How
to Build a Simple XML Parser Xml:
: Parser is built on top of the Expat XML processing library written by James
Clark XML : : parser is a vital component of XML processing under Perl because
most other modules within Perl use the facilities offered by XML : : Parser to
support their own processing.
_______________________________________________
_______________________________________________
XML
: : Parser itself is an event-based parser, and because it uses the Expat libraries,
it also offers simple validation of your XML documents for well-formedness, although
it doesn’t validate your documents against a DTD. The
interface to the parser is simple; You create a new XML : : Parser object, a suite
of functions that are called when the parser determines a start, end, or data
protion in your XML document. For example, the code in Listing 14.1 builds a very
simple XML parser to output the start and end tags in a document. Listing
14.1: A Simple XML Parser
Use XML : : Parser;
My $parse= new XML : : Parser();
$parse
-> setHandlers ( Start => \&handler-start,
End => \&handler-end,
);
$parse->parsefiles ($file);
sub handler-start
(
my ( $parser,
$element, %attr) =@-;
print “start: $element\n”;
)
sub handler-end
(
my
($parser, $element) =@-;
print “End; $element\n”;
)
Running
this on a simple XML document results in the following output :
$ perl exxmlp.pl
simple.xml
Start: simple
Start: paragraph
End: paragraph
End: simple As
you can , the sample outputs a list of the start and end tags.Because we “register
“ the fungtions that we want to call when different elements are seen, the
functions can be called anything we like. Note
as well that the sfunctions are supplied with the name of the tag that was found
and the list of attributes for a given tag. We can use this information within
the parsing process to be more explicit about the information we pass on. Using
XML : : Parser to Convert to HTML Being
an event-based parser, the XML : : Parser module is ideal in situations where
you need to extract or convert those elements into anotherform . Converting an
XML document into an HTML format for display on screen is a good example. We”re
going to be looking at a CGI script that I wrote on behalf of a client who wanted
tto convert an XML document into HTML for displaying on its Web site. The documents
themselves were a mixture of XML and some HTML components, and you can see a sample
in Listing 14.2 Listing
14.2: A Sample Review Document
<video>
<main>
<title>Alien
Resurrection</title>
<para>Sigourney Weaver, Winona Ryder</para>
<title>Witness
the Resurrection</title>
<para>The review..</para>
</main>
<panel> Xml:
: Parser is built on top of the Expat XML processing library written by James
Clark XML : : parser is a vital component of XML processing under Perl because
most other modules within Perl use the facilities offered by XML : : Parser to
support their own processing. XML
: : Parser itself is an event-based parser, and because it uses the Expat libraries,
it also offers simple validation of your XML documents for well-formedness, although
it doesn’t validate your documents against a DTD. The
interface to the parser is simple; You create a new XML : : Parser object, a suite
of functions that are called when the parser determines a start, end, or data
protion in your XML document. For example, the code in Listing 14.1 builds a very
simple XML parser to output the start and end tags in a document. Listing
14.1: A Simple XML Parser
Use XML : : Parser;
My $parse= new XML : : Parser();
$parse
-> setHandlers ( Start => \&handler-start,
End => \&handler-end,
);
$parse->parsefiles ($file);
sub handler-start
(
my ( $paser,
$element, %attr) =@-;
print “start: $element\n”;
)
sub handler-end
(
my
($parser, $element) =@-;
print “End; $element\n”;
)
Running
this on a simple XML document results in the following output :
$ perl exxmlp.pl
simple.xml
Start: simple
Start: paragraph
End: paragraph
End: simple As
you can , the sample outputs a list of the start and end tags.Because we “register
“ the fungtions that we want to call when different elements are seen, the
functions can be called anything we like. Note
as well that the sfunctions are supplied with the name of the tag that was found
and the list of attributes for a given tag. We can use this information within
the parsing process to be more explicit about the information we pass on. Using
XML : : Parser to Convert to HTML Being
an event-based parser, the XML : : Parser module is ideal in situations where
you need to extract or convert those elements into anotherform . Converting an
XML document into an HTML format for display on screen is a good example. We”re
going to be looking at a CGI script that I wrote on behalf of a client who wanted
tto convert an XML document into HTML for displaying on its Web site. The documents
themselves were a mixture of XML and some HTML components, and you can see a sample
in Listing 14.2 Listing
14.2: A Sample Review Document
<video>
<main>
<title>Alien
Resurrection</title>
<para>Sigourney Weaver, Winona Ryder</para>
<title>Witness
the Resurrection</title>
<para>The review..</para>
</main>
<panel>
_______________________________________________
_______________________________________________
FREE
Subscription
Subscribe to our mailing list and receive new articles
through email. Keep yourself updated with latest
developments in the industry.
Note
: We never rent, trade, or sell my email lists to
anyone.
We assure that your privacy is respected
and protected.
_______________________________________
Recommended
XML Books
| |