Using PerlSAX

Working with PerlSAX involves using two classes (packages), a PerlSAX parser that generates parsing events and a class that you write that will receive those parsing events, the ``handler''. This guide will use the XML::Parser::PerlSAX parser that uses Clark Cooper's XML::Parser module.

The handler class implements the PerlSAX handler methods that you are interested in. The following example, MyHandler.pm, prints a message every time an element starts or ends: 

    package MyHandler;


    sub new {
        my ($type) = @_;
        return bless {}, $type;
    }


    sub start_element {
        my ($self, $element) = @_;


        print "Start element: $element->{Name}\n";
    }


    sub end_element {
        my ($self, $element) = @_;


        print "End element: $element->{Name}\n";
    }


    1;

To use your handler you will need to have a script, myhandler.pl, that loads and creates your handler and the parser, and then calls the parser to parse the XML instance and send events to your handler: 

    use XML::Parser::PerlSAX;
    use MyHandler;


    my $my_handler = MyHandler->new;
    my $parser = XML::Parser::PerlSAX->new( Handler => $my_handler );


    foreach my $instance (@ARGV) {
        $parser->parse(Source => { SystemId => $instance });
    }

Given this XML instance, myhandler.xml: 

    <?xml version="1.0"?>


    <article>
    <title>Using PerlSAX</title>
    <paragraph>Working with PerlSAX ...</paragraph>
    </article>

Running myhandler.pl like this: 

    perl myhandler.pl myhandler.xml

will produce this output: 

    Start element: article
    Start element: title
    End element: title
    Start element: paragraph
    End element: paragraph
    End element: article

For More Information

PerlSAX.pod describes the PerlSAX interface. Each parser module describes it's individual capabilities. XML::Parser::PerlSAX is the most commonly used PerlSAX implementation.

The files described in this doc are in the `examples' directory. A more complete implementation of the very simple handler above is in the module XML::Handler::Sample. Other, more complex handlers are in the XML::Handler directory as well.

Another hands-on doc for PerlSAX is the XML-Parser-and-PerlSAX.pod. This doc describes the difference between and the purpose of PerlSAX with respect to XML::Parser.

This document was inspired by and uses the code examples from David Megginson's ``Quick Start for SAX Application Writers.'' <http://www.megginson.com/SAX/quickstart.html>