HttpCallout resulting Html response instead of JSON

Question

I am trying to make a httpcallout to "https://www.carrierlookup.com". When I tried it with browser's apex rest client extension it returned correct response :

{"Response":{"creditBalance":"985","number":"2067998555","carrier_type":"mobile","carrier":"verizon"}}

but when I tried using apex code and debug response using res.getBody(),it showed html response:

<table border="0" cellpadding="4" cellspacing="0">
<thead>
<tr>
<th>Response</th></tr>
</thead>
<tbody>
<tr>
<td Response='Array'></td><td>Array</td></tr>
</tbody>
</table>

I have used below code for callout :

HttpRequest req = new HttpRequest();
req.setEndpoint(endUrl );
req.setMethod('GET');
req.setHeader('Content-Type', 'text/plain');
req.setTimeout(120000);

Http http = new Http();

HttpResponse res = http.send(req);

Can anyone suggest why it is showing this type of response and How can I get the correct result ?

Answer 1

Your request's Accept header is probably going out with the value of */* indicating that you can accept any type of response.

This Content-Type header tells the remote endpoint that you're sending them a json request body - it does not indicate anything about the expected response body.

req.setHeader('Content-Type', 'application/json');

Try specifying that the only type of acceptable response is an application/json response.

req.setHeader('Accept', 'application/json');

Relevant W3.org docs: HTTP/1.1: Header Field Definitions

Answer 2

Try changing the Content Type Header to

req.setHeader('Content-Type', 'application/json');

----Edit----

So I signed up to their service to see if I could figure it out...although it's no documented anywhere, try adding .json to the end of the endpoint. When I do that, it works for me...

e.g.

req.setEndpoint('http://www.carrierlookup.com/index.php/api/balance?key=[myapikey].json');