How do I modify version number in XML doc - path to pass to Twig?

[Sherman Willden]

I am trying to use Perl's XML::Twig to modify a version number in an
XML document. At the very end of this posting is an excerpt from the
xml document. Just before the xml excerpt is the Perl code I am trying
to use. The Xpath part of the script functions well.

I think I need help determining the @field entry. I have tried
//property[\@name='version']/string, version/string, and string. I get
a "Can't modify non-lvalue subroutine call at C:\business
copy\xml_try_scripts\try_xpath.pl line 26." Error which I think is
caused by $field[] being null.

Any ideas about what the @field value should be?

Thanks;

Sherman

#!/usr/bin/perl -w

use strict;
use XML::XPath;
use XML::XPath::XMLParser;
use XML::Twig;

# create an object to parse the file and field XPath queries
# my $xpath = XML::XPath->new( filename => shift @ARGV );
my $xpath = XML::XPath->new( filename => "Product.iap_xml" );

# apply the path from the command line and get back a list matches
my $field;
my @field = "string";

my $old_value = $xpath->find(
"//property[\@name='version']/string/text()" );
## $old_value returns 2.20.0.0
# print each node in the list
# foreach my $node ( $old_value->get_nodelist ) {
# print XML::XPath::XMLParser::as_string( $node ) . "\n";
#}

my $new_value = 2.20.0.12;
my $t = new XML::Twig( TwigRoots =>
{ $field[string() = $old_value] => \&update },
TwigPrintOutsideRoots => 1,);
$t->parsefile( 'BC_HA.iap_xml' );
$t->flush;

sub update
{
my( $t, $field_elt)= @_;
$field_elt->set_text( $new_value);
$field_elt->print;
}
## End of perl script and start of XML document

<?xml version="1.0" encoding="UTF-8"?>
Some comment stuff removed
<InstallAnywhere_Deployment_Project increments="nnnn">
<essentialScriptInfo>
<versionID major="n" minor="n" revision="-1"/>
<editionID> lots of numbers removed </editionID>
<scriptID> lots of numbers removed </scriptID>
<buildID> lots of numbers removed </buildID>
<authorizationID>lots of numbers removed</authorizationID>
</essentialScriptInfo>
<installationObjects uniqueObjects="307">
<object class="com.zerog.ia.installer.Installer" objectID="some
numbers removed">
<property name="classpath">
<object class="java.util.Vector"/>
</property>
lots of stuff removed
<property name="RPMSpec">
<object class="com.zerog.ia.installer.RPMSpec" objectID="some
numbers removed">
<property name="enabled">
<boolean>true</boolean>
</property>
<property name="name">
<string><![CDATA[Our Product 2.2 Product Sub Name]]></string>
</property>
<property name="version">
<string><![CDATA[2.20.0.0]]></string>
</property>
<property name="release">
<string><![CDATA[2.20.0.0]]></string>
</property>
<property name="description">
<string><![CDATA[]]></string>
</property>
<property name="summary">
<string><![CDATA[<none>]]></string>
</property>
<property name="copyright">
<string><![CDATA[2003]]></string>
</property>
<property name="url">
<string><![CDATA[http://www.this.com]]></string>
</property>
<property name="distribution">
<string><![CDATA[<none>]]></string>
</property>
<property name="vendor">
<string><![CDATA[HP]]></string>
</property>
<property name="group">
<string><![CDATA[Applications/System]]></string>
</property>
<property name="packager">
<string><![CDATA[]]></string>
</property>
</object>
</property>
<property name="buildSettings">
<object class="java.util.Properties">

Lots of stuff to end of doucument removed

 

[Michel Rodriguez]

I am trying to use Perl's XML::Twig to modify a version number in an
XML document. At the very end of this posting is an excerpt from the
xml document. Just before the xml excerpt is the Perl code I am trying
to use. The Xpath part of the script functions well.

my $new_value = 2.20.0.12;
my $t = new XML::Twig( TwigRoots =>
{ $field[string() = $old_value] => \&update },
TwigPrintOutsideRoots => 1,);
$t->parsefile( 'BC_HA.iap_xml' );
$t->flush;

I think the problem comes from the fact that $field[string() = $old_value]
is not quoted, which means that it will be executed, and string()=
$old_value will give the error message you get.

The XPath expression is a simple string, which needs to be quoted, the
attribute value needs to be quoted in the expression, and finally you need
to escap the [ after $field or Perl thinks that field is an array.

qq{$field\[string() = "$old_value"]}

That said, this won't work either: twig_roots needs to be able to determine
whether an element will be processed right when the element start, not
later when you can use the string() value.

The best you can do is probably to use $field for the twig_roots and then
test on the content in the handler.

Here is a version that builds the tree for all elements, but that flushes
them as soon as possible:


my $field= 'string';
my $old_value = '2.20.0.0';
my $new_value = '2.20.0.12';

my $t = new XML::Twig( twig_handlers =>
{ qq{$field\[string() = "$old_value"]} => \&update, # process
__default__ => sub { $_[0]->flush; }, # flush anything else
},
pretty_print => 'record_c',
);
$t->parse( \*DATA );
$t->flush;

sub update
{
my( $t, $field_elt)= @_;
# if you want the version number to be in a CDATA section
# then set_content is not enough
if( my $cdata= $field_elt->first_child_is( '#CDATA'))
{ $cdata->set_cdata( $new_value); }
else
{ $field_elt->set_text( $new_value); }
}


Michel Rodriguez
Perl &amp; XML
http://xmltwig.com

 

[sherman willden]

Thank you, Michael. I will try this today.

Sherman

 

[Sherman Willden]

Thanks, Michael, for your response earlier and the code works, the
values are modified, and the text stream is output to the screen.

My question is how do I get a well-formed XML document from the
results? I tried printing to a file handle ( C:\temp\twig_tmp.xml )
but that didn't work. Below is the code that outputs the results to
the screen.

To further explain, I have file xyz.xml. I want to modify one value in
the xyz.xml file and have a working xyz.xml file after the
modification.

I am sure that I missed the answer when reading Michael's site, Perl
and XML, and the twig documentation. Can someone provide a reference
to the paragraph(s) that explains what I missed?

Thanks;

Sherman

#!/usr/bin/perl -w

use strict;
use XML::XPath;
use XML::XPath::XMLParser;
use XML::Twig;

my $field= 'string';
my $old_value = '2.20.0.0';
my $new_value = '2.20.0.12';

if ( -f "C:/temp/twig_tmp.xml" ) {
chmod(0777, "C:/temp/twig_tmp.xml");
unlink("C:/temp/twig_tmp.xml");
}

#open(TMPFLE, ">>c:/temp/twig_tmp.xml");

my $t = new XML::Twig( twig_handlers =>
{ qq{$field\[string() = "$old_value"] } => \&update, # process
__default__ => sub { $_[0]->flush; }, # flush anything
else
},
pretty_print => 'record_c',);
$t->parsefile( 'BC_HA.iap_xml' );
#$t->print( \*TMPFLE );
$t->flush;

#close(TMPFLE);

sub update
{
my( $t, $field_elt)= @_;
# if you want the version number to be in a CDATA section
# then set_content is not enough
if( my $cdata= $field_elt->first_child_is( '#CDATA'))
{ $cdata->set_cdata( $new_value); }
else
{ $field_elt->set_text( $new_value); }
}

 

[Sherman Willden]

I have it now and my apologies to Michel Rodriguez if I gave any
indication that it didn't work.

I was comparing the look and file size of the output file which were
different from the original file since I was using record_c. After
posting this I ran a parser and the file was xml compliant. After I
used indented_c the file size and appearance was the same as the
original file.

Sherman