Provided by: libxml-sax-writer-perl_0.57-2_all 
NAME
XML::SAX::Writer - SAX2 XML Writer
VERSION
version 0.57
SYNOPSIS
use XML::SAX::Writer;
use XML::SAX::SomeDriver;
my $w = XML::SAX::Writer->new;
my $d = XML::SAX::SomeDriver->new(Handler => $w);
$d->parse('some options...');
DESCRIPTION
Why yet another XML Writer ?
A new XML Writer was needed to match the SAX2 effort because quite naturally no existing
writer understood SAX2. My first intention had been to start patching
XML::Handler::YAWriter as it had previously been my favourite writer in the SAX1 world.
However the more I patched it the more I realised that what I thought was going to be a
simple patch (mostly adding a few event handlers and changing the attribute syntax) was
turning out to be a rewrite due to various ideas I'd been collecting along the way.
Besides, I couldn't find a way to elegantly make it work with SAX2 without breaking the
SAX1 compatibility which people are probably still using. There are of course ways to do
that, but most require user interaction which is something I wanted to avoid.
So in the end there was a new writer. I think it's in fact better this way as it helps
keep SAX1 and SAX2 separated.
METHODS
• new(%hash)
This is the constructor for this object. It takes a number of parameters, all of which
are optional.
• Output
This parameter can be one of several things. If it is a simple scalar, it is
interpreted as a filename which will be opened for writing. If it is a scalar
reference, output will be appended to this scalar. If it is an array reference, output
will be pushed onto this array as it is generated. If it is a filehandle, then output
will be sent to this filehandle.
Finally, it is possible to pass an object for this parameter, in which case it is
assumed to be an object that implements the consumer interface described later in the
documentation.
If this parameter is not provided, then output is sent to STDOUT.
Note that there is no means to set an encoding layer on filehandles created by this
module; if this is necessary, the calling code should first open a filehandle with the
appropriate encoding set, and pass that filehandle to this module.
• Escape
This should be a hash reference where the keys are characters sequences that should be
escaped and the values are the escaped form of the sequence. By default, this module
will escape the ampersand (&), less than (<), greater than (>), double quote ("), and
apostrophe ('). Note that some browsers don't support the ' escape used for
apostrophes so that you should be careful when outputting XHTML.
If you only want to add entries to the Escape hash, you can first copy the contents of
%XML::SAX::Writer::DEFAULT_ESCAPE.
• CommentEscape
Comment content often needs to be escaped differently from other content. This option
works exactly as the previous one except that by default it only escapes the double
dash (--) and that the contents can be copied from %XML::SAX::Writer::COMMENT_ESCAPE.
• EncodeFrom
The character set encoding in which incoming data will be provided. This defaults to
UTF-8, which works for US-ASCII as well.
Set this to "undef" if you do not wish to decode your data.
• EncodeTo
The character set encoding in which output should be encoded. Again, this defaults to
UTF-8.
Set this to "undef" if you do not with to encode your data.
• QuoteCharacter
Set the character used to quote attributes. This defaults to single quotes (') for
backwards compatibility.
THE CONSUMER INTERFACE
XML::SAX::Writer can receive pluggable consumer objects that will be in charge of writing
out what is formatted by this module. Setting a Consumer is done by setting the Output
option to the object of your choice instead of to an array, scalar, or file handle as is
more commonly done (internally those in fact map to Consumer classes and and simply
available as options for your convenience).
If you don't understand this, don't worry. You don't need it most of the time.
That object can be from any class, but must have two methods in its API. It is also
strongly recommended that it inherits from XML::SAX::Writer::ConsumerInterface so that it
will not break if that interface evolves over time. There are examples at the end of
XML::SAX::Writer's code.
The two methods that it needs to implement are:
• output STRING
(Required)
This is called whenever the Writer wants to output a string formatted in XML. Encoding
conversion, character escaping, and formatting have already taken place. It's up to
the consumer to do whatever it wants with the string.
• finalize()
(Optional)
This is called once the document has been output in its entirety, during the
end_document event. end_document will in fact return whatever finalize() returns, and
that in turn should be returned by parse() for whatever parser was invoked. It might
be useful if you need to provide feedback of some sort.
Here's an example of a custom consumer. Note the extra "$" signs in front of $self; the
base class is optimized for the overwhelmingly common case where only one data member is
required and $self is a reference to that data member.
package MyConsumer;
@ISA = qw( XML::SAX::Writer::ConsumerInterface );
use strict;
sub new {
my $self = shift->SUPER::new( my $output );
$$self = ''; # Note the extra '$'
return $self;
}
sub output {
my $self = shift;
$$self .= uc shift;
}
sub get_output {
my $self = shift;
return $$self;
}
And here is one way to use it:
my $c = MyConsumer->new;
my $w = XML::SAX::Writer->new( Output => $c );
## ... send events to $w ...
print $c->get_output;
If you need to store more that one data member, pass in an array or hash reference:
my $self = shift->SUPER::new( {} );
and access it like:
sub output {
my $self = shift;
$$self->{Output} .= uc shift;
}
THE ENCODER INTERFACE
Encoders can be plugged in to allow one to use one's favourite encoder object. Presently
there are two encoders: Encode and NullEncoder. They need to implement two methods, and
may inherit from XML::SAX::Writer::NullConverter if they wish to
new FROM_ENCODING, TO_ENCODING
Creates a new Encoder. The arguments are the chosen encodings.
convert STRING
Converts that string and returns it.
Note that the return value of the convert method is not checked. Output may be truncated
if a character couldn't be converted correctly. To avoid problems the encoder should take
care encoding errors itself, for example by raising an exception.
CUSTOM OUTPUT
This module is generally used to write XML -- which it does most of the time -- but just
like the rest of SAX it can be used as a generic framework to output data, the opposite of
a non-XML SAX parser.
Of course there's only so much that one can abstract, so depending on your format this may
or may not be useful. If it is, you'll need to know the following API (and probably to
have a look inside "XML::SAX::Writer::XML", the default Writer).
init
Called before the writing starts, it's a chance for the subclass to do some
initialisation if it needs it.
setConverter
This is used to set the proper converter for character encodings. The default
implementation should suffice but you can override it. It must set "$self->{Encoder}"
to an Encoder object. Subclasses *should* call it.
setConsumer
Same as above, except that it is for the Consumer object, and that it must set
"$self->{Consumer}".
setEscaperRegex
Will initialise the escaping regex "$self->{EscaperRegex}" based on what is needed.
escape STRING
Takes a string and escapes it properly.
setCommentEscaperRegex and escapeComment STRING
These work exactly the same as the two above, except that they are meant to operate on
comment contents, which often have different escaping rules than those that apply to
regular content.
TODO
- proper UTF-16 handling
- the formatting options need to be developed.
- test, test, test (and then some tests)
- doc, doc, doc (actually this part is in better shape)
- remove the xml_decl and replace it with intelligent logic, as
discussed on perl-xml
- make a the Consumer selecting code available in the API, to avoid
duplicating
- add an Apache output Consumer, triggered by passing $r as Output
CREDITS
Michael Koehne (XML::Handler::YAWriter) for much inspiration and Barrie Slaymaker for the
Consumer pattern idea, the coderef output option and miscellaneous bugfixes and
performance tweaks. Of course the usual suspects (Kip Hampton and Matt Sergeant) helped in
the usual ways.
SEE ALSO
XML::SAX::*
AUTHORS
• Robin Berjon <robin@knowscape.com>
• Chris Prather <chris@prather.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2014 by Robin Berjon.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.