API POST not working on executeAnonymous BUT IS working on Postman

Question

I'm having trouble getting a POST request to go trough using the Execute Anonymous window. The endpoint is exactly the same in my postman and it goes trough with no issues, but keeps returning a 400 when sent from Salesforce.

I HAVE added 'https://graph.facebook.com' to my Remote Site Settings

And here is the code on the Execute Anonymous..

HttpRequest req = new HttpRequest();
req.setMethod('POST');                                    
//Seting HttpRequest Method
req.setHeader('content-type', 'application/json');       
//Seting HttpRequest header properties
req.setHeader('Content-Length', '2000');
req.setEndpoint('https://graph.facebook.com/v15.0/xxxxxxxxx/messages?recipient={id:xxxxxxxxxxxx}&message={text:"HELLO, HOW ARE YOU"}&messaging_type=MESSAGE_TAG&tag=ACCOUNT_UPDATE&access_token=xxxxxxxxxxxxxxxxxx');
Http http = new Http();
try{
    HTTPResponse res = http.send(req);                 
    //Executing web service call
    System.debug('STATUS:' + res.getStatus());
    System.debug('STATUS_CODE:' + res.getStatusCode());
}
catch(System.CalloutException e){
    //Exception handling goes here..
    system.debug(e);
}

Which is returning:

But is successful in Postman:

Answer 1

via: https://stackoverflow.com/a/36284027/19789973 I found out it is the whitespace in the text string causing the issue. I Replaced this using '%20' and the POST was successful! For example: text:"random%20text%20here"