Uploading File to AEM DAM

I am working on a Project to upload files to AEM DAM through Java API. So was going through this tutorial to upload files in DAM.

"Adobe Experience Manager Help | Uploading files to Adobe Experience Manager DAM using AssetManager API "

But I am not able to get this code check as I am getting “Null Pointer Exception” @ ResourceResolver resourceResolver = resolverFactory.getAdministrativeResourceResolver(null);

Pasting the code as well which I am writing, just to let you know AEM is running on a different server and I am trying to connect to that server from my local, Idea is to deploy it as a Rest API in a different server from AEM.

Thanks in advance any help will be appreciated.

@Reference

       private static ResourceResolverFactory resolverFactory;

       public static void main(String[] args) {

//InputStream is =null;

try{

File initialFile = new File("C:/Users/502719757/Desktop/DOC0928611r8VCT_750HD_RevDis.pdf");

InputStream targetStream = new FileInputStream(initialFile);

String fileName = "DOC0928611r8VCT_750HD_RevDis.pdf";

String path = "http://uswaupmcvms01l.am.health.ge.com:8001/content/dam/travel";

String mimetype= null;

writeToClientLib(targetStream,fileName,path,mimetype);

}

catch(Exception e){

}

       }

       //

       private static String writeToClientLib(InputStream is, String fileName, String path, String mimetype)

       {

       try

       {

//Inject a ResourceResolver

ResourceResolver resourceResolver = resolverFactory.getAdministrativeResourceResolver(null);

//Use AssetManager to place the file into the AEM DAM

com.day.cq.dam.api.AssetManager assetMgr = resourceResolver.adaptTo(com.day.cq.dam.api.AssetManager.class);

String newFile = path+fileName ;

assetMgr.createAsset(newFile, is, mimetype, true);

// Return the path to the document that was stored in CRX.

return newFile;

       }

       catch(Exception e)

       {

e.printStackTrace();

System.out.println(e);

       }

       return null;

       }