Lua

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. Lua

local chilkat = require("chilkat")

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

local rest = chilkat.Rest.new()

-- Connect to the Azure Storage Blob Service
local bTls = true
local port = 443
local bAutoReconnect = true
-- In this example, the storage account name is "chilkat".
local success = rest:connect("chilkat.blob.core.windows.net", port, bTls, bAutoReconnect)
if not success then
    print(rest.last_error_text)
    return
end

-- Provide Azure Cloud credentials for the REST call.
local azAuth = chilkat.AuthAzureStorage.new()
azAuth.access_key = "AZURE_ACCESS_KEY"
-- The account name used here should match the 1st part of the domain passed in the call to Connect (above).
azAuth.account = "chilkat"
azAuth.scheme = "SharedKey"
azAuth.service = "Blob"
-- This causes the "x-ms-version: 2021-08-06" header to be automatically added.
azAuth.xms_version = "2021-08-06"
success = rest:set_auth_azure_storage(azAuth)

-- 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.
local sb = chilkat.StringBuilder.new()
success = rest:full_request_no_body_sb("GET", "/test/helloWorldajdfadf.txt?comp=tags", sb)
if not success then
    -- Examine the request/response to see what happened.
    print("response status code = " .. rest.response_status_code)
    print("response status text = " .. rest.response_status_text)
    print("response header: " .. rest.response_header)
    print("---")
    print("LastRequestStartLine: " .. rest.last_request_start_line)
    print("LastRequestHeader: " .. rest.last_request_header)
    return
end

-- 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>

print(sb:get_as_string())

-- To see if we got Tags or an Error, then examine the XML.
local xml = chilkat.Xml.new()
xml:load_sb(sb, true)

-- Examine the tag..
if xml:tag_equals("Tags") then
    print("Blob exists!")
else

    if xml:child_content_matches("Code", "BlobNotFound", true) then
        print("Blob does not exist.")
    else
        print("Some other error...")
    end
end

print("Success.")