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man : XML::Writer(3p)
Writer(3p) User Contributed Perl Documentation Writer(3p)
NAME
XML::Writer - Perl extension for writing XML documents.
SYNOPSIS
use XML::Writer;
use IO::File;
my $output = new IO::File(">output.xml");
my $writer = new XML::Writer(OUTPUT => $output);
$writer->startTag("greeting",
"class" => "simple");
$writer->characters("Hello, world!");
$writer->endTag("greeting");
$writer->end();
$output->close();
DESCRIPTION
XML::Writer is a helper module for Perl programs that write an XML
document. The module handles all escaping for attribute values and
character data and constructs different types of markup, such as tags,
comments, and processing instructions.
By default, the module performs several well-formedness checks to catch
errors during output. This behaviour can be extremely useful during
development and debugging, but it can be turned off for production-
grade code.
The module can operate either in regular mode in or Namespace
processing mode. In Namespace mode, the module will generate Namespace
Declarations itself, and will perform additional checks on the output.
Additional support is available for a simplified data mode with no
mixed content: newlines are automatically inserted around elements and
elements can optionally be indented based as their nesting level.
METHODS
Writing XML
new([$params])
Create a new XML::Writer object:
my $writer = new XML::Writer(OUTPUT => $output, NEWLINES => 1);
Arguments are an anonymous hash array of parameters:
OUTPUT
An object blessed into IO::Handle or one of its subclasses
(such as IO::File), or a reference to a string; if this
parameter is not present, the module will write to standard
output. If a string reference is passed, it will capture the
generated XML (as a string; to get bytes use the "Encode"
module).
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NAMESPACES
A true (1) or false (0, undef) value; if this parameter is
present and its value is true, then the module will accept two-
member array reference in the place of element and attribute
names, as in the following example:
my $rdfns = "http://www.w3.org/1999/02/22-rdf-syntax-ns#";
my $writer = new XML::Writer(NAMESPACES => 1);
$writer->startTag([$rdfns, "Description"]);
The first member of the array is a namespace URI, and the
second part is the local part of a qualified name. The module
will automatically generate appropriate namespace declarations
and will replace the URI part with a prefix.
PREFIX_MAP
A hash reference; if this parameter is present and the module
is performing namespace processing (see the NAMESPACES
parameter), then the module will use this hash to look up
preferred prefixes for namespace URIs:
my $rdfns = "http://www.w3.org/1999/02/22-rdf-syntax-ns#";
my $writer = new XML::Writer(NAMESPACES => 1,
PREFIX_MAP => {$rdfns => 'rdf'});
The keys in the hash table are namespace URIs, and the values
are the associated prefixes. If there is not a preferred
prefix for the namespace URI in this hash, then the module will
automatically generate prefixes of the form "__NS1", "__NS2",
etc.
To set the default namespace, use '' for the prefix.
FORCED_NS_DECLS
An array reference; if this parameter is present, the document
element will contain declarations for all the given namespace
URIs. Declaring namespaces in advance is particularly useful
when a large number of elements from a namespace are siblings,
but don't share a direct ancestor from the same namespace.
NEWLINES
A true or false value; if this parameter is present and its
value is true, then the module will insert an extra newline
before the closing delimiter of start, end, and empty tags to
guarantee that the document does not end up as a single, long
line. If the parameter is not present, the module will not
insert the newlines.
UNSAFE
A true or false value; if this parameter is present and its
value is true, then the module will skip most well-formedness
error checking. If the parameter is not present, the module
will perform the well-formedness error checking by default.
Turn off error checking at your own risk!
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DATA_MODE
A true or false value; if this parameter is present and its
value is true, then the module will enter a special data mode,
inserting newlines automatically around elements and (unless
UNSAFE is also specified) reporting an error if any element has
both characters and elements as content.
DATA_INDENT
A numeric value or white space; if this parameter is present,
it represents the indent step for elements in data mode (it
will be ignored when not in data mode). If it is white space it
will be repeated for each level of indentation.
ENCODING
A character encoding; currently this must be one of 'utf-8' or
'us-ascii'. If present, it will be used for the underlying
character encoding and as the default in the XML declaration.
CHECK_PRINT
A true or false value; if this parameter is present and its
value is true, all prints to the underlying output will be
checked for success. Failures will cause a croak rather than
being ignored.
end()
Finish creating an XML document. This method will check that the
document has exactly one document element, and that all start tags
are closed:
$writer->end();
xmlDecl([$encoding, $standalone])
Add an XML declaration to the beginning of an XML document. The
version will always be "1.0". If you provide a non-null encoding
or standalone argument, its value will appear in the declaration
(any non-null value for standalone except 'no' will automatically
be converted to 'yes'). If not given here, the encoding will be
taken from the ENCODING argument. Pass the empty string to suppress
this behaviour.
$writer->xmlDecl("UTF-8");
doctype($name, [$publicId, $systemId])
Add a DOCTYPE declaration to an XML document. The declaration must
appear before the beginning of the root element. If you provide a
publicId, you must provide a systemId as well, but you may provide
just a system ID by passing 'undef' for the publicId.
$writer->doctype("html");
comment($text)
Add a comment to an XML document. If the comment appears outside
the document element (either before the first start tag or after
the last end tag), the module will add a carriage return after it
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to improve readability. In data mode, comments will be treated as
empty tags:
$writer->comment("This is a comment");
pi($target [, $data])
Add a processing instruction to an XML document:
$writer->pi('xml-stylesheet', 'href="style.css" type="text/css"');
If the processing instruction appears outside the document element
(either before the first start tag or after the last end tag), the
module will add a carriage return after it to improve readability.
The $target argument must be a single XML name. If you provide the
$data argument, the module will insert its contents following the
$target argument, separated by a single space.
startTag($name [, $aname1 => $value1, ...])
Add a start tag to an XML document. Any arguments after the
element name are assumed to be name/value pairs for attributes: the
module will escape all '&', '<', '>', and '"' characters in the
attribute values using the predefined XML entities:
$writer->startTag('doc', 'version' => '1.0',
'status' => 'draft',
'topic' => 'AT&T');
All start tags must eventually have matching end tags.
emptyTag($name [, $aname1 => $value1, ...])
Add an empty tag to an XML document. Any arguments after the
element name are assumed to be name/value pairs for attributes (see
startTag() for details):
$writer->emptyTag('img', 'src' => 'portrait.jpg',
'alt' => 'Portrait of Emma.');
endTag([$name])
Add an end tag to an XML document. The end tag must match the
closest open start tag, and there must be a matching and properly-
nested end tag for every start tag:
$writer->endTag('doc');
If the $name argument is omitted, then the module will
automatically supply the name of the currently open element:
$writer->startTag('p');
$writer->endTag();
dataElement($name, $data [, $aname1 => $value1, ...])
Print an entire element containing only character data. This is
equivalent to
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$writer->startTag($name [, $aname1 => $value1, ...]);
$writer->characters($data);
$writer->endTag($name);
characters($data)
Add character data to an XML document. All '<', '>', and '&'
characters in the $data argument will automatically be escaped
using the predefined XML entities:
$writer->characters("Here is the formula: ");
$writer->characters("a < 100 && a > 5");
You may invoke this method only within the document element (i.e.
after the first start tag and before the last end tag).
In data mode, you must not use this method to add whitespace
between elements.
raw($data)
Print data completely unquoted and unchecked to the XML document.
For example "raw('<')" will print a literal < character. This
necessarily bypasses all well-formedness checking, and is therefore
only available in unsafe mode.
This can sometimes be useful for printing entities which are
defined for your XML format but the module doesn't know about, for
example for XHTML.
cdata($data)
As "characters()" but writes the data quoted in a CDATA section,
that is, between <![CDATA[ and ]]>. If the data to be written
itself contains ]]>, it will be written as several consecutive
CDATA sections.
cdataElement($name, $data [, $aname1 => $value1, ...])
As "dataElement()" but the element content is written as one or
more CDATA sections (see "cdata()").
setOutput($output)
Set the current output destination, as in the OUTPUT parameter for
the constructor.
getOutput()
Return the current output destination, as in the OUTPUT parameter
for the constructor.
setDataMode($mode)
Enable or disable data mode, as in the DATA_MODE parameter for the
constructor.
getDataMode()
Return the current data mode, as in the DATA_MODE parameter for the
constructor.
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setDataIndent($step)
Set the indent step for data mode, as in the DATA_INDENT parameter
for the constructor.
getDataIndent()
Return the indent step for data mode, as in the DATA_INDENT
parameter for the constructor.
Querying XML
in_element($name)
Return a true value if the most recent open element matches $name:
if ($writer->in_element('dl')) {
$writer->startTag('dt');
} else {
$writer->startTag('li');
}
within_element($name)
Return a true value if any open element matches $name:
if ($writer->within_element('body')) {
$writer->startTag('h1');
} else {
$writer->startTag('title');
}
current_element()
Return the name of the currently open element:
my $name = $writer->current_element();
This is the equivalent of
my $name = $writer->ancestor(0);
ancestor($n)
Return the name of the nth ancestor, where $n=0 for the current
open element.
Additional Namespace Support
As of 0.510, these methods may be used while writing a document.
addPrefix($uri, $prefix)
Add a preferred mapping between a Namespace URI and a prefix. See
also the PREFIX_MAP constructor parameter.
To set the default namespace, omit the $prefix parameter or set it
to ''.
removePrefix($uri)
Remove a preferred mapping between a Namespace URI and a prefix.
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forceNSDecl($uri)
Indicate that a namespace declaration for this URI should be
included with the next element to be started.
ERROR REPORTING
With the default settings, the XML::Writer module can detect several
basic XML well-formedness errors:
o Lack of a (top-level) document element, or multiple document
elements.
o Unclosed start tags.
o Misplaced delimiters in the contents of processing instructions or
comments.
o Misplaced or duplicate XML declaration(s).
o Misplaced or duplicate DOCTYPE declaration(s).
o Mismatch between the document type name in the DOCTYPE declaration
and the name of the document element.
o Mismatched start and end tags.
o Attempts to insert character data outside the document element.
o Duplicate attributes with the same name.
During Namespace processing, the module can detect the following
additional errors:
o Attempts to use PI targets or element or attribute names containing
a colon.
o Attempts to use attributes with names beginning "xmlns".
To ensure full error detection, a program must also invoke the end
method when it has finished writing a document:
$writer->startTag('greeting');
$writer->characters("Hello, world!");
$writer->endTag('greeting');
$writer->end();
This error reporting can catch many hidden bugs in Perl programs that
create XML documents; however, if necessary, it can be turned off by
providing an UNSAFE parameter:
my $writer = new XML::Writer(OUTPUT => $output, UNSAFE => 1);
AUTHOR
David Megginson <davidATmegginson.com>
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COPYRIGHT AND LICENSE
Copyright (c) 1999 by Megginson Technologies.
Copyright (c) 2003 Ed Avis <edATmembled.com>
Copyright (c) 2004-2010 Joseph Walton <joeATkafsemo.org>
Redistribution and use in source and compiled forms, with or without
modification, are permitted under any circumstances. No warranty.
SEE ALSO
XML::Parser
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