(Lianja) Azure Blob - Get Tags (Check if Blob Exists)

See more Azure Cloud Storage Examples

Gets the user-defined tags for a specified blob. This can also be used as a way to check to see if a blob exists.

For more information, see https://learn.microsoft.com/en-us/rest/api/storageservices/get-blob-tags

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

loRest = createobject("CkRest")

// Connect to the Azure Storage Blob Service
llBTls = .T.
lnPort = 443
llBAutoReconnect = .T.
// In this example, the storage account name is "chilkat".
llSuccess = loRest.Connect("chilkat.blob.core.windows.net",lnPort,llBTls,llBAutoReconnect)
if (llSuccess <> .T.) then
    ? loRest.LastErrorText
    release loRest
    return
endif

// Provide Azure Cloud credentials for the REST call.
loAzAuth = createobject("CkAuthAzureStorage")
loAzAuth.AccessKey = "AZURE_ACCESS_KEY"
// The account name used here should match the 1st part of the domain passed in the call to Connect (above).
loAzAuth.Account = "chilkat"
loAzAuth.Scheme = "SharedKey"
loAzAuth.Service = "Blob"
// This causes the "x-ms-version: 2021-08-06" header to be automatically added.
loAzAuth.XMsVersion = "2021-08-06"
llSuccess = loRest.SetAuthAzureStorage(loAzAuth)

// Note: The application does not need to explicitly set the following
// headers: Content-Length, x-ms-date, Authorization.  These headers
// are automatically set by Chilkat.

// The Azure blob container is "test", the file is "helloWorld.txt"
// Add "?comp=tags" to get the user-defined tags instead of the actual blob content.
loSb = createobject("CkStringBuilder")
llSuccess = loRest.FullRequestNoBodySb("GET","/test/helloWorldajdfadf.txt?comp=tags",loSb)
if (llSuccess = .F.) then
    // Examine the request/response to see what happened.
    ? "response status code = " + str(loRest.ResponseStatusCode)
    ? "response status text = " + loRest.ResponseStatusText
    ? "response header: " + loRest.ResponseHeader
    ? "---"
    ? "LastRequestStartLine: " + loRest.LastRequestStartLine
    ? "LastRequestHeader: " + loRest.LastRequestHeader
    release loRest
    release loAzAuth
    release loSb
    return
endif

// A typical blob with no tags will return this:

// <?xml version="1.0" encoding="utf-8"?>
// <Tags><TagSet/></Tags>

// If the blob does not exist, you get this:

// <?xml version="1.0" encoding="utf-8"?>
// <Error>
//     <Code>BlobNotFound</Code>
//     <Message>The specified blob does not exist.
// 	RequestId:fcfefdd9-301e-001a-2135-3a23d2000000
// 	Time:2023-02-06T14:17:00.7805577Z
//     </Message>
// </Error>

? loSb.GetAsString()

// To see if we got Tags or an Error, then examine the XML.
loXml = createobject("CkXml")
loXml.LoadSb(loSb,.T.)

// Examine the tag..
if (loXml.TagEquals("Tags") = .T.) then
    ? "Blob exists!"
else

    if (loXml.ChildContentMatches("Code","BlobNotFound",.T.) = .T.) then
        ? "Blob does not exist."
    else
        ? "Some other error..."
    endif

endif

? "Success."


release loRest
release loAzAuth
release loSb
release loXml