XML/XUpdate/XSLT.pm

##############################################################################
#
# Perl module: XML::XUpdate::XSLT
#
# By Andreas Motl, andreas.motl@ilo.de
#
#    $Id: XSLT.pm,v 1.4 2003/05/01 23:40:32 joko Exp $
#
#    $Log: XSLT.pm,v $
#    Revision 1.4  2003/05/01 23:40:32  joko
#    minor update: commented debugging part
#
#    Revision 1.3  2003/05/01 20:11:49  joko
#    * added pod from xupdate.pl
#    - extracted xml to external files
#
#    Revision 1.1  2003/04/30 02:36:32  joko
#    initial commit
#
#
###############################################################################

=pod


=head1 NAME

  XML::XUpdate::XSLT - A perl module for updating xml documents using XUpdate via XSLT.


=head3 Overview

  This is not the same xupdate currently available from CPAN at
  http://search.cpan.org/author/PAJAS/XML-XUpdate-LibXML-0.4.0/xupdate .
  
  Its intention - however - is identical:
  xupdate - Process XUpdate commands against an XML document.


=head3 Their implementations differ:

    1. xupdate (by Petr Pajas) uses ...
    XML::XUpdate::LibXML - Simple implementation of XUpdate format 
    
    ... which is based on XML::LibXML which in turn is:
    [...]
    This module is an interface to the gnome libxml2 DOM parser (no SAX parser support yet), 
    and the DOM tree. It also provides an XML::XPath-like findnodes() interface, providing 
    access to the XPath API in libxml2. 
    [...]

    2. This xupdate attempts to implement the XUpdate specs using XSLT only.
    

=head3 Yet another xupdate - facts in short:

  S: It would be nice to have a pure perl thingy which does (almost) the same stuff....
  
  Q: Can we achieve compliance with its (XML::XUpdate::LibXML) API? (or just a subset ....)
  
  Q: Can we achieve the processing using CPAN's XML::XSLT?
  S: Proposal: XML::XUpdate::XSLT!?
  
  Q: Can we mimic/use the interface of the - already established - 'xupdate' program???
  
  Q: Should we follow the CRUD path first?
      (CRUD is the acronym for the datastore action primitives: Create, Retrieve, Update, Delete)
  S?: Proposal: XML::XUpdate::XSLT::API uses XML::XUpdate::XSLT::CRUD


=head4 Todo

  o What about proper encoding? (ISO-8859-1 or UTF-8)
  o Is it possible to create the required "xsl_template.xml" at runtime via XSL itself?
  o Cache contents of external files (*.xml). Performance!
  o Can exception / error-code handling be improved somehow?
      Esp.: It would be interesting, if the XUpdate payload actually could be applied, or not...
  

=cut


######################################################################
package XML::XUpdate::XSLT;
######################################################################

use strict;
use warnings;

use Data::Dumper;
use File::Basename;
use XML::XSLT 0.41;
use XML::XUpdate::Rewrite;

# Namespace constants

use constant NS_XUPDATE         => 'http://www.xmldb.org/xupdate';

use vars qw ( $VERSION );

$VERSION = '0.01';


######################################################################
# PUBLIC DEFINITIONS

sub new {
  my $class = shift;
  my $self = bless {}, $class;
  my $args = $self->__parse_args(@_);
  
  $self->{DEBUG} = $args->{debug};
  $self->{WARNINGS} = $args->{warnings};

  $self->__init_default_stylesheets();

  return $self;

}

sub get_stylesheet {
  my $self = shift;
  my $name = shift;
  return $self->{XML}->{xsl}->{$name};
}

sub set_stylesheet {
  my $self = shift;
  my $name = shift;
  my $xml = shift;
  my $options = shift;
  if ($options->{encap}) {
    my $template = $self->__slurp_file("xsl_template.xml");
    # FIXME! What about the quirky? Is there a better one?
    $template =~ s!<xsl:quirky_placeholder />!$xml!;
    $xml = $template;
  }
  $self->{XML}->{xsl}->{$name} = $xml;
}

sub open_document {
  my $self = shift;
  my $xml = shift;
  # FIXME: check for filename, filehandle and URL (etc.)
  $self->{XML}->{document} = $xml;
}

sub open_xupdate {
  my $self = shift;
  my $xml = shift;
  # FIXME: check for filename, filehandle and U<RL (etc.)
  $self->{XML}->{xupdate} = $xml;
}

sub process {
  my $self = shift;
  $self->_calculate();
  $self->_apply();
}

# First, translate the xupdate payload to xsl.
# FIXME: do DOM only! (don't use "->toString")
sub _calculate {
  my $self = shift;
  $self->{XSLT_ENGINE_PREP} = XML::XSLT->new(
    Source => $self->get_stylesheet("xupdate2xsl"), 
    debug => $self->{DEBUG},
    warnings => $self->{WARNINGS}
  );
  $self->{XSLT_ENGINE_PREP}->open_xml( $self->{XML}->{xupdate} );
  $self->{XSLT_ENGINE_PREP}->process();
  $self->set_stylesheet( "_worker", $self->{XSLT_ENGINE_PREP}->toString(), { encap => 1 } );
}

# After that, use this worker xsl to actually apply the changes to the original document.
# FIXME: do DOM only!
sub _apply {
  my $self = shift;
  
  # debug - print the calculated xsl on STDERR
  #print STDERR $self->get_stylesheet("_worker"), "\n";
  
  #return;
  $self->{XSLT_ENGINE_LIVE} = XML::XSLT->new(
    Source => $self->get_stylesheet("_worker"), 
    debug => $self->{DEBUG},
    warnings => $self->{WARNINGS}
  );
  $self->{XSLT_ENGINE_LIVE}->open_xml( $self->{XML}->{document} );
  $self->{XSLT_ENGINE_LIVE}->process();
  $self->{XML}->{result} = $self->{XSLT_ENGINE_LIVE}->toString();
}  
  
sub toString {
  my $self = shift;
  
  # use rest of argument list as hash of option values
  my $options = {@_};
  
  # short circuit - just return what we have - don't modify anything
  return $self->{XML}->{result} unless $options and $options->{rewrite};
  
  # Rewrite the xml document with certain engine to desired style.
  # 'engine' defaults to "XMLParser" if not specified.
  my $rewrite = XML::XUpdate::Rewrite->new( style => $options->{mode}, engine => $options->{using} );
  $rewrite->set_document( $self->{XML}->{result} );
  # TODO: Implement a configurable fallback here to return the un-rewritten payload if desired.
  $rewrite->process() or die(__PACKAGE__ . ": Error while rewriting XML document.");
  return $rewrite->get_document();
}


######################################################################
# AUXILIARY METHODS

# Argument list parsing.
# ... from XML::XUpdate::LibXML (w/o backwards compatibility hook).
# Could this make up a Class::AutoFill::__read_arglist which transparently 
# makes object attributes from constructor arguments in a configurable way?
sub __parse_args {
  my $self = shift;
  my %args;

  if ( @_ % 2 ) {
    $args{dummy} = shift;
    %args = (%args, @_);
  } else {
    %args = @_;
  }

  return \%args;
}


sub __init_default_stylesheets {
  my $self = shift;
  if (my $payload = $self->__slurp_file("xupdate2xsl.xml")) {
    $self->{XML}->{xsl}->{xupdate2xsl} = $payload;
  }
}

sub __slurp_file {
  my $self = shift;
  my $filename = shift;
  
  # does file exist?
  if (! -e $filename) {
    $filename = dirname(__FILE__) . "/$filename";
    if (! -e $filename) {
      die("File $filename does not exist.");
    }
  }
  
  open(FH, "<" . $filename);
  my @lines = <FH>;
  my $content = join("", @lines);
  close(FH);
  return $content;
}

1;
__END__
1	joko	1.1	##############################################################################
2			#
3			# Perl module: XML::XUpdate::XSLT
4			#
5			# By Andreas Motl, andreas.motl@ilo.de
6			#
7	joko	1.5	# $Id: XSLT.pm,v 1.4 2003/05/01 23:40:32 joko Exp $
8	joko	1.1	#
9			# $Log: XSLT.pm,v $
10	joko	1.5	# Revision 1.4 2003/05/01 23:40:32 joko
11			# minor update: commented debugging part
12			#
13	joko	1.4	# Revision 1.3 2003/05/01 20:11:49 joko
14			# * added pod from xupdate.pl
15			# - extracted xml to external files
16			#
17	joko	1.2	# Revision 1.1 2003/04/30 02:36:32 joko
18			# initial commit
19			#
20	joko	1.1	#
21			###############################################################################
22
23	joko	1.3	=pod
24
25
26	joko	1.1	=head1 NAME
27
28	joko	1.5	XML::XUpdate::XSLT - A perl module for updating xml documents using XUpdate via XSLT.
29	joko	1.1
30	joko	1.3
31			=head3 Overview
32
33			This is not the same xupdate currently available from CPAN at
34			http://search.cpan.org/author/PAJAS/XML-XUpdate-LibXML-0.4.0/xupdate .
35
36			Its intention - however - is identical:
37			xupdate - Process XUpdate commands against an XML document.
38
39
40			=head3 Their implementations differ:
41
42			1. xupdate (by Petr Pajas) uses ...
43			XML::XUpdate::LibXML - Simple implementation of XUpdate format
44
45			... which is based on XML::LibXML which in turn is:
46			[...]
47			This module is an interface to the gnome libxml2 DOM parser (no SAX parser support yet),
48			and the DOM tree. It also provides an XML::XPath-like findnodes() interface, providing
49			access to the XPath API in libxml2.
50			[...]
51
52			2. This xupdate attempts to implement the XUpdate specs using XSLT only.
53
54
55			=head3 Yet another xupdate - facts in short:
56
57			S: It would be nice to have a pure perl thingy which does (almost) the same stuff....
58
59			Q: Can we achieve compliance with its (XML::XUpdate::LibXML) API? (or just a subset ....)
60
61			Q: Can we achieve the processing using CPAN's XML::XSLT?
62			S: Proposal: XML::XUpdate::XSLT!?
63
64			Q: Can we mimic/use the interface of the - already established - 'xupdate' program???
65
66	joko	1.5	Q: Should we follow the CRUD path first?
67			(CRUD is the acronym for the datastore action primitives: Create, Retrieve, Update, Delete)
68	joko	1.3	S?: Proposal: XML::XUpdate::XSLT::API uses XML::XUpdate::XSLT::CRUD
69
70
71			=head4 Todo
72
73			o What about proper encoding? (ISO-8859-1 or UTF-8)
74			o Is it possible to create the required "xsl_template.xml" at runtime via XSL itself?
75			o Cache contents of external files (*.xml). Performance!
76	joko	1.5	o Can exception / error-code handling be improved somehow?
77			Esp.: It would be interesting, if the XUpdate payload actually could be applied, or not...
78	joko	1.3
79
80	joko	1.1	=cut
81
82
83			######################################################################
84			package XML::XUpdate::XSLT;
85			######################################################################
86
87			use strict;
88			use warnings;
89
90	joko	1.5	use Data::Dumper;
91			use File::Basename;
92	joko	1.1	use XML::XSLT 0.41;
93	joko	1.5	use XML::XUpdate::Rewrite;
94	joko	1.1
95			# Namespace constants
96
97			use constant NS_XUPDATE => 'http://www.xmldb.org/xupdate';
98
99			use vars qw ( $VERSION );
100
101	joko	1.3	$VERSION = '0.01';
102	joko	1.1
103
104			######################################################################
105			# PUBLIC DEFINITIONS
106
107			sub new {
108			my $class = shift;
109			my $self = bless {}, $class;
110			my $args = $self->__parse_args(@_);
111
112	joko	1.2	$self->{DEBUG} = $args->{debug};
113			$self->{WARNINGS} = $args->{warnings};
114
115	joko	1.3	$self->__init_default_stylesheets();
116	joko	1.1
117	joko	1.2	return $self;
118	joko	1.1
119	joko	1.2	}
120	joko	1.1
121	joko	1.2	sub get_stylesheet {
122			my $self = shift;
123			my $name = shift;
124			return $self->{XML}->{xsl}->{$name};
125	joko	1.1	}
126
127	joko	1.2	sub set_stylesheet {
128	joko	1.1	my $self = shift;
129			my $name = shift;
130	joko	1.2	my $xml = shift;
131			my $options = shift;
132			if ($options->{encap}) {
133	joko	1.3	my $template = $self->__slurp_file("xsl_template.xml");
134			# FIXME! What about the quirky? Is there a better one?
135			$template =~ s!<xsl:quirky_placeholder />!$xml!;
136			$xml = $template;
137	joko	1.2	}
138			$self->{XML}->{xsl}->{$name} = $xml;
139	joko	1.1	}
140
141			sub open_document {
142			my $self = shift;
143			my $xml = shift;
144			# FIXME: check for filename, filehandle and URL (etc.)
145			$self->{XML}->{document} = $xml;
146			}
147
148			sub open_xupdate {
149			my $self = shift;
150			my $xml = shift;
151	joko	1.5	# FIXME: check for filename, filehandle and U<RL (etc.)
152	joko	1.1	$self->{XML}->{xupdate} = $xml;
153			}
154
155			sub process {
156			my $self = shift;
157	joko	1.2	$self->_calculate();
158			$self->_apply();
159	joko	1.1	}
160
161	joko	1.2	# First, translate the xupdate payload to xsl.
162	joko	1.5	# FIXME: do DOM only! (don't use "->toString")
163	joko	1.2	sub _calculate {
164			my $self = shift;
165			$self->{XSLT_ENGINE_PREP} = XML::XSLT->new(
166			Source => $self->get_stylesheet("xupdate2xsl"),
167			debug => $self->{DEBUG},
168			warnings => $self->{WARNINGS}
169			);
170			$self->{XSLT_ENGINE_PREP}->open_xml( $self->{XML}->{xupdate} );
171			$self->{XSLT_ENGINE_PREP}->process();
172			$self->set_stylesheet( "_worker", $self->{XSLT_ENGINE_PREP}->toString(), { encap => 1 } );
173			}
174
175			# After that, use this worker xsl to actually apply the changes to the original document.
176			# FIXME: do DOM only!
177			sub _apply {
178			my $self = shift;
179	joko	1.4
180			# debug - print the calculated xsl on STDERR
181			#print STDERR $self->get_stylesheet("_worker"), "\n";
182
183	joko	1.2	#return;
184			$self->{XSLT_ENGINE_LIVE} = XML::XSLT->new(
185			Source => $self->get_stylesheet("_worker"),
186			debug => $self->{DEBUG},
187			warnings => $self->{WARNINGS}
188			);
189			$self->{XSLT_ENGINE_LIVE}->open_xml( $self->{XML}->{document} );
190			$self->{XSLT_ENGINE_LIVE}->process();
191			$self->{XML}->{result} = $self->{XSLT_ENGINE_LIVE}->toString();
192			}
193
194	joko	1.1	sub toString {
195			my $self = shift;
196	joko	1.5
197			# use rest of argument list as hash of option values
198			my $options = {@_};
199
200			# short circuit - just return what we have - don't modify anything
201			return $self->{XML}->{result} unless $options and $options->{rewrite};
202
203			# Rewrite the xml document with certain engine to desired style.
204			# 'engine' defaults to "XMLParser" if not specified.
205			my $rewrite = XML::XUpdate::Rewrite->new( style => $options->{mode}, engine => $options->{using} );
206			$rewrite->set_document( $self->{XML}->{result} );
207			# TODO: Implement a configurable fallback here to return the un-rewritten payload if desired.
208			$rewrite->process() or die(__PACKAGE__ . ": Error while rewriting XML document.");
209			return $rewrite->get_document();
210	joko	1.1	}
211	joko	1.5
212	joko	1.1
213			######################################################################
214			# AUXILIARY METHODS
215
216	joko	1.5	# Argument list parsing.
217			# ... from XML::XUpdate::LibXML (w/o backwards compatibility hook).
218			# Could this make up a Class::AutoFill::__read_arglist which transparently
219			# makes object attributes from constructor arguments in a configurable way?
220	joko	1.1	sub __parse_args {
221			my $self = shift;
222			my %args;
223
224	joko	1.5	if ( @_ % 2 ) {
225	joko	1.1	$args{dummy} = shift;
226			%args = (%args, @_);
227			} else {
228			%args = @_;
229			}
230
231			return \%args;
232			}
233
234
235	joko	1.3	sub __init_default_stylesheets {
236			my $self = shift;
237			if (my $payload = $self->__slurp_file("xupdate2xsl.xml")) {
238			$self->{XML}->{xsl}->{xupdate2xsl} = $payload;
239			}
240			}
241
242			sub __slurp_file {
243	joko	1.1	my $self = shift;
244	joko	1.3	my $filename = shift;
245	joko	1.1
246	joko	1.3	# does file exist?
247			if (! -e $filename) {
248			$filename = dirname(__FILE__) . "/$filename";
249			if (! -e $filename) {
250	joko	1.5	die("File $filename does not exist.");
251	joko	1.3	}
252			}
253	joko	1.1
254	joko	1.3	open(FH, "<" . $filename);
255			my @lines = <FH>;
256			my $content = join("", @lines);
257			close(FH);
258			return $content;
259	joko	1.1	}
260
261			1;
262			__END__
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