NAME¶
XML::Dumper - Perl module for dumping Perl objects from/to XML
SYNOPSIS¶
# ===== Using an object
use XML::Dumper;
$dump = new XML::Dumper;
$xml = $dump->pl2xml( $perl );
$perl = $dump->xml2pl( $xml );
$dump->pl2xml( $perl, "my_perl_data.xml.gz" );
# ===== Using function calls
use XML::Dumper;
$xml = pl2xml( $perl );
$perl = xml2pl( $xml );
EXTENDED SYNOPSIS¶
use XML::Dumper;
my $dump = new XML::Dumper;
my $perl = '';
my $xml = '';
# ===== Convert Perl code to XML
$perl = [
{
fname => 'Fred',
lname => 'Flintstone',
residence => 'Bedrock'
},
{
fname => 'Barney',
lname => 'Rubble',
residence => 'Bedrock'
}
];
$xml = $dump->pl2xml( $perl );
# ===== Dump to a file
my $file = "dump.xml";
$dump->pl2xml( $perl, $file );
# ===== Convert XML to Perl code
$xml = q|
<perldata>
<arrayref>
<item key="0">
<hashref>
<item key="fname">Fred</item>
<item key="lname">Flintstone</item>
<item key="residence">Bedrock</item>
</hashref>
</item>
<item key="1">
<hashref>
<item key="fname">Barney</item>
<item key="lname">Rubble</item>
<item key="residence">Bedrock</item>
</hashref>
</item>
</arrayref>
</perldata>
|;
my $perl = $dump->xml2pl( $xml );
# ===== Convert an XML file to Perl code
my $perl = $dump->xml2pl( $file );
# ===== And serialize Perl code to an XML file
$dump->pl2xml( $perl, $file );
# ===== USE COMPRESSION
$dump->pl2xml( $perl, $file.".gz" );
# ===== INCLUDE AN IN-DOCUMENT DTD
$dump->dtd;
my $xml_with_dtd = $dump->pl2xml( $perl );
# ===== USE EXTERNAL DTD
$dump->dtd( $file, $url );
my $xml_with_link_to_dtd = $dump->pl2xml( $perl );
DESCRIPTION¶
XML::Dumper dumps Perl data to XML format. XML::Dumper can also read XML data
that was previously dumped by the module and convert it back to Perl. You can
use the module read the XML from a file and write the XML to a file. Perl
objects are blessed back to their original packaging; if the modules are
installed on the system where the perl objects are reconstituted from xml,
they will behave as expected. Intuitively, if the perl objects are converted
and reconstituted in the same environment, all should be well. And it is.
Additionally, because XML benefits so nicely from compression, XML::Dumper
understands gzipped XML files. It does so with an optional dependency on
Compress::Zlib. So, if you dump a Perl variable with a file that has an
extension of '.xml.gz', it will store and compress the file in gzipped format.
Likewise, if you read a file with the extension '.xml.gz', it will uncompress
the file in memory before parsing the XML back into a Perl variable.
Another fine challenge that this module rises to meet is that it understands
circular definitions and multiple references to a single object. This includes
doubly-linked lists, circular references, and the so-called 'Flyweight'
pattern of Object Oriented programming. So it can take the gnarliest of your
perl data, and should do just fine.
One caveat; XML::Dumper does not handle binary data. There have been discussions
in the expat mailing list archives discussing the challenges associated with
encoding binary data with XML. I chose the cowardly path of making the problem
a non-issue by not addressing it. To store binary data, one could encode the
data into ASCII before encapsulating the data as XML, and then reverse the
process to restore the data. There are several Perl modules that one can use
for this, Convert::UU, for example.
FUNCTIONS AND METHODS
- * new() - XML::Dumper constructor.
- Creates a lean, mean, XML dumping machine. It's also completely at your
disposal.
- * dtd -
- Generates a Document Type Dictionary for the 'perldata' data type. The
default behaviour is to embed the DTD in the XML, thereby creating valid
XML. Given a filename, the DTD will be written out to that file and the
XML document for your Perl data will link to the file. Given a filename
and an URL, the DTD will be written out the file and the XML document will
link to the URL. XML::Dumper doesn't try really hard to determine where
your DTD's ought to go or relative paths or anything, so be careful with
what arguments you supply this method, or just go with the default with
the embedded DTD. Between DTD's and Schemas, the potential for more
free-form data to be imported and exported becomes feasible.
Usage:
dtd(); # Causes XML to include embedded DTD
dtd( $file ); # DTD saved to $file; XML will link to $file
dtd( $file, $url ); # DTD saved to $file; XML will link to $url
dtd( 0 ); # Prevents XML from including embedded DTD
- * pl2xml( $xml, [ $file ] ) -
- (Also perl2xml(), for those who enjoy readability over brevity).
Converts Perl data to XML. If a second argument is given, then the Perl data
will be stored to disk as XML, using the second argument as a filename.
Usage: See Synopsis
- * xml2pl( $xml_or_filename, [ $callback ] ) -
- (Also xml2perl(), for those who enjoy readability over brevity.)
Converts XML to a Perl datatype. If this method is given a second argument,
XML::Dumper will use the second argument as a callback (if possible). If
the first argument isn't XML and exists as a file, that file will be read
and its contents will be used as the input XML.
Currently, the only supported invocation of callbacks is through soft
references. That is to say, the callback argument ought to be a string
that matches the name of a callable method for your classes. If you have a
congruent interface, this should work like a peach. If your class
interface doesn't have such a named method, it won't be called.
- * xml_compare( $xml1, $xml2 ) - Compares xml for content
- Compares two dumped Perl data structures (that is, compares the xml) for
identity in content. Use this function rather than perl's built-in string
comparison. This function will return true for any two perl data that are
either deep clones of each other, or identical. This method is exported by
default.
- * xml_identity( $xml1, $xml2 ) - Compares xml for identity
- Compares two dumped Perl data structures (that is, compares the xml) for
identity in instantiation. This function will return true for any two perl
data that are identical, but not for deep clones of each other. This
method is also exported by default.
EXPORTS¶
By default, the following methods are exported:
xml2pl, pl2xml, xml_compare, xml_identity
BUGS AND DEPENDENCIES¶
XML::Dumper has changed API since 0.4, as a response to a bug report from
PerlMonks. I felt it was necessary, as the functions simply didn't work as
advertised. That is, xml2pl really didnt accept xml as an argument; what it
wanted was an XML Parse tree. To correct for the API change, simply don't
parse the XML before feeding it to XML::Dumper.
XML::Dumper also has no understanding of typeglobs (references or not),
references to regular expressions, or references to Perl subroutines. Turns
out that Data::Dumper doesn't do references to Perl subroutines, either, so at
least I'm in somewhat good company.
XML::Dumper requires one perl module, available from CPAN
XML::Parser
XML::Parser itself relies on Clark Cooper's Expat implementation in Perl, which
in turn requires James Clark's expat package itself. See the documentation for
XML::Parser for more information.
REVISIONS AND CREDITS¶
The list of credits got so long that I had to move it to the Changes file.
Thanks to all those who've contributed with bug reports and suggested
features! Keep 'em coming!
I've had ownership of the module since June of 2002, and very much appreciate
requests on how to make the module better. It has served me well, both as a
learning tool on how I can repay my debt to the Perl Community, and as a
practical module that is useful. I'm thrilled to be able to offer this bit of
code. So, if you have suggestions, bug reports, or feature requests, please
let me know and I'll do my best to make this a better module.
CURRENT MAINTAINER¶
Mike Wong <mike_w3@pacbell.net>
XML::Dumper is free software. You can redistribute it and/or modify it under the
same terms as Perl itself.
ORIGINAL AUTHOR¶
Jonathan Eisenzopf <eisen@pobox.com>
SEE ALSO¶
perl(1) Compress::Zlib(3)
XML::Parser(3)
Data::DumpXML(3)