google api , the problem of null refresh token

http://stackoverflow.com/questions/10827920/google-oauth-refresh-token-is-not-being-received

The

refresh_token

is only provided on the first authorization from the user. Subsequent authorizations, such as the kind you make while testing an OAuth2 integration, will not return the

refresh_token

again. :)

Go to your account security settings: https://www.google.com/settings/u/1/security.

Click the edit button next to "Authorizing applications and sites".

Then click "Revoke Access" next to your app.

The next OAuth2 request you make will return a

refresh_token

.

Alternatively, you can add the query parameter

approval_prompt=force

to the OAuth redirect (see Google's OAuth 2.0 for Web Server Applications page).

This will prompt the user to authorize the application again and will always return a

refresh_token

.