1XML::SAX::Writer(3) User Contributed Perl Documentation XML::SAX::Writer(3)
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6 XML::SAX::Writer - SAX2 XML Writer
7
9 version 0.57
10
12 use XML::SAX::Writer;
13 use XML::SAX::SomeDriver;
14 my $w = XML::SAX::Writer->new;
16 my $d = XML::SAX::SomeDriver->new(Handler => $w);
17 $d->parse('some options...');
19
21 Why yet another XML Writer ?
22 A new XML Writer was needed to match the SAX2 effort because quite
23 naturally no existing writer understood SAX2. My first intention had
24 been to start patching XML::Handler::YAWriter as it had previously been
25 my favourite writer in the SAX1 world.
26 However the more I patched it the more I realised that what I thought
28 was going to be a simple patch (mostly adding a few event handlers and
29 changing the attribute syntax) was turning out to be a rewrite due to
30 various ideas I'd been collecting along the way. Besides, I couldn't
31 find a way to elegantly make it work with SAX2 without breaking the
32 SAX1 compatibility which people are probably still using. There are of
33 course ways to do that, but most require user interaction which is
34 something I wanted to avoid.
35 So in the end there was a new writer. I think it's in fact better this
37 way as it helps keep SAX1 and SAX2 separated.
38
40 · new(%hash)
41 This is the constructor for this object. It takes a number of
43 parameters, all of which are optional.
44 · Output
46 This parameter can be one of several things. If it is a simple
48 scalar, it is interpreted as a filename which will be opened for
49 writing. If it is a scalar reference, output will be appended to
50 this scalar. If it is an array reference, output will be pushed
51 onto this array as it is generated. If it is a filehandle, then
52 output will be sent to this filehandle.
53 Finally, it is possible to pass an object for this parameter, in
55 which case it is assumed to be an object that implements the
56 consumer interface described later in the documentation.
57 If this parameter is not provided, then output is sent to STDOUT.
59 Note that there is no means to set an encoding layer on filehandles
61 created by this module; if this is necessary, the calling code
62 should first open a filehandle with the appropriate encoding set,
63 and pass that filehandle to this module.
64 · Escape
66 This should be a hash reference where the keys are characters
68 sequences that should be escaped and the values are the escaped
69 form of the sequence. By default, this module will escape the
70 ampersand (&), less than (<), greater than (>), double quote ("),
71 and apostrophe ('). Note that some browsers don't support the
72 ' escape used for apostrophes so that you should be careful
73 when outputting XHTML.
74 If you only want to add entries to the Escape hash, you can first
76 copy the contents of %XML::SAX::Writer::DEFAULT_ESCAPE.
77 · CommentEscape
79 Comment content often needs to be escaped differently from other
81 content. This option works exactly as the previous one except that
82 by default it only escapes the double dash (--) and that the
83 contents can be copied from %XML::SAX::Writer::COMMENT_ESCAPE.
84 · EncodeFrom
86 The character set encoding in which incoming data will be provided.
88 This defaults to UTF-8, which works for US-ASCII as well.
89 Set this to "undef" if you do not wish to decode your data.
91 · EncodeTo
93 The character set encoding in which output should be encoded.
95 Again, this defaults to UTF-8.
96 Set this to "undef" if you do not with to encode your data.
98 · QuoteCharacter
100 Set the character used to quote attributes. This defaults to single
102 quotes (') for backwards compatibility.
103
105 XML::SAX::Writer can receive pluggable consumer objects that will be in
106 charge of writing out what is formatted by this module. Setting a
107 Consumer is done by setting the Output option to the object of your
108 choice instead of to an array, scalar, or file handle as is more
109 commonly done (internally those in fact map to Consumer classes and and
110 simply available as options for your convenience).
111 If you don't understand this, don't worry. You don't need it most of
113 the time.
114 That object can be from any class, but must have two methods in its
116 API. It is also strongly recommended that it inherits from
117 XML::SAX::Writer::ConsumerInterface so that it will not break if that
118 interface evolves over time. There are examples at the end of
119 XML::SAX::Writer's code.
120 The two methods that it needs to implement are:
122 · output STRING
124 (Required)
126 This is called whenever the Writer wants to output a string
128 formatted in XML. Encoding conversion, character escaping, and
129 formatting have already taken place. It's up to the consumer to do
130 whatever it wants with the string.
131 · finalize()
133 (Optional)
135 This is called once the document has been output in its entirety,
137 during the end_document event. end_document will in fact return
138 whatever finalize() returns, and that in turn should be returned by
139 parse() for whatever parser was invoked. It might be useful if you
140 need to provide feedback of some sort.
141 Here's an example of a custom consumer. Note the extra "$" signs in
143 front of $self; the base class is optimized for the overwhelmingly
144 common case where only one data member is required and $self is a
145 reference to that data member.
146 package MyConsumer;
148 @ISA = qw( XML::SAX::Writer::ConsumerInterface );
150 use strict;
152 sub new {
154 my $self = shift->SUPER::new( my $output );
155 $$self = ''; # Note the extra '$'
157 return $self;
159 }
160 sub output {
162 my $self = shift;
163 $$self .= uc shift;
164 }
165 sub get_output {
167 my $self = shift;
168 return $$self;
169 }
170 And here is one way to use it:
172 my $c = MyConsumer->new;
174 my $w = XML::SAX::Writer->new( Output => $c );
175 ## ... send events to $w ...
177 print $c->get_output;
179 If you need to store more that one data member, pass in an array or
181 hash reference:
182 my $self = shift->SUPER::new( {} );
184 and access it like:
186 sub output {
188 my $self = shift;
189 $$self->{Output} .= uc shift;
190 }
191
193 Encoders can be plugged in to allow one to use one's favourite encoder
194 object. Presently there are two encoders: Encode and NullEncoder. They
195 need to implement two methods, and may inherit from
196 XML::SAX::Writer::NullConverter if they wish to
197 new FROM_ENCODING, TO_ENCODING
199 Creates a new Encoder. The arguments are the chosen encodings.
200 convert STRING
202 Converts that string and returns it.
203 Note that the return value of the convert method is not checked. Output
205 may be truncated if a character couldn't be converted correctly. To
206 avoid problems the encoder should take care encoding errors itself, for
207 example by raising an exception.
208
210 This module is generally used to write XML -- which it does most of the
211 time -- but just like the rest of SAX it can be used as a generic
212 framework to output data, the opposite of a non-XML SAX parser.
213 Of course there's only so much that one can abstract, so depending on
215 your format this may or may not be useful. If it is, you'll need to
216 know the following API (and probably to have a look inside
217 "XML::SAX::Writer::XML", the default Writer).
218 init
220 Called before the writing starts, it's a chance for the subclass to
221 do some initialisation if it needs it.
222 setConverter
224 This is used to set the proper converter for character encodings.
225 The default implementation should suffice but you can override it.
226 It must set "$self->{Encoder}" to an Encoder object. Subclasses
227 *should* call it.
228 setConsumer
230 Same as above, except that it is for the Consumer object, and that
231 it must set "$self->{Consumer}".
232 setEscaperRegex
234 Will initialise the escaping regex "$self->{EscaperRegex}" based on
235 what is needed.
236 escape STRING
238 Takes a string and escapes it properly.
239 setCommentEscaperRegex and escapeComment STRING
241 These work exactly the same as the two above, except that they are
242 meant to operate on comment contents, which often have different
243 escaping rules than those that apply to regular content.
244
246 - proper UTF-16 handling
247 - the formatting options need to be developed.
249 - test, test, test (and then some tests)
251 - doc, doc, doc (actually this part is in better shape)
253 - remove the xml_decl and replace it with intelligent logic, as
255 discussed on perl-xml
256 - make a the Consumer selecting code available in the API, to avoid
258 duplicating
259 - add an Apache output Consumer, triggered by passing $r as Output
261
263 Michael Koehne (XML::Handler::YAWriter) for much inspiration and Barrie
264 Slaymaker for the Consumer pattern idea, the coderef output option and
265 miscellaneous bugfixes and performance tweaks. Of course the usual
266 suspects (Kip Hampton and Matt Sergeant) helped in the usual ways.
267
269 XML::SAX::*
270
272 · Robin Berjon <robin@knowscape.com>
273 · Chris Prather <chris@prather.org>
275
277 This software is copyright (c) 2014 by Robin Berjon.
278 This is free software; you can redistribute it and/or modify it under
280 the same terms as the Perl 5 programming language system itself.
281perl v5.32.0 2020-07-28 XML::SAX::Writer(3)