Download BLOBs from Azure

Question

What is the best way and the best practice to download large BLOBs from the Azure storage?

• I want to use Shared Access Signature or Shared Access Policy to make a local copy of BLOBs.

• The estimated BLOB size is 500 MB to 1 GB

• Internet connections vary from 250Kb to 4Mb

Answer 1

In case of REST API use the HTTP request header

In case of Storage Client Library for .NET use DownloadRangeToStream

Answer 2

The best way depends upon your situation. Is there a specific reason preventing you from not to doing something along the lines of the following (Java code)? I have seen examples like this, but would be interested in learning why you think it might not work for you.

    public class SASread 
{
    public static void main(String[] args) throws URISyntaxException, FileNotFoundException, StorageException, IOException 
    {                       
    URI baseuri = new URI("http://greengrass.blob.core.windows.net");
    CloudBlobClient blobclient = new CloudBlobClient(baseuri);
    MyDownloadBlob("container1",
           "sr=c&sv=2012-02-12&sig=ADsFalIpE1XkaneQpWwtpM3AhY%2BAwiUtbbo1ANbIoJA%3D&si=r",
           blobclient);         
    }

    public static void MyDownloadBlob(String containerName, String containerSAS, CloudBlobClient blobClient) throws URISyntaxException, StorageException, FileNotFoundException, IOException
    {   
    String blobName = "image3.jpg";  
    String localFileName = "c:\\myoutputimages\\image3.jpg";  
    URI uri = new URI(blobClient.getEndpoint().toString() + "/" +
                      containerName + "/" + 
                      blobName + 
                      "?" + 
                      containerSAS);   
    CloudBlockBlob sasBlob = new CloudBlockBlob(uri, blobClient);   
    File fileTarget = new File(localFileName); 
    sasBlob.download(new FileOutputStream(fileTarget));
    System.out.println("The blob at:\n"  + uri + "\nwas downloaded from the cloud to local file:\n" + localFileName);   
    }
}