I'm trying to POST some JSON data to my Perl script, but the JSON module seems to be unable to cope with this string:

[{"":"#","jednostka":"","login":"SA"}]

I used encodeURIComponent() in JavaScript, so my string actually looks like this:

[{%22%22:%22#%22,%22jednostka%22:%22%22,%22login%22:%22SA%22}]

Error log:

JSON::PP::decode_error('unexpected end of string while parsing JSON string') called at C:\strawberry\perl\lib/JSON/PP.pm line 837
|   JSON::PP::string() called at C:\strawberry\perl\lib/JSON/PP.pm line 960
|   JSON::PP::object() called at C:\strawberry\perl\lib/JSON/PP.pm line 724
|   JSON::PP::value() called at C:\strawberry\perl\lib/JSON/PP.pm line 907
|   JSON::PP::array() called at C:\strawberry\perl\lib/JSON/PP.pm line 725
|   JSON::PP::value() called at C:\strawberry\perl\lib/JSON/PP.pm line 688
|   JSON::PP::PP_decode_json('JSON::PP=HASH(0xd0c2534)', '[{%22%22:%22#%22,%22jednostka%22:%22%22,%22login%22:%22SA%22}]', 0) called at C:\strawberry\perl\lib/JSON/PP.pm line 148

I'm trying to POST some JSON data to my Perl script, but the JSON module seems to be unable to cope with this string:

[{"":"#","jednostka":"","login":"SA"}]

I used encodeURIComponent() in JavaScript, so my string actually looks like this:

[{%22%22:%22#%22,%22jednostka%22:%22%22,%22login%22:%22SA%22}]

Error log:

JSON::PP::decode_error('unexpected end of string while parsing JSON string') called at C:\strawberry\perl\lib/JSON/PP.pm line 837
|   JSON::PP::string() called at C:\strawberry\perl\lib/JSON/PP.pm line 960
|   JSON::PP::object() called at C:\strawberry\perl\lib/JSON/PP.pm line 724
|   JSON::PP::value() called at C:\strawberry\perl\lib/JSON/PP.pm line 907
|   JSON::PP::array() called at C:\strawberry\perl\lib/JSON/PP.pm line 725
|   JSON::PP::value() called at C:\strawberry\perl\lib/JSON/PP.pm line 688
|   JSON::PP::PP_decode_json('JSON::PP=HASH(0xd0c2534)', '[{%22%22:%22#%22,%22jednostka%22:%22%22,%22login%22:%22SA%22}]', 0) called at C:\strawberry\perl\lib/JSON/PP.pm line 148

• javascript
• json
• perl
• post

• How are you parsing the JSON? Have you tried JSON.parse('[{"":"#","jednostka":"","login":"SA"}]') ? – Krishnakumar_Muraleedharan Commented Jul 12, 2016 at 5:58
• I'm not sure why you need the encodeURIComponent(). doesn't it work without it? and shouldn't you do decode on the other side? – Ronen Ness Commented Jul 12, 2016 at 6:14
• I can't reproduce the problem, you need to provide an minimal reproducible example – Quentin Commented Jul 12, 2016 at 6:54

3 Answers 3

Do you realise that you ned to escape the data only for GET requests? That's why the function is called encodeURIComponent, because the resulting string is for use within a URL. In POST requests the data is passed in the message body, not in the URL

I see that you're using the JSON::PP module, which works fine with the simple JSON string that you show. Here's an example program that shows the resulting data structure dumped using Data::Dump

Acccording to the error log you're encoding the JSON data when you shouldn't be. If I replace the JSON data below with encodeURIComponent then I get the error message

unexpected end of string while parsing JSON string, at character offset 3 (before "22%22:%22#%22,%22jed...")

which is as you described, and what the error log confirms

use strict;
use warnings 'all';

use JSON::PP;
use Data::Dump;

my $json = '[{"":"#","jednostka":"","login":"SA"}]';

my $data = JSON::PP::decode_json($json);

dd $data;

output

[{ "" => "#", "jednostka" => "", "login" => "SA" }]

Another way to get the "unexpected end of string while parsing JSON string" from Perl's JSON::decode_json() function, is if your JSON file contains trailing mas, like this:

{"widget": {
    "debug": "on",
    "window": {
        "title": "Sample Konfabulator Widget",
        "name": "main_window",
        "width": 500,
        "height": 500,
    }  }}

The JSON specification does not allow a trailing ma (this is unrelated to URI-encoding, btw). You should be able to catch such JSON format violations using JSON::Parse::valid_json().

It looks like you're decoding it in Perl, but attempting to decode an empty variable name. Give the first variable a name.