问题
I am comparing two XML files. If I find a node missing in one of the files I want to insert it into the other file. Here is how I have been trying it:
my $out_file = 'fbCI_report.xml';
open my $fh_out, '>>', $out_file or die "Can't open $out_file for writing: $!";
my $currentReport = XML::Twig->new( pretty_print => 'indented' );
$currentReport->parsefile($path_to_currentReport);
print "Loaded current report.\n";
my $newReport = XML::Twig->new( pretty_print => 'indented' );
$newReport->parsefile($path_to_newReport);
print "Loaded new report.\n";
my $currentRoot = $currentReport->root; # get the root
my $currentBuilds = $currentRoot->first_child(); # get the builds node
my $currentXCR = $currentBuilds->first_child(); # get the xcr node
my $newRoot = $newReport->root; # get the root
my $newBuilds = $newRoot->first_child(); # get the builds node
my $newXCR = $newBuilds->first_child(); # get the xcr node
my @currentXCRarray = $currentBuilds->children('xcr');
my @newXCRarray = $newBuilds->children('xcr');
my $numberOfxcr = $newBuilds->children_count();
foreach my $currentXCRmod ( @currentXCRarray ) {
my $currentID = $currentXCRmod->att("id");
foreach my $newXCRmod (@newXCRarray) {
my $newID = $newXCRmod->att("id");
if ( $newID == $currentID ) {
last;
}
elsif ( $count == $numberOfxcr && $newID != $currentID ) {
my $insert = $currentBuilds->insert_new_elt($newXCRmod);
print "XCR does not exist in current report, adding it..\n";
}
$count++;
}
}
print $fh_out $currentReport->sprint();
close $fh_out;
However this does not insert the node with the corresponding children but what I guess is the reference to the node: <XML::Twig::Elt=HASH(0x326efe0)/>. Is there a way to insert the node properly? I have yet to find anything on the CPAN site.
Sample data, current.xml:
<project>
<builds>
<xcr id="13367" buildable="false">
<artifact name="rb"/>
<artifact name="syca"/>
</xcr>
<xcr id="13826" buildable="false">
<artifact name="dcs"/>
</xcr>
<\builds>
<\project>
new.xml:
<project>
<builds>
<xcr id="13367" buildable="false">
<artifact name="rb"/>
<artifact name="syca"/>
</xcr>
<xcr id="13826" buildable="false">
<artifact name="dcs"/>
</xcr>
<xcr id="10867" buildable="true">
<artifact name="smth"/>
<artifact name="top"/>
<artifact name="tree"/>
</xcr>
<\builds>
<\project>
回答1:
You're right - that's the stringified text of an XML::Twig::Elt.
The problem is - insert_new_elt creates a new element. So what you're doing is effectively, "printing" the element id ( XML::Twig::Elt=HASH(0x326efe0)) and creating a new node called that.
But you don't want to do that - you're wanting to copy an existing one.
So I would suggest what you want to do is:
my $copied_elt = $currentXCRmod -> copy;
$copied_elt -> paste ( last_child => $currentBuilds );
Which will transfer the element (into the 'last_child' position).
Although I'd suggest that your loop is perhaps something you could improve on too - I would suggest you look at a twig_handler, to check which ID's exist in the file at parse:
my %seen_id;
sub collect_ids {
my ( $twig, $element ) = @_;
$seen_id { $element->att('id') } ++;
}
And then call this at parse time:
my $currentReport = XML::Twig->new(twig_handlers => { 'xcr' => \&collect_ids},
pretty_print=>'indented');
$currentReport->parsefile($path_to_currentReport);
And this will let you easily compare/copy which ones do or don't exist.
Or alternatively (based on your XML sample so far):
#!/usr/bin/env perl
use strict;
use warnings 'all';
use Data::Dumper;
use XML::Twig;
my $current = XML::Twig -> new ( ) -> parsefile ('test1.xml');
my $new = XML::Twig -> new ( ) -> parsefile ( 'test2.xml');
my $cur_builds = $current -> root -> get_xpath('./builds',0);
foreach my $xcr ( $new -> findnodes('//xcr') ) {
my $id = $xcr -> att('id');
if ( not $current -> findnodes("//xcr[\@id=\"$id\"]") ) {
print "$id not in current, copying\n";
my $copy = $xcr -> copy;
$copy -> paste ( last_child => $cur_builds );
}
}
$current -> set_pretty_print('indented_a');
$current -> print;
回答2:
You should probably move the node (I can't remember what happens when you try to insert an element that's already part of a tree). So write $newXCRmo->move( first_child( $currentBuilds)) and see if this improves the situation.
I don't have much time to look at your code, so there may be other problems with it.
回答3:
You have your comparison loop "inside out"
In addition, the test $count == $numberOfxcr will never succeed because the loop foreach my $newXCRmod (@newXCRarray) will terminate before that is true
Here's an improved version of your code that uses XPath expressions as well as any from List::Util to make the loops more concise
use strict;
use warnings 'all';
use XML::Twig;
use List::Util 'any';
my ( $path_to_curr_report, $path_to_new_report ) = qw/ current.xml new.xml /;
my $out_file = 'fbCI_report.xml';
my $curr_report = XML::Twig->new->parsefile($path_to_curr_report);
my $new_report = XML::Twig->new->parsefile($path_to_new_report);
my ($curr_builds) = $curr_report->findnodes('/project/builds');
for my $new_xcr_mod ( $new_report->findnodes('/project/builds/xcr') ) {
my $new_id = $new_xcr_mod->att('id');
next if any { $new_id eq $_->att('id') } $curr_report->findnodes('/project/builds/xcr');
print qq{XCR with ID "$new_id" does not exist in current report. Adding it.\n};
$new_xcr_mod->copy->paste( last_child => $curr_builds );
}
{
$curr_report->set_pretty_print('indented');
open my $fh, '>', $out_file or die "Can't open $out_file for writing: $!";
$curr_report->print($fh);
close $fh;
}
output
XCR with ID "10867" does not exist in current report. Adding it.
<project>
<builds>
<xcr buildable="false" id="13367">
<artifact name="rb"/>
<artifact name="syca"/>
</xcr>
<xcr buildable="false" id="13826">
<artifact name="dcs"/>
</xcr>
<xcr buildable="true" id="10867">
<artifact name="smth"/>
<artifact name="top"/>
<artifact name="tree"/>
</xcr>
</builds>
</project>
来源：https://stackoverflow.com/questions/38503943/perl-inserting-an-xmltwig-node-with-xmltwig