[Dancer-users] storing JSON in a db for later use

[Naveed Massjouni]

On Sat, Dec 25, 2010 at 11:49 PM, Puneet Kishor <punk.kish at gmail.com> wrote:
> Actually, I had pursued this problem a while back on this list, received
> helpful suggestions, implemented a solution, and all was working. Except,
> recently (a few days ago) when it stopped working. I can't quite pinpoint
> what caused the program to break, but I am now writing to elicit suggestions
> afresh so I can create a robust solution.
>
> I am deploying all the nice touches that Dancer offers, namely,
>
>        use Dancer::Serializer::Mutable;
>        use Dancer::Plugin::REST;
>        prepare_serializer_for_format;
>
> I have a longish JSON object in the browser that I stringify and send back
> to the server with the help of jQuery. I store this string into a sqlite db.
> The string looks like
>
>
> [{"data":"{"year":"1900","harvest_area":"126800.00", .. (very long string)
>
> At a later time, I retrieve the above value, send it back to the browser
> where it is reconstructed back into a JSON object which can be used. Except,
> ever since I started using the automatic serializer, the darn thing has
> stopped working. The JSON object is not fully reconstructed. The above
> string is received by the browser as
>
> [{"data":"{\"year\":\"1900\",\"harvest_area\":\"126800.00\", .. (very long
> string)
>
> The automatically generated headers received are
>
> Request Header
> --------------
> Accept:application/json, text/javascript, */*; q=0.01
>
> Response Header
> --------------
> Content-Type:text/xml; charset=UTF-8
>
>
> I think it is those escaped double quotes in the response (\"year\") are
> creating trouble for me. The value of the "data" key in the JSON object
> should be another dataset, but comes off as a string instead.
>
> As I said above, this was working when I didn't use the automatic
> serializers (D::S::Mutable and D::P::REST with
> `prepare_serializer_for_format`). I used to retrieve the values from the db,
> transform them with from_json() to a Perl data structure, created a data
> structure to return, convert it to a string with to_json() and send it back
> to the browser.
>
>    $sth = __PACKAGE__->SUPER::db()->prepare(qq{
>        SELECT id, name, data, poly
>        FROM foo
>    });
>    $sth->execute;
>
>    my @str = ();
>    while (my ($id, $name, $data, $poly) = $sth->fetchrow_array) {
>        push @str, {
>            id   => $id,
>            name => $name,
>            data => from_json($data),
>            poly => from_json($poly)
>        }
>    }
>
>    return to_json(\@str);
>
> Now I don't use the from_json() and the to_json() calls. Needless to say, if
> I use those calls, I get an error on the server side that
>
> {"error":"malformed JSON string, neither array, object, number, string or
> atom, at character offset 0 (before \"(end of string)\") at (eval 64) line
> 163.\n"}
>
> and, if I don't use from_json() and to_json(), I get
>
> [{"data":"{\"year\":\"1900\",\"harvest_area\":\"126800.00\", ..
>
> which stops my application on the browser side.
>
> So, I am stuck.
>
> If the above is too confusing, I ask this simple question --
>
> How do I reliably send a stringified JSON object to Dancer (I use the
> canonical json2.js from Crockford's site), store it in a sqlite table,
> retrieve it, have Dancer stringify it, send it back to the browser, and
> reconstruct the original JSON object 100%? I want round-trip browser to db
> back to the browser.
>
> Suggestions?

Return to_json { ... } in your route.
-Naveed

>
>
>
> --
> Puneet Kishor http://punkish.org
> Carbon Model http://carbonmodel.org
> Charter Member, Open Source Geospatial Foundation http://www.osgeo.org
> Science Fellow http://creativecommons.org/about/people/fellows#puneetkishor
> Nelson Institute, UW-Madison http://www.nelson.wisc.edu
> ---------------------------------------------------------------------------
> Assertions are politics; backing up assertions with evidence is science
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