[Catalyst] Generating a large XML document (KML file) from a database

[Robert Rothenberg]

Thanks. I guessed that was something I needed to do.

One note: when initializing a new XML::Writer object, you can pass $c->res
as the OUTPUT, and XML::Writer will do the right thing, apparently, since it
has a print method.

Also, sending an empty string to body

  $c->res->body("")

is enough.



On 26/11/12 17:54 Francisco Obispo wrote:
> Ok, Now that I'm on my computer, I can write a decent response:
> 
> I had a similar problem with generating a fairly large CSV file.
> 
> you don't want to store this in a stash entry because it can get very large, and 
> even it you were using a temp file to write the data to, the user
> would have to wait until the file is fully written and then
> transferred, which could translate to unresponsiveness.
> 
> I decided to use catalyst ->write() method to output directly
> to the socket, and generate the CSV on the fly.
> 
> On your example, you could use XML::Writer which allows you to 
> generate XML on the fly via:
> 
>   $c->write( $writer->startTag('hello',(attribute=>'value')) );
>   $c->write( $writer->characters('World!') );
>   $c->write( $writer->endTag()) ;
> 
> 
> Will generate to the output buffer:
> 
>   <hello attribute='value'>World!</hello>
> 
> You will need to generate a header with the right content type before you
> start sending out stuff to your output buffer:
> 
>  $c->response->content_type('text/comma-separated-values');
> 
>  $c->res->header( 'Content-Disposition',
>                      qq[attachment; filename=download.csv] );
> 
> 
> This is how I generated mine for the CSV, you would have to fill the 
> right content_type: application/xxx?
> 
> And the name of the file in the Content-Disposition section.
> 
> Notice that you will not provide a Content-Length header, so the
> client will not know how much data you will be sending until its 
> done.
> 
> And catalyst won't know that you actually sent anything so to avoid
> Catalyst rendering the template, just set the body to something, in
> my case I did:
> 
>     $c->response->body(qq{\n});
> 
> I know there are some methods to tell Catalyst to end instead
> of generating the template, but I couldn't get them to work properly.
> 
> 
> Regards
> 
> 
> Francisco Obispo 
> Director of Applications and Services - ISC
> email: fobispo at isc.org
> Phone: +1 650 423 1374 || INOC-DBA *3557* NOC
> PGP KeyID = B38DB1BE
> 
> On Nov 26, 2012, at 8:58 AM, Robert Rothenberg <robrwo at gmail.com> wrote:
> 
>> I need to output a large XML file (actually, a KML file of points) from a
>> database.
>>
>> I can't find any documentation for Catalyst::View::XML::Generator, or even
>> decent documentation for XML::Generator, on how to do this.
>>
>> It would appear to expect me to put the entire structure in the stash, which
>> I don't want to do, as it could contain thousands of points.
>>
>> Ideally I would pass an iterator function and it would do the rest.
>>
>>
>>
>>
>>
>>
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> 
> 
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