NAME

XML::Dumper - Perl module for dumping Perl objects from/to XML

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 );

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 XML 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. 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.

FUNCTIONS AND METHODS

• new - XML::Dumper constructor.

  Creates a lean, mean, XML dumping machine. It's also completely at your disposal.

• pl2xml -

  (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 -

  (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. The null-string method is not supported, because I can't think of a good reason to support it. (OK, that was lame, but that kind of thinking makes my head hurt. If you can prove that null-string methods ought to be allowed, I'll do it. If you don't know what the null-string method is, curse The Damian for having invoked such a beast, and move along in blissful ignorance).

• xml_compare - 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, especially when dealing with perl data that is memory-location dependent (which pretty much means all references). 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 - 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.

BUGS AND DEPENDENCIES

XML::Dumper has changed API since 0.4. While this violates most every benefit of object-oriented programming, 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. If the whim strikes me, or if someone needs this feature, I may fix this. 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

See Changes file.

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), XML::Parser(3). Compress::Zlib(3)