking Groovy to get all movie nodes that are children of the root node movies. The size method simply returns the number of elements that match that node’s name.

Ok, but how are we displaying each movie? By using Groovy’s powerful iteration constructs we can, once again, select the movie nodes under root, and call the each method against it. The each method executes a closure, passing in each matched item, usually as a variable named it. I have told Groovy to use a different variable name, however, by specifying it with movie ->. This means the variable movie will contain the current movie node for each node that matches. Effectively this is a loop (did I mention I love Groovy??).

Once inside this closure we can reference attributes and child nodes of each movie node that is given to us during each iteration. And get this! To access attributes on a node, all you have to do is use DOT notation, followed by the name of the attribute prefixed with the AT (@) symbol! Cool!

So I hope this gets some folks excited about learning more about languages, and Groovy in particular! Cheers, and happy coding!