Setting json string in http requests in Perl

Question

Following Perl code generates an error printed below:

use strict;
use Data::Dumper;
use LWP::UserAgent;
use JSON;

my $token = 'my token';
my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new(PUT => "endpoint");
$req->header( 'Authorization' => "Bearer $token" );
$req->content_type('application/json');
$req->content('{"text":"whiteboard"}');
 
my $res = $ua->request($req);     
if ($res->is_success) {
    my $content = $res->decoded_content;
    my $fromjson = from_json($content);
    print Dumper $fromjson->{'results'}; 
}
else {
    print $res->status_line, "\n";
    print $res->content, "\n";
}

Error:

 {"detail":[{"loc":["body"],"msg":"str type expected","type":"type_error.str"}]}

However if I write the same code in Python, it works:

import requests
import os
import json

url = 'endpoint'
token='my token'

headers = {
            "Authorization": "Bearer "+token[:-1],
            "Content-type" : "application/json"
            }
res=requests.put(url, json='{"text":"whiteboard"}', headers=headers)
#res=requests.put(url, json='test string', headers=headers) # this also works
print('Response Content:\n',res)

What am I missing in the Perl code?

The Authorization token in the Python version is "my toke". In the perl version it's "my token". I don't think this is the root cause, but it is a difference. — Michael Ruth
– Michael Ruth, Commented Oct 11, 2023 at 23:27
Try printing $req->as_string to see what's actually being sent. — Schwern
– Schwern, Commented Oct 11, 2023 at 23:51

Schwern · Accepted Answer · 2023-10-12 00:07:00Z

2

I believe Perl is sending the JSON object {"text":"whiteboard"}. Python is sending the JSON string "{\"text\":\"whiteboard\"}".

What the error is saying is the endpoint expects the body to be a JSON string, not a JSON object, so only the Python code works.

What you probably want is something like $req->content(q["a string"]). It's safer to encode it with a JSON encoder like in ikegami's answer.

In your Perl code, $req->content('{"text":"whiteboard"}') just sends the string {"text":"whiteboard"} as the body.

In your Python code, res=requests.put(url, json='{"text":"whiteboard"}', headers=headers) serializes the string {"text":"whiteboard"} into JSON. The body is a single JSON string "{\"text\":\"whiteboard\"}".

From the docs....

json – (optional) A JSON serializable Python object to send in the body of the Request.

If you wanted to send a JSON object you'd pass it a Python dict.

res=requests.put(url, json={"text":"whiteboard"}, headers=headers)

This should result in the same error.

edited Oct 12, 2023 at 0:07

answered Oct 12, 2023 at 0:01

Schwern

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1 Comment

Jean Over a year ago

$req->content(q["a string"]). This works! Thanks!

ikegami · Accepted Answer · 2023-10-12 18:04:21Z

2

The Perl equivalent would be

use Cpanel::JSON::XS qw( );

my $serializer = Cpanel::JSON::XS->new->utf8->allow_nonref;

$req->content( $serializer->encode( '{"text":"whiteboard"}' ) );

According to the docs (search for json=),

requests.put( url, json=payload )

is equivalent to

import json

headers={ 'Content-Type': 'application/json' }
requests.put( url, data=json.dumps( payload ), headers=headers )

In other words, the value provided to json is encoded using JSON. This means the following is the body of the message sent by the Python script:

"{\"text\":\"whiteboard\"}"

edited Oct 12, 2023 at 18:04

answered Oct 12, 2023 at 0:04

ikegami

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2 Comments

Jean Over a year ago

It is giving following error if I try your solution. hash- or arrayref expected (not a simple scalar, use allow_nonref to allow this) at

ikegami Over a year ago

So use the allow_nonref option.

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