(Ruby) Refresh Access Token on 401 Unauthorized and Retry (Service Account)

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Demonstrates how to handle an expired access token error, refresh the token, and retry the request. (In this case, the request is to download an object from Google Cloud Storage.)

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

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

# This example uses a previously obtained access token having permission for the 
# scope "https://www.googleapis.com/auth/cloud-platform"

# In this example, Get Google Cloud Storage OAuth2 Access Token, 
# the service account access token was saved to a text file.  This example fetches the access token from the file..
sbToken = Chilkat::CkStringBuilder.new()
success = sbToken.LoadFile("qa_data/tokens/googleCloudStorageAccessToken.txt","utf-8")
if (success == false)
    print "Failed to load access token." + "\n";
    exit
end

http = Chilkat::CkHttp.new()

http.put_AuthToken(sbToken.getAsString())

# Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
http.SetUrlVar("bucket_name","chilkat-ocean")
http.SetUrlVar("object_name","starfish.jpg")
url = "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media"

# If there is an error response, then we didn't actually download the file data,
# but instead we downloaded an error response..
fileData = Chilkat::CkBinData.new()
success = http.DownloadBd(url,fileData)
responseCode = http.get_LastStatus()
if ((success == false) and (responseCode != 401))
    print http.lastErrorText() + "\n";
    exit
end

if (responseCode == 401)
    print "Received 401 Unauthorized response. Attempting to refresh the access token..." + "\n";

    # May be that the access token expired.
    # Load our JSON key and request a new access token, then retry the original request.
    fac = Chilkat::CkFileAccess.new()
    jsonKey = fac.readEntireTextFile("qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json","utf-8")
    if (fac.get_LastMethodSuccess() != true)
        print fac.lastErrorText() + "\n";
        exit
    end

    gAuth = Chilkat::CkAuthGoogle.new()
    gAuth.put_JsonKey(jsonKey)
    gAuth.put_Scope("https://www.googleapis.com/auth/cloud-platform")
    gAuth.put_ExpireNumSeconds(3600)
    gAuth.put_SubEmailAddress("")

    tlsSock = Chilkat::CkSocket.new()
    success = tlsSock.Connect("www.googleapis.com",443,true,5000)
    if (success != true)
        print tlsSock.lastErrorText() + "\n";
        exit
    end

    success = gAuth.ObtainAccessToken(tlsSock)
    if (success != true)
        print gAuth.lastErrorText() + "\n";
        exit
    end

    fac.WriteEntireTextFile("qa_data/tokens/googleCloudStorageAccessToken.txt",gAuth.accessToken(),"utf-8",false)

    # Retry the original request.
    http.put_AuthToken(gAuth.accessToken())
    success = http.DownloadBd(url,fileData)
    if (success == false)
        print http.lastErrorText() + "\n";
        exit
    end

end

if (responseCode != 200)
    # Get the error response
    sbErrorResponse = Chilkat::CkStringBuilder.new()
    sbErrorResponse.AppendBd(fileData,"utf-8",0,0)
    print "Error response code = " + responseCode.to_s() + "\n";
    print "Error:" + "\n";
    print sbErrorResponse.getAsString() + "\n";
    exit
end

print "Success." + "\n";

# Save the downloaded data to a file.
success = fileData.WriteFile("qa_output/starfish.jpg")