Cannot upload a file in blob in sharefile - salesforce

Question

I am trying to upload a file in Citrix ShareFile via REST API. There are four requests
Get the access_token
Get the folder URI's to decide n which I am going to upload the file.
Get chunk Uri
Upload the file in that chunk Uri
The first three steps work perfectly. When I am trying to POST a request for the no 4. part,
it is creating a file in sharefile but with size of 0.
I have tried that with POSTMAN, and with form-data and the selection of a file, it is working fine. The file is uploaded in sharefile.
The problem arises when I am trying to upload blob data.
I am calling this methods from Salesforce Platform and in Salesforce, I cannot get the physical file in a physical location. I have blob file data stored in salesforce database.
The below part works well.
String fileName_m = 'a12.pdf';
// Get Authentication Token
HttpRequest req = new HttpRequest();
req.setEndpoint('https://{server}.sf-api.com/oauth/token?grant_type=password&client_id={client_id}&client_secret={secret}&username={user_name}&password={password}!');
req.setMethod('GET');
Http http = new Http();
HttpResponse response = http.send(req);
System.Debug(response.getBody());
Map<String, Object> results = (Map<String, Object>)JSON.deserializeUntyped(response.getBody());
String token = '';
String refreshtoken = '';
if(response.getStatusCode() == 200){
token = (String)results.get('access_token');
refreshtoken = (String)results.get('refresh_token');
}
system.debug('token=' + token);
// Get Folder ID
HttpRequest req1 = new HttpRequest();
req1.setEndpoint('https://{server}.sf-api.com/sf/v3/Items?$expand=Children');
req1.setMethod('GET');
req1.setHeader('Authorization','Bearer ' + token);
Http http1 = new Http();
HttpResponse response1 = http1.send(req1);
System.Debug(response1.getBody());
Map<String, Object> results1 = (Map<String, Object>)JSON.deserializeUntyped(response1.getBody());
String url = '';
if(response1.getStatusCode() == 200){
url = (String)results1.get('url');
}
System.Debug('Folder Url ' + url);
// Get Chunk URI
HttpRequest req2 = new HttpRequest();
String endPoint = url + '/Upload2';
req2.setEndpoint(endPoint);
req2.setMethod('POST');
req2.setHeader('Authorization','Bearer ' + token);
req2.setHeader('Content-Type', 'application/x-www-form-urlencoded');
String payload1 = 'FileName='+fileName_m;
req2.setBody(payload1);
Http http2 = new Http();
HttpResponse response2 = http2.send(req2);
Map<String, Object> results2 = (Map<String, Object>)JSON.deserializeUntyped(response2.getBody());
String ChunkUri = '';
if(response2.getStatusCode() == 200){
ChunkUri = (String)results2.get('ChunkUri');
}
System.Debug('ChunkUri' + ChunkUri);
But, when I am trying to upload blob file data in sharefile, the API responds with a 200 status code. In sharefile, the file is created, but the size of the file is 0.
// Problem is here, it is not working
// Upload File
Attachment att = [SELECT Id, Body, Name, ContentType FROM Attachment WHERE Id='00P3p00001XNLOHEA5'];
String body = EncodingUtil.base64Encode(att.body);
List<Attachment> cvList = [SELECT Id, Body, Name, ContentType FROM Attachment WHERE Id='00P3p00001XNLOHEA5'];
String attachmentBody = EncodingUtil.base64Encode(cvList[0].Body);
Blob pdfBlob = EncodingUtil.base64Decode(attachmentBody);
system.debug('pdfBlob' + pdfBlob);
HttpRequest req3 = new HttpRequest();
req3.setEndpoint(ChunkUri);
req3.setMethod('POST');
req3.setHeader('Authorization','Bearer ' + token);
req3.setHeader('Content-Length', String.valueOf(attachmentBody.length()));
req3.setHeader('Content-Encoding', 'UTF-8');
req3.setHeader('Content-type', 'application/pdf');
req3.setHeader('Connection', 'keep-alive');
req3.setBodyAsBlob(pdfBlob);
Http http3 = new Http();
HttpResponse response3 = http3.send(req3);
System.Debug(response3.getBody());
How to solve the issue?