Hello AvinashaN,
Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.
Each of our current OAuth2 authorization flows requires the use of a browser to authorize an application on an account, but you should only need to do this once. After an account has authorized your application, you can utilize refresh tokens to maintain access and fully automate your application. For a server side application, I would recommend using either the Authorization Code flow or the Device flow. I’ll include documentation for both flows below as well as some instructions for starting out with the Authorization Code flow. The main difference between these flows is that the Device Flow does not require using redirect URLs, callbacks, or the client secret. Instead, it requires getting a device_code, and then the application’s client_id and the device_code are used to get an access token.
Authorization Code Flow:
https://developer.constantcontact.com/api_guide/server_flow.html
Device Flow:
https://developer.constantcontact.com/api_guide/device_flow.html
To get started with the V3 API, you’ll want to start by going through the V3 API OAuth2 Authorization Code Flow. Please note, after step 1, you should set up step 4 before proceeding, because the authorization code from steps 2 and 3 only has a lifespan of 5 minutes.
V3 API OAuth2 Authorization Code Flow
https://v3.developer.constantcontact.com/api_guide/server_flow.html
Once you have your first set of tokens, you’ll want to set the access token and the refresh token as values for corresponding variables in your application, so that when your program runs through step 8 of the OAuth2 Authorization Code Flow to get the new set of tokens it can assign the updated values to those variables to maintain an authenticated connection.
You can either have the application refresh the tokens on a timer based on the life of the access token (access token lifetime is a static 24 hours), or you can check to see if the access token is still active before each submission, and then use the refresh token to generate a new set of tokens if not.
In order to parse the JWT access token for the expiration date/time and/or granted scopes, I'd suggest looking for a standalone JWT decoder tool or setting up a decoder within your program’s code so that it can programmatically verify the remaining lifetime of the access token before attempting to refresh.
[3rd party resource] JWT Decoder Tool Examples:
https://jwt.io/#debugger-io
https://developer.pingidentity.com/en/tools/jwt-decoder.html
[3rd party resource] Epoch & Unix Timestamp Conversion Tool Example:
https://www.epochconverter.com/
If you want your application to parse the JWT programmatically in your program’s code (the example we currently offer in the documentation is only in Java at this time), you can find instructions online regarding how to do this in different languages.
The OpenID Foundation maintains a list of libraries implementing JWT and JOSE specs, which may be a good starting point. Their list can be found here: https://openid.net/developers/jwt/
Once authentication is set up, and you’re able to complete Step 8 (Refresh the Access Token), you can then use your current Access Token variable value to make calls to the API endpoints.
Please have a look and let us know if you have any other questions!
Regards,
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