How do I dynamically generate XML?

Question

I actually asked this question in a different form before. I did get a great answer but I thought I needed more clarifications, so I am asking it in its whole form again.

The user would script something like:

$ABC->Command(100, 100);
my $group  = "1";
my $id     = "1";
my $value1 = "Some Process A Happened";
$rep->getParameter($group, $id, $value1);
$ABC->Command(100, 100);
my $group  = "1";
my $id     = "2";
my $value1 = "Some Process B Happened";
$rep->getParameter($group, $id, $value1);
$ABC->Command(100, 100);
my $group  = "2";
my $id     = "1";
my $value1 = "Some Process A Happened";
$rep->getParameter($group, $id, $value1);
$ABC->Command(100, 100);
my $group  = "2";
my $id     = "1";
my $value1 = "Some Process Happened";
$rep->getParameter($group, $id, $value1);
$ABC->Command(100, 100);
my $group  = "3";
my $id     = "1";
my $value1 = "Some Process Happened";
$rep->getParameter($group, $id, $value1);
$ABC->SomeImage($image) $desc = "Some info";
$rep->getImage($image, $desc);
$rep->getResult("Pass")

This would have to generate an XML like:



    Pass
    Executed Successfully
    
        
            Some Value
            Some Value
            Some Value
        
        
            Some Value
            Some Value
            Some Value
        
        
            Some Value
            Some Value
            Some Value
        
    
    
        info
        info
        info

The image values and parameter values will be input at different points of time. But they would have to be collected and placed inside the Images element, similarly for Parameters. What approach should I follow here? Some code samples, please.

edited:

I have something like

$xml = {
    ParameterGroup => [
        {
            ID        => 'Group1',
            Parameter => {
                Key1  => {content => 'Some Value'},
                Key2  => {content => 'Some Value'},
                Key3  => {content => 'Some Value'},
            },
        },
        {
            ID        => 'Group2',
            Parameter => {
                Key1  => {content => 'Some Value'},
                Key2  => {content => 'Some Value'},
                Key3  => {content => 'Some Value'},
            },
        },
    ]
};
print XMLout(
    $xml,
    RootName => 'Parameters',
    KeyAttr  => 'value',
);

as the structure but these are fixed structures. How can I make this dynamic to suit the users' requirement?

Greg Bacon · Accepted Answer

Consider a few small adjustments below to your driver code.

#! /usr/bin/env perl

use warnings;
use strict;

use TestResult;

my $tr = TestResult->new;

$tr->parameter(1, 1, "Some Process A Happened");
$tr->parameter(1, 2, "Some Process B Happened");
$tr->parameter(2, 1, "Some Process A Happened");
$tr->parameter(3, 1, "Some Process Happened");

$tr->image(1, "Some info");

$tr->result("Pass");
$tr->comments("Executed Successfully");

print $tr->as_xml;

The XML output is



  Pass
  Executed Successfully
  
    
      Some Process A Happened
      Some Process B Happened
    
    
      Some Process A Happened
    
    
      Some Process Happened
    
  
  
    Some info

Seeing a dump of the contents of $self->{_xml} may aid your understanding.

{
  'Comments' => { 'content' => 'Executed Successfully' },
  'Parameters' => {
    'ParameterGroup' => {
      'Group1' => {
        'Parameter' => {
          'Key2' => { 'content' => 'Some Process B Happened' },
          'Key1' => { 'content' => 'Some Process A Happened' }
        }
      },
      'Group3' => {
        'Parameter' => {
          'Key1' => { 'content' => 'Some Process Happened' }
        }
      },
      'Group2' => {
        'Parameter' => {
          'Key1' => { 'content' => 'Some Process A Happened' }
        }
      }
    }
  },
  'xmlns' => 'http://test.com/automate',
  'Result' => { 'content' => 'Pass' },
  'xmlns:xsi' => 'http://www.w3.org/2001/XMLSchema-instance',
  'xsi:schemaLocation' => 'http://test.com/automate',
  'Images' => {
    'ImageTag1' => { 'content' => 'Some info' }
  }
}

The TestResult module that gets you there is below. Be sure to put it in a file named TestResult.pm somewhere in the module search path. It begins with familiar boilerplate.

package TestResult;

use strict;
use warnings;

use XML::Simple;

At compile time, we set up a subclass of XML::Simple specific to your desired XML format that will output elements in the appropriate order.

BEGIN {
  @__PACKAGE__::XML::ISA = qw/ XML::Simple /;

  my %order = (
    TestResult => [qw/
      xmlns xmlns:xsi xsi:schemaLocation
      Result Comments Parameters Images
    /],
  );

  *__PACKAGE__::XML::sorted_keys = sub {
    my($self,$name,$h) = @_;
    return @{ $order{$name} } if $order{$name};
    sort keys %$h;
  };
}

Each instance will carry the contents of the output document. The hardcoded key-value pairs become attributes of the TestResult element.

sub new {
  my($class) = @_;
  my $self = {
    _xml => {
      "xmlns"              => "http://test.com/automate",
      "xmlns:xsi"          => "http://www.w3.org/2001/XMLSchema-instance",
      "xsi:schemaLocation" => "http://test.com/automate",
    },
  };

  bless $self => $class;
}

The implementations of comments and result are simple because the XML they produce is simple. The methods stuff bits in the appropriate slots with no surprises.

sub comments {
  my($self,$comments) = @_;
  $self->{_xml}{Comments} = { content => $comments };
}

sub result {
  my($self,$result) = @_;
  $self->{_xml}{Result} = { content => $result };
}

We have to be careful with image and parameter because they contain multiple children. Blindly overwriting $self->{_xml}{Images} or $self->{_xml}{Parameter} would clobber any content that had already been accumulated, so instead we add new elements incrementally.

sub image {
  my($self,$image,$desc) = @_;

  my $imageid = "ImageTag" . $image;
  $self->{_xml}{Images}{$imageid} = { content => $desc };
}

sub parameter {
  my($self,$group,$key,$value) = @_;

  my $groupid = "Group" . $group;
  my $keyid   = "Key"   . $key;

  $self->{_xml}{Parameters}{ParameterGroup}{$groupid}{Parameter}{$keyid} =
    { content => $value };
}

Finally, we encode the XML using TestResult::XML. The GroupTags parameter declares nesting relationships, e.g., contains . (At first, I tried giving similar treatment to the relationships between and and between and , but the XML output differed from what you want.) The KeyAttr parameter tells XML::Simple to use Perl hash-keys as XML attributes. The + prefixes will make for nicer results if you ever use XMLin to read TestResults generated by other tools.

sub as_xml {
  my($self) = @_;

  my $serialize = __PACKAGE__::XML->new;

  $serialize->XMLout(
    $self->{_xml},
    GroupTags => {
      Images => "Image",
    },
    KeyAttr => {
      ParameterGroup => "+ID",
      Parameter      => "+key",
      Image          => "+key",
    },
    RootName => "TestResult",
    XMLDecl => '',
  );
}

Return a true value to indicate that the module loaded successfully.

1;

How do I dynamically generate XML?

Answers (2)

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