How to open blobs on browser without downloading through java service?

Question

I am creating an application where I need to view blobs in browser rather than downloading them. Currently, links of blobs having token downloads the corresponding blob.

I got some reference here to view the blobs in browser : https://github.com/Azure-Samples/storage-blob-java-getting-started/blob/master/src/BlobBasics.java (See from line number 141)

Here is my code to create token :

@Test
    public String testBlobSaS(CloudBlob blob, CloudBlobContainer container) throws InvalidKeyException,
            IllegalArgumentException, StorageException, URISyntaxException, InterruptedException {
        SharedAccessBlobPolicy sp = createSharedAccessBlobPolicy(
                EnumSet.of(SharedAccessBlobPermissions.READ, SharedAccessBlobPermissions.LIST), 100);
        BlobContainerPermissions perms = new BlobContainerPermissions();
        perms.getSharedAccessPolicies().put("readperm", sp);
        perms.setPublicAccess(BlobContainerPublicAccessType.CONTAINER);
        container.uploadPermissions(perms);
        String sas = blob.generateSharedAccessSignature(sp, null);
        CloudBlockBlob sasBlob = new CloudBlockBlob(
                new URI(blob.getUri().toString() + "?" + blob.generateSharedAccessSignature(null, "readperm")));
        sasBlob.download(new ByteArrayOutputStream());
        CloudBlob blobFromUri = new CloudBlockBlob(
                PathUtility.addToQuery(blob.getStorageUri(), blob.generateSharedAccessSignature(null, "readperm")));
        assertEquals(StorageCredentialsSharedAccessSignature.class.toString(),
                blobFromUri.getServiceClient().getCredentials().getClass().toString());
        StorageCredentials creds = new StorageCredentialsSharedAccessSignature(
                blob.generateSharedAccessSignature(null, "readperm"));
        CloudBlobClient bClient = new CloudBlobClient(sasBlob.getServiceClient().getStorageUri(), creds);
        CloudBlockBlob blobFromClient = bClient.getContainerReference(blob.getContainer().getName())
                .getBlockBlobReference(blob.getName());
        assertEquals(StorageCredentialsSharedAccessSignature.class.toString(),
                blobFromClient.getServiceClient().getCredentials().getClass().toString());
        assertEquals(bClient, blobFromClient.getServiceClient());
        return sas;
    } 

I have added this line into code from reference of url provided earlier:

perms.setPublicAccess(BlobContainerPublicAccessType.CONTAINER);

I have code which gives me url for blob with token like :

https://accountName.blob.core.windows.net/directories/blobName?token

Still with this url, it's downloading the respective blob. What changes I should make in code while creating token, so that I can view blobs in browser itself without downloading?

Answer 1

First thing you would want to check is the content-type property of the blob. In all likelihood, the content type of the blob would be application/octet-stream (which is the default content type). Because of this the browser is not understanding what to do with this blob and thus downloading it. Please try to change the content type of the blob to appropriate value (e.g. image/png) and that should fix the problem.

Also I noticed that you're setting the container's ACL to BlobContainerPublicAccessType.CONTAINER. If you're doing this, then there's no need for you to create Shared Access Signature (SAS). Your blobs will be accessible simply by their URL (https://accountname.blob.core.windows.net/containername/blobname). SAS comes into play when the container's ACL is Private.

Answer 2

Blobs have binary data which could be just about anything - an image, video, document etc. When you click on the blob url it's similar to clicking on any url that point's to a file. The default action of a browser would be to download the file unless the browser can display the contents.

What the comment (To view the uploaded blobs in a browser..) implies is that for the blob to be publicly visible you need to set appropriate permissions. Once these permissions are set you can paste the url to the blob in a browser and it would be accessible.

To allow public access to the container you can use the following code -

public static void SetPublicContainerPermissions(CloudBlobContainer 
container)
{
    BlobContainerPermissions permissions = container.GetPermissions();
    permissions.PublicAccess = BlobContainerPublicAccessType.Container;
    container.SetPermissions(permissions);
}

You can find more about managing access to blobs in the doucmentation