(Ruby) Refresh GMail SMTP OAuth2 Access Token

Demonstrates how to refresh an access token for sending email via GMail (SMTP).

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.

# See Get GMail SMTP Access Token 
# for sample code showing how to obtain a GMail SMTP access token for desktop apps.

# It is assumed we previously obtained an OAuth2 access token for GMail (one with a scope for sending email).

jsonToken = Chilkat::CkJsonObject.new()
success = jsonToken.LoadFile("qa_data/tokens/_gmailSmtp.json")
if (success != true)
    print "Failed to load _gmailSmtp.json" + "\n";
    exit
end

# The access token JSON looks something like this:

# 	{ 
# 	 "access_token": "abac.Ci-ZabcdF37-NUrmSzxbHxTsMbtlN-uPfabcdAQN_2ekzj0s5ofCzRabcdTDMGaa2Q",
# 	 "token_type": "Bearer",
# 	 "expires_in": 3600,
# 	 "refresh_token": "1/lEe5abcdNJ77eOSDBabcdkQGVmDalkwabcdR2Hatbo"
# 	}
# 

oauth2 = Chilkat::CkOAuth2.new()

oauth2.put_TokenEndpoint("https://www.googleapis.com/oauth2/v4/token")

# Replace these with actual values.
oauth2.put_ClientId("GOOGLE-CLIENT-ID")
oauth2.put_ClientSecret("GOOGLE-CLIENT-SECRET")

# Get the "refresh_token"
oauth2.put_RefreshToken(jsonToken.stringOf("refresh_token"))

# Send the HTTP POST to refresh the access token..
success = oauth2.RefreshAccessToken()
if (success != true)
    print oauth2.lastErrorText() + "\n";
    exit
end

# The response contains a new access token, but we must keep
# our existing refresh token for when we need to refresh again in the future.
jsonToken.UpdateString("access_token",oauth2.accessToken())

# Save the new JSON access token response to a file.
sbJson = Chilkat::CkStringBuilder.new()
jsonToken.put_EmitCompact(false)
jsonToken.EmitSb(sbJson)
sbJson.WriteFile("qa_data/tokens/_gmailSmtp.json","utf-8",false)

print "OAuth2 authorization granted!" + "\n";
print "New Access Token = " + oauth2.accessToken() + "\n";