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);
A dash (-)
Parse from STDIN.
$data = XMLin('-', %options);
undef
[deprecated] 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);
This feature is available for backwards compatibility with XML::Simple, but quite sensitive. You can
easily hit the wrong xml file as input. Please do not use it: always use an explicit filename.
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') or die;
open my $fh, '<:encoding(utf8)', '/etc/params.xml' or die;
$data = XMLin($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.
• 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' #seldomused
When text content is parsed to a hash value, this option lets 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 #seldomused
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.
HookNodes => CODE
Select document nodes to apply special tricks. Introduced in [0.96], not available in XML::Simple.
When this option is provided, the CODE will be called once the XML DOM tree is ready to get
transformed into Perl. Your CODE should return either "undef" (nothing to do) or a HASH which maps
values of unique_key (see XML::LibXML::Node method "unique_key" onto CODE references to be called.
Once the translater from XML into Perl reaches a selected node, it will call your routine specific
for that node. That triggering node found is the only parameter. When you return "undef", the node
will not be found in the final result. You may return any data (even the node itself) which will be
included in the final result as is, under the name of the original node.
Example:
my $out = XMLin $file, HookNodes => \&protect_html;
sub protect_html($$)
{ # $obj is the instantated XML::Compile::Simple object
# $xml is a XML::LibXML::Element to get transformed
my ($obj, $xml) = @_;
my %hooks; # collects the table of hooks
# do an xpath search for HTML
my $xpc = XML::LibXML::XPathContext->new($xml);
my @nodes = $xpc->findNodes(...); #XXX
@nodes or return undef;
my $as_text = sub { $_[0]->toString(0) }; # as text
# $as_node = sub { $_[0] }; # as node
# $skip = sub { undef }; # not at all
# the same behavior for all xpath nodes, in this example
$hook{$_->unique_key} = $as_text
for @nodes;
\%hook;
}
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 specifying 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.
SuppressEmpty => 1 | '' | undef
[0.99] What to do with empty elements (no attributes and no content). The default behaviour is to
represent them as empty hashes. Setting this option to a true value (eg: 1) will cause empty
elements to be skipped altogether. Setting the option to 'undef' or the empty string will cause
empty elements to be represented as the undefined value or the empty string respectively.
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 sloppycoding
[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 }
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