XML::Writer

[mirod]

Item Description: A CGI.pm-like module to write XML

Review Synopsis: Robust and convenient, recommended over print

Description

XML::Writer generates XML using an interface similar to CGI.pm. It allows various checks to be performed on the document and takes care of special caracter encoding.

Why use XML::Writer?

• you are generating XML documents "from scratch"
• you are used to CGI.pm
• XML::Writer is quite mature

Why NOT use XML::Writer?

• another method is more appropriate
• you don't like CGI.pm!

Related modules

XML::ValidWriter and XML::AutoWriter both aim at emulating XML::Writer interface:

• XML::ValidWriter performs some checks on the output document. Notably it checks whether the elements and attributes are declared in the DTD and whether you are closing the appropriate element.
• XML::AutoWriter automatically generates missing start or end tags, based on the DTD.

XML::Generator and XML::Handler::YAWriter are 2 other modules doing XML generation

Personal notes

At the moment XML::Writer seems to be the most mature and efficient module to generate XML. Of course a lot of the transformation modules such as XML::Simple, XML::DOM and XML::Twig can also be used;

Of course plain print's can also be used, but I think that XML::Writer is a lot more convenient and adds some control over the generated XML.

Example

#!/bin/perl -w

 use strict;
 use XML::Writer;
 use IO;

 my $doc = new IO::File(">doc.xml");
 my $writer = new XML::Writer(OUTPUT => $doc);

 $writer->startTag("doc", class => "simple");           # tag + att
  $writer->dataElement( 'title', "Simple XML Document");# text elt
  $writer->startTag( "section");
   $writer->dataElement( 'title', "Introduction",      
                         no => 1, type => "intro");
   $writer->startTag( "para");
    $writer->characters( "a text with");
    $writer->dataElement( 'bold', "bold");
    $writer->characters( " words.");
   $writer->endTag( "para");
  $writer->endTag();                        # close section      
 $writer->endTag();                         # close doc
 $writer->end();                            # check that the doc
                                            # has only one element
 $doc->close(); # fixed (was $output->close(); ) as suggested by the p
+ost below

[Missing Words]

Nice review of this module. However, when I went to compile your example code I found a small error.

I believe the last line should read:

 $doc->close();

With this change the code compiled fine, and produced the expected output. Regardless of the small error, good review--short and to the point.

[mark838]

When I try using xml::writer, part of my xml doc gets written then the program just hangs, I have tried flushing the buffer. This seems to work in allowing my script to write more data to the xml file. Even though it goes further it still hangs.

[Anonymous Monk]

Good review, and very helpful. One question though. Rather than writing to a file is it possible to simply write to a variable. I've been trying to determine how to do this, and I've had no luck. Thanks

[Anonymous Monk]

I don't have the answer to your specific question however you might take a look at XML::API which does create/return strings of xml.

[Devanchya]

This requires IO::String, but this is one method to put the value of the output into a string: my $xml; my $output = IO::String->new($xml); my $w = new XML::Writer(OUTPUT => $output, ... etc

[metaperl]

XML::Writer::Nest was developed to address the non-language-enforced indentation and tag-closing that you had to do above. here's a pdf to a talk I did explaining how to improve XML::Writer.

[Anonymous Monk]

I want to edit an existing tag,delete a tag,add a tag on an existing XML file,which module is suitable for this?

[Anonymous Monk]

how do we code to obtain the xml tag in below format

<Title lang="pt-BR">Caçadores de Fantasmas</Title>
<Title lang="en-US">Caçadores de Fantasmas - T04-Ep07</Title>

[arunapad]

The above was good for reference .. i had to generate XML in the following format: <games> <game name="chess" players="3" \> <games> ... the <game > tag doesnt have an end tag </game> .. how can i do this using XML writer ??? it would be helpful if u could reply

[mirod]

I can try being helpful, but without your code, it is not that easy...

That said, are you sure the game tag is not <game name="chess" players="3" /> (with a slash instead of a backslash)? In that case it doesn't need a closing tag. The / before the closing angle bracket means that the tag is empty and should be treated as both an opening and a closing tag. As far as an XML parser is concerned <game name="chess" players="3" /> is equivalent to <game name="chess" players="3"></game>, so the XML you are generating should be OK (did you try checking it with an XML parser?).

[Anonymous Monk]

We could use this:


$writer->emptyTag('game', 'name' => 'chess', 'players' => '3');