XML::LibXML::Simple - XML::LibXML clone of XML::Simple::XMLin

NAME

XML::LibXML::Simple - XML::LibXML clone of XML::Simple::XMLin()

INHERITANCE

 XML::LibXML::Simple
   is a Exporter

SYNOPSIS

  my $xml  = ...;  # filename, fh, string, or XML::LibXML-node

Imperative:

  use XML::LibXML::Simple   qw(XMLin);
  my $data = XMLin $xml, %options;

Or the Object Oriented way:

  use XML::LibXML::Simple   ();
  my $xs   = XML::LibXML::Simple->new(%options);
  my $data = $xs->XMLin($xml, %options);

DESCRIPTION

This module is a blunt rewrite of XML::Simple (by Grant McLean) to use the XML::LibXML parser for XML structures, where the original uses plain Perl or SAX parsers.

METHODS

Constructors

XML::LibXML::Simple->new(%options)
Instantiate an object, which can be used to call XMLin() on. You can provide %options to this constructor (to be reused for each call to XMLin) and with each call of XMLin (to be used once)

For descriptions of the %options see the DETAILS section of this manual page.

Translators

$obj->XMLin($xmldata, %options)
For $xmldata and descriptions of the %options see the DETAILS section of this manual page.

FUNCTIONS

The functions XMLin (exported implictly) and xml_in (exported on request) simply call <XML::LibXML::Simple-new->XMLin() >> with the provided parameters.

DETAILS

Parameter $xmldata

As first parameter to XMLin() must provide the XML message to be translated into a Perl structure. Choose one of the following:

A filename
If the filename contains no directory components, XMLin() will look for the file in each directory in the SearchPath (see OPTIONS below) and in the current directory. eg: 
  $data = XMLin('/etc/params.xml', %options);

Note, the filename - (dash) can be used to parse from STDIN.

undef
If there is no XML specifier, XMLin() will check the script directory and each of the SearchPath directories for a file with the same name as the script but with the extension '.xml'. Note: if you wish to specify options, you must specify the value 'undef'. eg: 
  $data = XMLin(undef, ForceArray => 1);

A string of XML
A string containing XML (recognised by the presence of '<' and '>' characters) will be parsed directly. eg: 
  $data = XMLin('<opt username="bob" password="flurp" />', %options);

An IO::Handle object
In this case, XML::LibXML::Parser will read the XML data directly from the provided file. 
  $fh  = IO::File->new('/etc/params.xml');
  $data = XMLin($fh, %options);

An XML::LibXML::Document or ::Element
[Not available in XML::Simple] When you have a pre-parsed XML::LibXML node, you can pass that.

Parameter %options

XML::LibXML::Simple supports most options defined by XML::Simple, so the interface is quite compatible. Minor changes apply. This explanation is extracted from the XML::Simple manual-page.

In alphabetic order:

ContentKey => 'keyname' # seldom used
When text content is parsed to a hash value, this option let's you specify a name for the hash key to override the default 'content'. So for example: 
  XMLin('<opt one="1">Two</opt>', ContentKey => 'text')

will parse to:

  { one => 1, text => 'Two' }

instead of:

  { one => 1, content => 'Two' }

You can also prefix your selected key name with a '-' character to have XMLin() try a little harder to eliminate unnecessary 'content' keys after array folding. For example:

  XMLin(
    '<opt><item name="one">First</item><item name="two">Second</item></opt>', 
    KeyAttr => {item => 'name'}, 
    ForceArray => [ 'item' ],
    ContentKey => '-content'
  )

will parse to:

  {
     item => {
      one =>  'First'
      two =>  'Second'
    }
  }

rather than this (without the '-'):

  {
    item => {
      one => { content => 'First' }
      two => { content => 'Second' }
    }
  }

ForceArray => 1 # important
This option should be set to '1' to force nested elements to be represented as arrays even when there is only one. Eg, with ForceArray enabled, this XML: 
    <opt>
      <name>value</name>
    </opt>

would parse to this:

    { name => [ 'value' ] }

instead of this (the default):

    { name => 'value' }

This option is especially useful if the data structure is likely to be written back out as XML and the default behaviour of rolling single nested elements up into attributes is not desirable.

If you are using the array folding feature, you should almost certainly enable this option. If you do not, single nested elements will not be parsed to arrays and therefore will not be candidates for folding to a hash. (Given that the default value of 'KeyAttr' enables array folding, the default value of this option should probably also have been enabled as well).

ForceArray => [ names ] # important
This alternative (and preferred) form of the 'ForceArray' option allows you to specify a list of element names which should always be forced into an array representation, rather than the 'all or nothing' approach above.

It is also possible to include compiled regular expressions in the list --any element names which match the pattern will be forced to arrays. If the list contains only a single regex, then it is not necessary to enclose it in an arrayref. Eg:

  ForceArray => qr/_list$/

ForceContent => 1 # seldom used
When XMLin() parses elements which have text content as well as attributes, the text content must be represented as a hash value rather than a simple scalar. This option allows you to force text content to always parse to a hash value even when there are no attributes. So for example: 
  XMLin('<opt><x>text1</x><y a="2">text2</y></opt>', ForceContent => 1)

will parse to:

  {
    x => {         content => 'text1' },
    y => { a => 2, content => 'text2' }
  }

instead of:

  {
    x => 'text1',
    y => { 'a' => 2, 'content' => 'text2' }
  }

GroupTags => { grouping tag => grouped tag } # handy
You can use this option to eliminate extra levels of indirection in your Perl data structure. For example this XML: 
  <opt>
   <searchpath>
     <dir>/usr/bin</dir>
     <dir>/usr/local/bin</dir>
     <dir>/usr/X11/bin</dir>
   </searchpath>
 </opt>

Would normally be read into a structure like this:

  {
    searchpath => {
       dir => [ '/usr/bin', '/usr/local/bin', '/usr/X11/bin' ]
    }
  }

But when read in with the appropriate value for 'GroupTags':

  my $opt = XMLin($xml, GroupTags => { searchpath => 'dir' });

It will return this simpler structure:

  {
    searchpath => [ '/usr/bin', '/usr/local/bin', '/usr/X11/bin' ]
  }

The grouping element (<searchpath> in the example) must not contain any attributes or elements other than the grouped element.

You can specify multiple 'grouping element' to 'grouped element' mappings in the same hashref. If this option is combined with KeyAttr, the array folding will occur first and then the grouped element names will be eliminated.

KeepRoot => 1 # handy
In its attempt to return a data structure free of superfluous detail and unnecessary levels of indirection, XMLin() normally discards the root element name. Setting the 'KeepRoot' option to '1' will cause the root element name to be retained. So after executing this code: 
  $config = XMLin('<config tempdir="/tmp" />', KeepRoot => 1)

You'll be able to reference the tempdir as $config->{config}->{tempdir} instead of the default $config->{tempdir}.

KeyAttr => [ list ] # important
This option controls the 'array folding' feature which translates nested elements from an array to a hash. It also controls the 'unfolding' of hashes to arrays.

For example, this XML:

    <opt>
      <user login="grep" fullname="Gary R Epstein" />
      <user login="stty" fullname="Simon T Tyson" />
    </opt>

would, by default, parse to this:

    {
      user => [
         { login    => 'grep',
           fullname => 'Gary R Epstein'
         },
         { login    => 'stty',
           fullname => 'Simon T Tyson'
         }
      ]
    }

If the option 'KeyAttr => ``login''' were used to specify that the 'login' attribute is a key, the same XML would parse to:

    {
      user => {
         stty => { fullname => 'Simon T Tyson' },
         grep => { fullname => 'Gary R Epstein' }
      }
    }

The key attribute names should be supplied in an arrayref if there is more than one. XMLin() will attempt to match attribute names in the order supplied.

Note 1: The default value for 'KeyAttr' is ['name', 'key', 'id']. If you do not want folding on input or unfolding on output you must setting this option to an empty list to disable the feature.

Note 2: If you wish to use this option, you should also enable the ForceArray option. Without 'ForceArray', a single nested element will be rolled up into a scalar rather than an array and therefore will not be folded (since only arrays get folded).

KeyAttr => { list } # important
This alternative (and preferred) method of specifiying the key attributes allows more fine grained control over which elements are folded and on which attributes. For example the option 'KeyAttr => { package => 'id' } will cause any package elements to be folded on the 'id' attribute. No other elements which have an 'id' attribute will be folded at all.

Two further variations are made possible by prefixing a '+' or a '-' character to the attribute name:

The option 'KeyAttr => { user => ``+login'' }' will cause this XML:

    <opt>
      <user login="grep" fullname="Gary R Epstein" />
      <user login="stty" fullname="Simon T Tyson" />
    </opt>

to parse to this data structure:

    {
      user => {
         stty => {
            fullname => 'Simon T Tyson',
            login    => 'stty'
         },
         grep => {
            fullname => 'Gary R Epstein',
            login    => 'grep'
         }
      }
    }

The '+' indicates that the value of the key attribute should be copied rather than moved to the folded hash key.

A '-' prefix would produce this result:

    {
      user => {
         stty => {
            fullname => 'Simon T Tyson',
            -login   => 'stty'
         },
         grep => {
            fullname => 'Gary R Epstein',
            -login    => 'grep'
         }
      }
    }

NoAttr => 1 # handy
When used with XMLin(), any attributes in the XML will be ignored.

NormaliseSpace => 0 | 1 | 2 # handy
This option controls how whitespace in text content is handled. Recognised values for the option are:
``0''
(default) whitespace is passed through unaltered (except of course for the normalisation of whitespace in attribute values which is mandated by the XML recommendation)

``1''
whitespace is normalised in any value used as a hash key (normalising means removing leading and trailing whitespace and collapsing sequences of whitespace characters to a single space)

``2''
whitespace is normalised in all text content

Note: you can spell this option with a 'z' if that is more natural for you.

Parser => OBJECT
You may pass your own XML::LibXML object, in stead of having one created for you. This is useful when you need specific configuration on that object (See XML::LibXML::Parser) or have implemented your own extension to that object.

The internally created parser object is configured in safe mode. Read the XML::LibXML::Parser manual about security issues with certain parameter settings. The default is unsafe!

ParserOpts => HASH|ARRAY
Pass parameters to the creation of a new internal parser object. You can overrule the options which will create a safe parser. It may be more readible to use the Parser parameter.

SearchPath => [ list ] # handy
If you pass XMLin() a filename, but the filename include no directory component, you can use this option to specify which directories should be searched to locate the file. You might use this option to search first in the user's home directory, then in a global directory such as /etc.

If a filename is provided to XMLin() but SearchPath is not defined, the file is assumed to be in the current directory.

If the first parameter to XMLin() is undefined, the default SearchPath will contain only the directory in which the script itself is located. Otherwise the default SearchPath will be empty.

ValueAttr => [ names ] # handy
Use this option to deal elements which always have a single attribute and no content. Eg: 
  <opt>
    <colour value="red" />
    <size   value="XXL" />
  </opt>

Setting ValueAttr => [ 'value' ] will cause the above XML to parse to:

  {
    colour => 'red',
    size   => 'XXL'
  }

instead of this (the default):

  {
    colour => { value => 'red' },
    size   => { value => 'XXL' }
  }

NsExpand => 0 advised
When name-spaces are used, the default behavior is to include the prefix in the key name. However, this is very dangerous: the prefixes can be changed without a change of the XML message meaning. Therefore, you can better use this NsExpand option. The downside, however, is that the labels get very long.

Without this option:

  <record xmlns:x="http://xyz">
    <x:field1>42</x:field1>
  </record>
  <record xmlns:y="http://xyz">
    <y:field1>42</y:field1>
  </record>

translates into

  { 'x:field1' => 42 }
  { 'y:field1' => 42 }

but both source component have exactly the same meaning. When NsExpand is used, the result is:

  { '{http://xyz}field1' => 42 }
  { '{http://xyz}field1' => 42 }

Of course, addressing these fields is more work. It is advised to implement it like this:

  my $ns = 'http://xyz';
  $data->{"{$ns}field1"};

NsStrip => 0 sloppy coding
[not available in XML::Simple] Namespaces are really important to avoid name collissions, but they are a bit of a hassle. To do it correctly, use option NsExpand. To do it sloppy, use NsStrip. With this option set, the above example will return 
  { field1 => 42 }
  { field1 => 42 }

EXAMPLES

When XMLin() reads the following very simple piece of XML:

    <opt username="testuser" password="frodo"></opt>

it returns the following data structure:

    {
      username => 'testuser',
      password => 'frodo'
    }

The identical result could have been produced with this alternative XML:

    <opt username="testuser" password="frodo" />

Or this (although see 'ForceArray' option for variations):

    <opt>
      <username>testuser</username>
      <password>frodo</password>
    </opt>

Repeated nested elements are represented as anonymous arrays:

    <opt>
      <person firstname="Joe" lastname="Smith">
        <email>joe@smith.com</email>
        <email>jsmith@yahoo.com</email>
      </person>
      <person firstname="Bob" lastname="Smith">
        <email>bob@smith.com</email>
      </person>
    </opt>
    {
      person => [
        { email     => [ 'joe@smith.com', 'jsmith@yahoo.com' ],
          firstname => 'Joe',
          lastname  => 'Smith'
        },
        { email     => 'bob@smith.com',
          firstname => 'Bob',
          lastname  => 'Smith'
        }
      ]
    }

Nested elements with a recognised key attribute are transformed (folded) from an array into a hash keyed on the value of that attribute (see the KeyAttr option):

    <opt>
      <person key="jsmith" firstname="Joe" lastname="Smith" />
      <person key="tsmith" firstname="Tom" lastname="Smith" />
      <person key="jbloggs" firstname="Joe" lastname="Bloggs" />
    </opt>
    {
      person => {
         jbloggs => {
            firstname => 'Joe',
            lastname  => 'Bloggs'
         },
         tsmith  => {
            firstname => 'Tom',
            lastname  => 'Smith'
         },
         jsmith => {
            firstname => 'Joe',
            lastname => 'Smith'
         }
      }
    }

The <anon> tag can be used to form anonymous arrays:

    <opt>
      <head><anon>Col 1</anon><anon>Col 2</anon><anon>Col 3</anon></head>
      <data><anon>R1C1</anon><anon>R1C2</anon><anon>R1C3</anon></data>
      <data><anon>R2C1</anon><anon>R2C2</anon><anon>R2C3</anon></data>
      <data><anon>R3C1</anon><anon>R3C2</anon><anon>R3C3</anon></data>
    </opt>
    {
      head => [ [ 'Col 1', 'Col 2', 'Col 3' ] ],
      data => [ [ 'R1C1', 'R1C2', 'R1C3' ],
                [ 'R2C1', 'R2C2', 'R2C3' ],
                [ 'R3C1', 'R3C2', 'R3C3' ]
              ]
    }

Anonymous arrays can be nested to arbirtrary levels and as a special case, if the surrounding tags for an XML document contain only an anonymous array the arrayref will be returned directly rather than the usual hashref:

    <opt>
      <anon><anon>Col 1</anon><anon>Col 2</anon></anon>
      <anon><anon>R1C1</anon><anon>R1C2</anon></anon>
      <anon><anon>R2C1</anon><anon>R2C2</anon></anon>
    </opt>
    [
      [ 'Col 1', 'Col 2' ],
      [ 'R1C1', 'R1C2' ],
      [ 'R2C1', 'R2C2' ]
    ]

Elements which only contain text content will simply be represented as a scalar. Where an element has both attributes and text content, the element will be represented as a hashref with the text content in the 'content' key (see the ContentKey option):

  <opt>
    <one>first</one>
    <two attr="value">second</two>
  </opt>
  {
    one => 'first',
    two => { attr => 'value', content => 'second' }
  }

Mixed content (elements which contain both text content and nested elements) will be not be represented in a useful way - element order and significant whitespace will be lost. If you need to work with mixed content, then XML::Simple is not the right tool for your job - check out the next section.

Differences to XML::Simple

In general, the output and the options are equivalent, although this module has some differences with XML::Simple to be aware of.

only XMLin() is supported
If you want to write XML then use a schema (for instance with XML::Compile). Do not attempt to create XML by hand! If you still think you need it, then have a look at XMLout() as implemented by XML::Simple or any of a zillion template systems.

no ``variables'' option
IMO, you should use a templating system if you want variables filled-in in the input: it is not a task for this module.

empty elements are not removed
Being empty has a meaning which should not be ignored.

ForceArray options
There are a few small differences in the result of the forcearray option, because XML::Simple seems to behave inconsequently.

SEE ALSO

the XML::Compile manpage for processing XML when a schema is available. When you have a schema, the data and structure of your message get validated.

the XML::Simple manpage, the original implementation which interface is followed as closely as possible.

COPYRIGHTS

The interface design and large parts of the documentation were taken from the the XML::Simple manpage module, written by Grant McLean <grantm@cpan.org>

Copyrights of the perl code and the related documentation by 2008-2014 by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See http://www.perl.com/perl/misc/Artistic.html

 XML::LibXML::Simple - XML::LibXML clone of XML::Simple::XMLin