NAME¶
XML::SemanticDiff - Perl extension for comparing XML documents.
SYNOPSIS¶
use XML::SemanticDiff;
my $diff = XML::SemanticDiff->new();
foreach my $change ($diff->compare($file, $file2)) {
print "$change->{message} in context $change->{context}\n";
}
# or, if you want line numbers:
my $diff = XML::SemanticDiff->new(keeplinenums => 1);
foreach my $change ($diff->compare($file, $file2)) {
print "$change->{message} (between lines $change->{startline} and $change->{endline})\n";
}
DESCRIPTION¶
XML::SematicDiff provides a way to compare the contents and structure of two XML
documents. By default, it returns a list of hashrefs where each hashref
describes a single difference between the two docs.
METHODS¶
$obj->new([%options])¶
Ye olde object constructor.
The
new() method recognizes the following options:
- •
- keeplinenums
When this option is enabled XML::SemanticDiff will add the 'startline' and
'endline' properties (containing the line numbers for the reported
element's start tag and end tag) to each warning. For attribute events
these numbers reflect the start and end tags of the element which contains
that attribute.
- •
- keepdata
When this option is enabled XML::SemanticDiff will add the 'old_value' and
'new_value' properties to each warning. These properties contain,
surprisingly, the old and new values for the element or attribute being
reported.
In the case of missing elements or attributes (those in the first document,
not in the second) only the 'old_value' property will be defined.
Similarly, in the case of rogue elements or attributes (those in the
second document but not in the first) only the 'new_value' property will
be defined.
Note that using this option will greatly increase the amount of memory used
by your application.
- •
- diffhandler
Taking a blessed object as it's sole argument, this option provides a way to
hook the basic semantic diff engine into your own custom handler class.
Please see the section on 'CUSTOM HANDLERS' below.
- •
- ignorexpath
This option takes array of strings as argument. Strings are interpreted as
simple xpath expressions. Nodes matching these expressions are ignored
during comparison. All xpath expressions should be absolute (start with
'/').
Current implementation ignores namespaces during comparison.
@results = $differ->compare($xml1, $xml2)¶
Compares the XMLs $xml1 and $xml2 . $xml1 and $xml2 can be:
- •
- filenames
This will be considered if it is a string that does not contain newlines and
exists in the filesystem.
- •
- the XML text itself.
This will be considered if it's any kind of string.
- •
- the results of read_xml(). (see below)
This will be considered if it's a hash reference.
my $doc = read_xml($xml_location)¶
This will read the XML, process it for comparison and return it. See
compare() for how it is determined.
CUSTOM HANDLERS¶
Internally, XML::SemanticDiff uses an event-based model somewhat reminiscent of
SAX where the various 'semantic diff events' are handed off to a separate
handler class to cope with the details. For most general cases where the user
only cares about reporting the differences between two docs, the default
handler, XML::SemanticDiff::BasicHandler, will probably suffice. However, it
is often desirable to add side-effects to the diff process (updating
datastores, widget callbacks, etc.) and a custom handler allows you to be
creative with what to do about differences between two XML documents and how
those differences are reported back to the application through the
compare() method.
HANDLER METHODS¶
The following is a list of handler methods that can be used for your custom
diff-handler class.
init($self, $diff_obj)¶
The "init" method is called immediately before the the two document
HASHes are compared. The blessed XML::SemanticDiff object is passed as the
sole argument, so any values that you wish to pass from your application to
your custom handler can safely be added to the call to XML::SemanticDiff's
constructor method.
rogue_element($self, $element_name,
$todoc_element_properties)¶
The "rogue_element" method handles those cases where a given element
exists in the to-file but not in the from-file.
missing_element($self, $element_name,
$fromdoc_element_properties)¶
The "missing_element" method handles those cases where a given element
exists in the from-file but not in the to-file.
element_value($self, $element, $to_element_properties,
$fromdoc_element_properties)¶
The "element_value" method handles those cases where the text data
differs between two elements that have the same name, namespace URI, and are
at the same location in the document tree. Note that all whitespace is
normalized and the text from mixed-content elements (those containing both
text and child elements mixed together) is aggregated down to a single value.
namespace_uri($self, $element, $todoc_element_properties,
$fromdoc_element_properties)¶
The "namespace_uri" method handles case where the XML namespace URI
differs between a given element in the two documents. Note that the namespace
URI is checked, not the element prefixes since <foo:element/>
<bar:element/> and <element/> are all considered equivalent as
long as they are bound to the same namespace URI.
rogue_attribute($self, $attr_name, $element,
$todoc_element_properties)¶
The "rogue_attribute" method handles those cases where an attribute
exists in a given element the to-file but not in the from-file.
missing_attribute($self, $attr_name, $element,
$todoc_element_properties, $fromdoc_element_properties)¶
The "missing_attribute" method handles those cases where an attribute
exists in a given element exists in the from-file but not in the to-file.
attribute_value($self, $attr_name, $element,
$todoc_element_properties, $fromdoc_element_properties)¶
The "attribute_value" method handles those cases where the value of an
attribute varies between the same element in both documents.
final($self, $diff_obj)¶
The "final" method is called immediately after the two document HASHes
are compared. Like the "init" handler, it is passed a copy of the
XML::SemanticDiff object as it's sole argument.
Note that if a given method is not implemented in your custom handler class,
XML::SemanticDiff will not complain; but it means that all of those events
will be silently ignored. Consider yourself warned.
AUTHOR¶
Originally by Kip Hampton, khampton@totalcinema.com .
Further Maintained by Shlomi Fish, shlomif@iglu.org.il .
COPYRIGHT¶
Copyright (c) 2000 Kip Hampton. All rights reserved. This program is free
software; you can redistribute it and/or modify it under the same terms as
Perl itself.
Shlomi Fish hereby disclaims any implicit or explicit copyrights on this
software.
LICENSE¶
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
SEE ALSO¶
perl(1).