Currently shopify support CSV imports, either through an application or in the admin. xml file uploads, would not be supported.
When importing products, Shopify does all the work for you. Instead of creating each product one at-a-time, Shopify extracts data from CSV file and turns them into products in your Shopify store.
1) If you are creating your CSV file from scratch, click the Download a sample CSV template to see an example of the format required link.
2) Make sure to match the order on that CSV file to yours so that it can be successfully uploaded to Shopify.
3) Save your CSV file somewhere on your computer.
4) Back in your shop admin, click on the Import products by CSV link.
5)Click the Choose File button.
6) Locate your CSV file, then click the Open button and on the “Import product by CSV” page, click the Upload file button.
If your CSV file was successfully uploaded you should recieve an email from Shopify to the email account used to setup your Shopify store, saying that the process was successful.