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yet another xml generator Martin Busik 03-17-2008
Posted by Martin Busik on March 17, 2008, 9:38 pm
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 Hello,
there are some modules aimed to make the xml generation easy - =

XML::Generator,
XML::Writer and XML:Writer::Simple, for example.

For my needs, these are to "verbose" and there is too much code necessar=
y
to express the structure of the resulting xml. So I wrote a piece of cod=
e
which uses a bit more declarative approach. If somebody finds it useful,=

I'd put it on CPAN - or submit it to an existing module.

Let's look at this code:

$str =3D element "outer", content {
        element "inner" =3D> content {
                attribute id =3D> 1;
                element "abc", undef;
                opt_element "def", $value;
                element "ghi", "bb & cc";
        }
}

provided that $value contains "dummy", $str contains the following resul=
t:

<outer>
<inner id=3D'1'>
<abc/>
<def>dummy</def>
<ghi>bb &amp; cc</ghi>
</inner>
</outer>

provided that $value is undef or "", $str would contain:

<outer>
<inner id=3D'1'>
<abc/>
<ghi>bb &amp; cc</ghi>
</inner>
</outer>

Another example:

$str =3D opt_element "abc", content {
        opt_element "def", $value
}

provided $value is undef or "", as result, $str would contain "".
If $value would be "zzz", $str would contain:

<abc>
<def>zzz</dev>
</abc>

Any comments?

Cheers,
Martin

Posted by Darin McBride on March 18, 2008, 3:54 pm
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 Martin Busik wrote:

> Hello,
> there are some modules aimed to make the xml generation easy -
> XML::Generator,
> XML::Writer and XML:Writer::Simple, for example.
>
> For my needs, these are to "verbose" and there is too much code necessary
> to express the structure of the resulting xml. So I wrote a piece of code
> which uses a bit more declarative approach. If somebody finds it useful,
> I'd put it on CPAN - or submit it to an existing module.

This looks really interesting. What would hold me back, personally, is
integrating it into other methods. For example, I usually have a stock, or
template, XML file, and then use XML::Twig to read that, add/remove/modify
what I need to, and write it out (to a file, to stdout for apache to send,
whatever). If I could do something like:

$twig->insert_decl('after',
twig_element "out", content {
#...
});

that'd be really cool - a huge time-saver on some of my projects.

> Let's look at this code:
>
> $str = element "outer", content {
> element "inner" => content {
> attribute id => 1;
> element "abc", undef;
> opt_element "def", $value;
> element "ghi", "bb & cc";
> }
> }
>
> provided that $value contains "dummy", $str contains the following result:
>
> <outer>
> <inner id='1'>
> <abc/>
> <def>dummy</def>
> <ghi>bb &amp; cc</ghi>
> </inner>
> </outer>
>
> provided that $value is undef or "", $str would contain:

I would suggest that $value as undef should do this, if it's "", then it
should insert the empty element. In fact, I'd merge your element and
opt_element together:

element "abc"; #creates the "abc" element, empty
element "abc", ""; # same thing
element "abc", undef; # no-op

Also, how do I put an element in the middle of the text of another element?
Does this work?

element "p", "a paragraph with some ", element("b", "bold"), " text";

I'm guessing not. If my guess is correct, I'd suggest at least adding that
as a limitation in the POD.

Posted by John Bokma on March 19, 2008, 7:16 pm
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> if all of the above variables contain either undef or "", no output is
> generated
> at all. IMO this makes it more readable.

I recommend to make this a setting for each, i.e.

undef -> generate empty element, or no-op, or exception
"" -> generate empty element, or no-op, or exception

--
John

Arachnids near Coyolillo - part 1
http://johnbokma.com/mexit/2006/05/04/arachnids-coyolillo-1.html

Posted by mirod on March 20, 2008, 6:40 am
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> there are some modules aimed to make the xml generation easy - =A0
> XML::Generator, XML::Writer and XML:Writer::Simple, for example.
>
> For my needs, these are to "verbose" and there is too much code necessary
> to express the structure of the resulting xml. So I wrote a piece of code
> which uses a bit more declarative approach. If somebody finds it useful,
> I'd put it on CPAN - or submit it to an existing module.
>
> Let's look at this code:
>
> $str =3D element "outer", content {
> =A0 =A0 =A0 =A0 element "inner" =3D> content {
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 attribute id =3D> 1;
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 element "abc", undef;
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 opt_element "def", $value;
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 element "ghi", "bb & cc";
> =A0 =A0 =A0 =A0 }
>
> }
>
> provided that $value contains "dummy", $str contains the following result:=

>
> <outer>
> =A0 <inner id=3D'1'>
> =A0 =A0 <abc/>
> =A0 =A0 <def>dummy</def>
> =A0 =A0 <ghi>bb &amp; cc</ghi>
> =A0 </inner>
> </outer>
>
> provided that $value is undef or "", $str would contain:
>
> <outer>
> =A0 <inner id=3D'1'>
> =A0 =A0 <abc/>
> =A0 =A0 <ghi>bb &amp; cc</ghi>
> =A0 </inner>
> </outer>
>
> Another example:
>
> $str =3D opt_element "abc", content {
> =A0 =A0 =A0 =A0 opt_element "def", $value
>
> }
>
> provided $value is undef or "", as result, $str would contain "".
> If $value would be "zzz", $str would contain:
>
> <abc>
> =A0 <def>zzz</dev>
> </abc>
>

Have you looked at HTML::Element? It lets you create elements from a
Perl structure:

http://search.cpan.org/~petek/HTML-Tree-3.23/lib/HTML/Element.pm#@elements_=
=3D_HTML::Element-%3Enew_from_lol(ARRAYREFS)

Your first example would be:

my $elt =3D HTML::Element->new_from_lol(
[ outer =3D>
[ inner =3D> { id =3D> 1 },
[ 'abc' ],
$value && [ def =3D> $value ],
[ ghi =3D> 'bb & cc' ],
]
]);

print $elt->as_XML;

XML::TreeBuilder is based on HTML::Element and can be used to process
XML.

You could add a function opt_elt to avoid repeating the $value, and
you would be quite close to your original syntax, while getting the
rest of the XML::TreeBuilder fetures for free.

--
mirod



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