Apex Callout HTTP POST with Named Credentials error [closed]

Question

I am constructing something wrong, in the POST request. Please advise.

Step 1: Created Named Credential called Stock_Check_For_Materials

Step 2: Created Apex Controller as below

Continuation con = new Continuation(40);
con.continuationMethod='processResponse';
HttpRequest req = new HttpRequest();
req.setEndpoint('callout:Stock_Check_For_Materials/stockcheck');
req.setMethod('POST');
req.setHeader('Content-Type','application/json');  
req.setBody('customerNumber='+EncodingUtil.urlEncode(cN, 'UTF-8')+'&requireGenericEquivalent='+EncodingUtil.urlEncode(rGE, 'UTF-8')+'&itemNumber='+EncodingUtil.urlEncode(itN, 'UTF-8')+'&orderQuantity='+EncodingUtil.urlEncode(oQ, 'UTF-8'));
this.requestLabel = con.addHttpRequest(req);

Please note that the 'customerNumber', 'requireGenericEquivalent', 'itemNumber' and 'orderQuantity' are the POST body for request and cN,rGE,itN,oQ are the getter and setter variable values coming from the visualforce page to this controller.

Answer 1

You've specified the Content-Type as application/json, but you're using a application/x-www-form-encoded encoding style. You need to make sure they agree with each other.

// These do not agree with each other
req.setHeader('Content-Type','application/json');
req.setBody('customerNumber='+EncodingUtil.urlEncode(cN, 'UTF-8')+'&requireGenericEquivalent='+EncodingUtil.urlEncode(rGE, 'UTF-8')+'&itemNumber='+EncodingUtil.urlEncode(itN, 'UTF-8')+'&orderQuantity='+EncodingUtil.urlEncode(oQ, 'UTF-8'));

Corrected

String jsonBody = JSON.serialize(
new Map<String, String> {
'customerNumber' => cN,
'requireGenericEquivalent' => rGE, 
'itemNumber' => itN,
'orderQuantity' => oQ});
req.setHeader('Content-Type','application/json');
req.setHeader('Content-Length',jsonBody.length()+'');
req.setBody(jsonBody);