NAME¶
XML::LibXML::Simple - XML::LibXML clone of XML::Simple::XMLin()
INHERITANCE¶
XML::LibXML::Simple
is a Exporter
SYNOPSIS¶
use XML::LibXML::Simple qw(XMLin);
my $xml = XMLin <xml file or string>, OPTIONS;
Or the Object Oriented way:
use XML::LibXML::Simple ();
my $xs = XML::LibXML::Simple->new(OPTIONS);
my $ref = $xs->XMLin(<xml file or string>, 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¶
Differences with 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.
Parameter XML-DATA¶
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:
$ref = XMLin('/etc/params.xml');
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:
$ref = XMLin(undef, ForceArray => 1);
- A string of XML
- A string containing XML (recognised by the presence of '<' and '>'
characters) will be parsed directly. eg:
$ref = XMLin('<opt username="bob" password="flurp" />');
- An IO::Handle object
- An IO::Handle object will be read to EOF and its contents parsed. eg:
$fh = IO::File->new('/etc/params.xml');
$ref = XMLin($fh);
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.
- •
- check out "ForceArray" because you'll almost certainly want to
turn it on
- •
- make sure you know what the "KeyAttr" option does and what its
default value is because it may surprise you otherwise.
- •
- Option names are case in-sensitive so you can use the mixed case versions
shown here; you can add underscores between the words (eg: key_attr) if
you like.
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.
SEE ALSO¶
XML::Compile for processing XML when a schema is available
XML::Simple, the SAX and original implementation
COPYRIGHTS¶
The interface design and large parts of the documentation were taken from the
XML::Simple 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