Dumper(3) User Contributed Perl Documentation Dumper(3)NAMEXML::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 );
DESCRIPTIONXML::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 packag-
ing; 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 envi-
ronment, 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 exten-
sion '.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 under-
stands 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 chal-
lenges associated with encoding binary data with XML. I chose the cow-
ardly path of making the problem a non-issue by not addressing it. To
store binary data, one could encode the data into ASCII before encapsu-
lating the data as XML, and then reverse the process to restore the
data. There are several Perl modules that one can use for this, Con-
vert::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 cre-
ating 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 embed-
ded 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 identi-
cal. 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 DEPENDENCIESXML::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 argu-
ment; 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 sug-
gested 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 ALSOperl(1)Compress::Zlib(3)XML::Parser(3)Data::DumpXML(3)perl v5.8.8 2006-04-05 Dumper(3)
