XML::Generator man page on OpenServer
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Generator(3) User Contributed Perl Documentation Generator(3)
NAME
XML::Generator - Perl extension for generating XML
SYNOPSIS
use XML::Generator ':pretty';
print foo(bar({ baz => 3 }, bam()),
bar([ 'qux' => 'http://qux.com/' ],
"Hey there, world"));
# OR
require XML::Generator;
my $X = XML::Generator->new(':pretty');
print $X->foo($X->bar({ baz => 3 }, $X->bam()),
$X->bar([ 'qux' => 'http://qux.com/' ],
"Hey there, world"));
Either of the above yield:
<foo xmlns:qux="http://qux.com/">
<bar baz="3">
<bam />
</bar>
<qux:bar>Hey there, world</qux:bar>
</foo>
DESCRIPTION
In general, once you have an XML::Generator object, you then simply
call methods on that object named for each XML tag you wish to gener-
ate.
XML::Generator can also arrange for undefined subroutines in the
caller's package to generate the corresponding XML, by exporting an
"AUTOLOAD" subroutine to your package. Just supply an ':import' argu-
ment to your "use XML::Generator;" call. If you already have an
"AUTOLOAD" defined then XML::Generator can be configured to cooperate
with it. See "STACKABLE AUTOLOADs".
Say you want to generate this XML:
<person>
<name>Bob</name>
<age>34</age>
<job>Accountant</job>
</person>
Here's a snippet of code that does the job, complete with pretty print-
ing:
use XML::Generator;
my $gen = XML::Generator->new(':pretty');
print $gen->person(
$gen->name("Bob"),
$gen->age(34),
$gen->job("Accountant")
);
The only problem with this is if you want to use a tag name that Perl's
lexer won't understand as a method name, such as "shoe-size". Fortu-
nately, since you can store the name of a method in a variable, there's
a simple work-around:
my $shoe_size = "shoe-size";
$xml = $gen->$shoe_size("12 1/2");
Which correctly generates:
<shoe-size>12 1/2</shoe-size>
You can use a hash ref as the first parameter if the tag should include
atributes. Normally this means that the order of the attributes will
be unpredictable, but if you have the Tie::IxHash module, you can use
it to get the order you want, like this:
use Tie::IxHash;
tie my %attr, 'Tie::IxHash';
%attr = (name => 'Bob',
age => 34,
job => 'Accountant',
'shoe-size' => '12 1/2');
print $gen->person(\%attr);
This produces
<person name="Bob" age="34" job="Accountant" shoe-size="12 1/2" />
An array ref can also be supplied as the first argument to indicate a
namespace for the element and the attributes.
If there is one element in the array, it is considered the URI of the
default namespace, and the tag will have an xmlns="URI" attribute added
automatically. If there are two elements, the first should be the tag
prefix to use for the namespace and the second element should be the
URI. In this case, the prefix will be used for the tag and an
xmlns:PREFIX attribute will be automatically added. Prior to version
0.99, this prefix was also automatically added to each attribute name.
Now, the default behavior is to leave the attributes alone (although
you may always explicitly add a prefix to an attribute name). If the
prior behavior is desired, use the constructor option "quali-
fied_attributes".
If you specify more than two elements, then each pair should correspond
to a tag prefix and the corresponding URL. An xmlns:PREFIX attribute
will be added for each pair, and the prefix from the first such pair
will be used as the tag's namespace. If you wish to specify a default
namespace, use '#default' for the prefix. If the default namespace is
first, then the tag will use the default namespace itself.
If you want to specify a namespace as well as attributes, you can make
the second argument a hash ref. If you do it the other way around, the
array ref will simply get stringified and included as part of the con-
tent of the tag.
Here's an example to show how the attribute and namespace parameters
work:
$xml = $gen->account(
$gen->open(['transaction'], 2000),
$gen->deposit(['transaction'], { date => '1999.04.03'}, 1500)
);
This generates:
<account>
<open xmlns="transaction">2000</open>
<deposit xmlns="transaction" date="1999.04.03">1500</deposit>
</account>
Because default namespaces inherit, XML::Generator takes care to output
the xmlns="URI" attribute as few times as strictly necessary. For
example,
$xml = $gen->account(
$gen->open(['transaction'], 2000),
$gen->deposit(['transaction'], { date => '1999.04.03'},
$gen->amount(['transaction'], 1500)
)
);
This generates:
<account>
<open xmlns="transaction">2000</open>
<deposit xmlns="transaction" date="1999.04.03">
<amount>1500</amount>
</deposit>
</account>
Notice how "xmlns="transaction"" was left out of the "<amount"> tag.
Here is an example that uses the two-argument form of the namespace:
$xml = $gen->widget(['wru' => 'http://www.widgets-r-us.com/xml/'],
{'id' => 123}, $gen->contents());
<wru:widget xmlns:wru="http://www.widgets-r-us.com/xml/" id="123">
<contents />
</wru:widget>
Here is an example that uses multiple namespaces. It generates the
first example from the RDF primer (<http://www.w3.org/TR/rdf-primer/>).
my $contactNS = [contact => "http://www.w3.org/2000/10/swap/pim/contact#"];
$xml = $gen->xml(
$gen->RDF([ rdf => "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
@$contactNS ],
$gen->Person($contactNS, { 'rdf:about' => "http://www.w3.org/People/EM/contact#me" },
$gen->fullName($contactNS, 'Eric Miller'),
$gen->mailbox($contactNS, {'rdf:resource' => "mailto:em@w3.org"}),
$gen->personalTitle($contactNS, 'Dr.'))));
<?xml version="1.0" standalone="yes"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:contact="http://www.w3.org/2000/10/swap/pim/contact#">
<contact:Person rdf:about="http://www.w3.org/People/EM/contact#me">
<contact:fullName>Eric Miller</contact:fullName>
<contact:mailbox rdf:resource="mailto:em@w3.org" />
<contact:personalTitle>Dr.</contact:personalTitle>
</Person>
</rdf:RDF>
CONSTRUCTOR
XML::Generator->new(':option', ...);
XML::Generator->new(option => 'value', ...);
(Both styles may be combined)
The following options are available:
:std, :standard
Equivalent to
escape => 'always',
conformance => 'strict',
:strict
Equivalent to
conformance => 'strict',
:pretty[=N]
Equivalent to
escape => 'always',
conformance => 'strict',
pretty => N # N defaults to 2
namespace
This value of this option must be an array reference containing one or
two values. If the array contains one value, it should be a URI and
will be the value of an 'xmlns' attribute in the top-level tag. If
there are two or more elements, the first of each pair should be the
namespace tag prefix and the second the URI of the namespace. This
will enable behavior similar to the namespace behavior in previous ver-
sions; the tag prefix will be applied to each tag. In addition, an
xmlns:NAME="URI" attribute will be added to the top-level tag. Prior
to version 0.99, the tag prefix was also automatically added to each
attribute name, unless overridden with an explicit prefix. Now, the
attribute names are left alone, but if the prior behavior is desired,
use the constructor option "qualified_attributes".
The value of this option is used as the global default namespace. For
example,
my $html = XML::Generator->new(
pretty => 2,
namespace => [HTML => "http://www.w3.org/TR/REC-html40"]);
print $html->html(
$html->body(
$html->font({ face => 'Arial' },
"Hello, there")));
would yield
<HTML:html xmlns:HTML="http://www.w3.org/TR/REC-html40">
<HTML:body>
<HTML:font face="Arial">Hello, there</HTML:font>
</HTML:body>
</HTML:html>
Here is the same example except without all the prefixes:
my $html = XML::Generator->new(
pretty => 2,
namespace => ["http://www.w3.org/TR/REC-html40"]);
print $html->html(
$html->body(
$html->font({ 'face' => 'Arial' },
"Hello, there")));
would yield
<html xmlns="http://www.w3.org/TR/REC-html40">
<body>
<font face="Arial">Hello, there</font>
</body>
</html>
qualifiedAttributes, qualified_attributes
Set this to a true value to emulate the attribute prefixing behavior of
XML::Generator prior to version 0.99. Here is an example:
my $foo = XML::Generator->new(
namespace => [foo => "http://foo.com/"],
qualifiedAttributes => 1);
print $foo->bar({baz => 3});
yields
<foo:bar xmlns:foo="http://foo.com/" foo:baz="3" />
escape
The contents and the values of each attribute have any illegal XML
characters escaped if this option is supplied. If the value is
'always', then &, < and > (and " within attribute values) will be con-
verted into the corresponding XML entity, although & will not be con-
verted if it looks like it could be part of a valid entity (but see
below). If the value is 'unescaped', then the escaping will be turned
off character-by- character if the character in question is preceded by
a backslash, or for the entire string if it is supplied as a scalar
reference. So, for example,
use XML::Generator escape => 'always';
one('<'); # <one><</one>
two('\&'); # <two>\&</two>
three(\'>'); # <three>></three> (scalar refs always allowed)
four('<'); # <four><</four> (looks like an entity)
five('"'); # <five>"</five> (looks like an entity)
but
use XML::Generator escape => 'unescaped';
one('<'); # <one><</one>
two('\&'); # <two>&</two>
three(\'>'); # <three>></three> (aiee!)
four('<'); # <four><</four> (no special case for entities)
By default, high-bit data will be passed through unmodified, so that
UTF-8 data can be generated with pre-Unicode perls. If you know that
your data is ASCII, use the value 'high-bit' for the escape option and
bytes with the high bit set will be turned into numeric entities. You
can combine this functionality with the other escape options by comma-
separating the values:
my $a = XML::Generator->new(escape => 'always,high-bit');
print $a->foo("<\242>");
yields
<foo><¢></foo>
Because XML::Generator always uses double quotes ("") around attribute
values, it does not escape single quotes. If you want single quotes
inside attribute values to be escaped, use the value 'apos' along with
'always' or 'unescaped' for the escape option. For example:
my $gen = XML::Generator->new(escape => 'always,apos');
print $gen->foo({'bar' => "It's all good"});
<foo bar="It's all good" />
If you actually want & to be converted to & even if it looks like
it could be part of a valid entity, use the value 'even-entities' along
with 'always'. Supplying 'even-entities' to the 'unescaped' option is
meaningless as entities are already escaped with that option.
pretty
To have nice pretty printing of the output XML (great for config files
that you might also want to edit by hand), supply an integer for the
number of spaces per level of indenting, eg.
my $gen = XML::Generator->new(pretty => 2);
print $gen->foo($gen->bar('baz'),
$gen->qux({ tricky => 'no'}, 'quux'));
would yield
<foo>
<bar>baz</bar>
<qux tricky="no">quux</qux>
</foo>
You may also supply a non-numeric string as the argument to 'pretty',
in which case the indents will consist of repetitions of that string.
So if you want tabbed indents, you would use:
my $gen = XML::Generator->new(pretty => "\t");
Pretty printing does not apply to CDATA sections or Processing Instruc-
tions.
conformance
If the value of this option is 'strict', a number of syntactic checks
are performed to ensure that generated XML conforms to the formal XML
specification. In addition, since entity names beginning with 'xml'
are reserved by the W3C, inclusion of this option enables several spe-
cial tag names: xmlpi, xmlcmnt, xmldecl, xmldtd, xmlcdata, and xml to
allow generation of processing instructions, comments, XML declara-
tions, DTD's, character data sections and "final" XML documents,
respectively.
See "XML CONFORMANCE" and "SPECIAL TAGS" for more information.
allowedXMLTags, allowed_xml_tags
If you have specified 'conformance' => 'strict' but need to use tags
that start with 'xml', you can supply a reference to an array contain-
ing those tags and they will be accepted without error. It is not an
error to supply this option if 'conformance' => 'strict' is not sup-
plied, but it will have no effect.
empty
There are 5 possible values for this option:
self - create empty tags as <tag /> (default)
compact - create empty tags as <tag/>
close - close empty tags as <tag></tag>
ignore - don't do anything (non-compliant!)
args - use count of arguments to decide between <x /> and <x></x>
Many web browsers like the 'self' form, but any one of the forms
besides 'ignore' is acceptable under the XML standard.
'ignore' is intended for subclasses that deal with HTML and other SGML
subsets which allow atomic tags. It is an error to specify both 'con-
formance' => 'strict' and 'empty' => 'ignore'.
'args' will produce <x /> if there are no arguments at all, or if there
is just a single undef argument, and <x></x> otherwise.
version
Sets the default XML version for use in XML declarations. See
"xmldecl" below.
encoding
Sets the default encoding for use in XML declarations.
dtd
Specify the dtd. The value should be an array reference with three
values; the type, the name and the uri.
IMPORT ARGUMENTS
use XML::Generator ':option';
use XML::Generator option => 'value';
(Both styles may be combined)
:import
Cause "use XML::Generator;" to export an "AUTOLOAD" to your package
that makes undefined subroutines generate XML tags corresponding to
their name. Note that if you already have an "AUTOLOAD" defined, it
will be overwritten.
:stacked
Implies :import, but if there is already an "AUTOLOAD" defined, the
overriding "AUTOLOAD" will still give it a chance to run. See "STACKED
AUTOLOADs".
ANYTHING ELSE
If you supply any other options, :import is implied and the XML::Gener-
ator object that is created to generate tags will be constructed with
those options.
XML CONFORMANCE
When the 'conformance' => 'strict' option is supplied, a number of syn-
tactic checks are enabled. All entity and attribute names are checked
to conform to the XML specification, which states that they must begin
with either an alphabetic character or an underscore and may then con-
sist of any number of alphanumerics, underscores, periods or hyphens.
Alphabetic and alphanumeric are interpreted according to the current
locale if 'use locale' is in effect and according to the Unicode stan-
dard for Perl versions >= 5.6. Furthermore, entity or attribute names
are not allowed to begin with 'xml' (in any case), although a number of
special tags beginning with 'xml' are allowed (see "SPECIAL TAGS").
Note that you can also supply an explicit list of allowed tags with the
'allowed_xml_tags' option.
SPECIAL TAGS
The following special tags are available when running under strict con-
formance (otherwise they don't act special):
xmlpi
Processing instruction; first argument is target, remaining arguments
are attribute, value pairs. Attribute names are syntax checked, values
are escaped.
xmlcmnt
Comment. Arguments are concatenated and placed inside <!-- ... -->
comment delimiters. Any occurences of '--' in the concatenated argu-
ments are converted to '--'
xmldecl(@args)
Declaration. This can be used to specify the version, encoding, and
other XML-related declarations (i.e., anything inside the <?xml?> tag).
@args can be used to control what is output, as keyword-value pairs.
By default, the version is set to the value specified in the construc-
tor, or to 1.0 if it was not specified. This can be overridden by pro-
viding a 'version' key in @args. If you do not want the version at
all, explicitly provide undef as the value in @args.
By default, the encoding is set to the value specified in the construc-
tor; if no value was specified, the encoding will be left out alto-
gether. Provide an 'encoding' key in @args to override this.
If a dtd was set in the constructor, the standalone attribute of the
declaration will be set to 'no' and the doctype declaration will be
appended to the XML declartion, otherwise the standalone attribute will
be set to 'yes'. This can be overridden by providing a 'standalone'
key in @args. If you do not want the standalone attribute to show up,
explicitly provide undef as the value.
xmldtd
DTD <!DOCTYPE> tag creation. The format of this method is different
from others. Since DTD's are global and cannot contain namespace infor-
mation, the first argument should be a reference to an array; the ele-
ments are concatenated together to form the DTD:
print $xml->xmldtd([ 'html', 'PUBLIC', $xhtml_w3c, $xhtml_dtd ])
This would produce the following declaration:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"DTD/xhtml1-transitional.dtd">
Assuming that $xhtml_w3c and $xhtml_dtd had the correct values.
Note that you can also specify a DTD on creation using the new()
method's dtd option.
xmlcdata
Character data section; arguments are concatenated and placed inside
<![CDATA[ ... ]]> character data section delimiters. Any occurences of
']]>' in the concatenated arguments are converted to ']]>'.
xml
"Final" XML document. Must be called with one and exactly one
XML::Generator-produced XML document. Any combination of XML::Genera-
tor-produced XML comments or processing instructions may also be sup-
plied as arguments. Prepends an XML declaration, and re-blesses the
argument into a "final" class that can't be embedded.
CREATING A SUBCLASS
For a simpler way to implement subclass-like behavior, see "STACKABLE
AUTOLOADs".
At times, you may find it desireable to subclass XML::Generator. For
example, you might want to provide a more application-specific inter-
face to the XML generation routines provided. Perhaps you have a custom
database application and would really like to say:
my $dbxml = new XML::Generator::MyDatabaseApp;
print $dbxml->xml($dbxml->custom_tag_handler(@data));
Here, custom_tag_handler() may be a method that builds a recursive XML
structure based on the contents of @data. In fact, it may even be named
for a tag you want generated, such as authors(), whose behavior changes
based on the contents (perhaps creating recursive definitions in the
case of multiple elements).
Creating a subclass of XML::Generator is actually relatively straight-
forward, there are just three things you have to remember:
1. All of the useful utilities are in XML::Generator::util.
2. To construct a tag you simply have to call SUPER::tagname,
where "tagname" is the name of your tag.
3. You must fully-qualify the methods in XML::Generator::util.
So, let's assume that we want to provide a custom HTML table() method:
package XML::Generator::CustomHTML;
use base 'XML::Generator';
sub table {
my $self = shift;
# parse our args to get namespace and attribute info
my($namespace, $attr, @content) =
$self->XML::Generator::util::parse_args(@_)
# check for strict conformance
if ( $self->XML::Generator::util::config('conformance') eq 'strict' ) {
# ... special checks ...
}
# ... special formatting magic happens ...
# construct our custom tags
return $self->SUPER::table($attr, $self->tr($self->td(@content)));
}
That's pretty much all there is to it. We have to explicitly call
SUPER::table() since we're inside the class's table() method. The oth-
ers can simply be called directly, assuming that we don't have a tr()
in the current package.
If you want to explicitly create a specific tag by name, or just want a
faster approach than AUTOLOAD provides, you can use the tag() method
directly. So, we could replace that last line above with:
# construct our custom tags
return $self->XML::Generator::util::tag('table', $attr, ...);
Here, we must explicitly call tag() with the tag name itself as its
first argument so it knows what to generate. These are the methods that
you might find useful:
XML::Generator::util::parse_args()
This parses the argument list and returns the namespace (arrayref),
attributes (hashref), and remaining content (array), in that order.
XML::Generator::util::tag()
This does the work of generating the appropriate tag. The first
argument must be the name of the tag to generate.
XML::Generator::util::config()
This retrieves options as set via the new() method.
XML::Generator::util::escape()
This escapes any illegal XML characters.
Remember that all of these methods must be fully-qualified with the
XML::Generator::util package name. This is because AUTOLOAD is used by
the main XML::Generator package to create tags. Simply calling
parse_args() will result in a set of XML tags called <parse_args>.
Finally, remember that since you are subclassing XML::Generator, you do
not need to provide your own new() method. The one from XML::Generator
is designed to allow you to properly subclass it.
STACKABLE AUTOLOADs
As a simpler alternative to traditional subclassing, the "AUTOLOAD"
that "use XML::Generator;" exports can be configured to work with a
pre-defined "AUTOLOAD" with the ':stacked' option. Simply ensure that
your "AUTOLOAD" is defined before "use XML::Generator ':stacked';" exe-
cutes. The "AUTOLOAD" will get a chance to run first; the subroutine
name will be in your $AUTOLOAD as normal. Return an empty list to let
the default XML::Generator "AUTOLOAD" run or any other value to abort
it. This value will be returned as the result of the original method
call.
If there is no "import" defined, XML::Generator will create one. All
that this "import" does is export AUTOLOAD, but that lets your package
be used as if it were a subclass of XML::Generator.
An example will help:
package MyGenerator;
my %entities = ( copy => '©',
nbsp => ' ', ... );
sub AUTOLOAD {
my($tag) = our $AUTOLOAD =~ /.*::(.*)/;
return $entities{$tag} if defined $entities{$tag};
return;
}
use XML::Generator qw(:pretty :stacked);
This lets someone do:
use MyGenerator;
print html(head(title("My Title", copy())));
Producing:
<html>
<head>
<title>My Title©</title>
</head>
</html>
AUTHORS
Benjamin Holzman <bholzman@earthlink.net>
Original author and maintainer
Bron Gondwana <perlcode@brong.net>
First modular version
Nathan Wiger <nate@nateware.com>
Modular rewrite to enable subclassing
SEE ALSO
The XML::Writer module
http://search.cpan.org/search?mode=module&query=XML::Writer
perl v5.8.8 2007-07-10 Generator(3)
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