Thread-safe OAuth 2.0 authorization code flow HTTP servlet that manages and persists end-user credentials.
This is designed to simplify the flow in which an end-user authorizes your web application to access their protected data. Your application then has access to their data based on an access token and a refresh token to refresh that access token when it expires. Your main servlet class should extend AbstractAuthorizationCodeServlet and implement the abstract methods. To get the persisted credential associated with the current request, call getCredential(). It is assumed that the end-user is authenticated by some external means by which a user ID is obtained. This user ID is used as the primary key for persisting the end-user credentials, and passed in via getUserId(HttpServletRequest). The first time an end-user arrives at your servlet, they will be redirected in the browser to an authorization page. Next, they will be redirected back to your site at the redirect URI selected in getRedirectUri(HttpServletRequest). The servlet to process that should extend AbstractAuthorizationCodeCallbackServlet, which should redirect back to this servlet on success.
Although this implementation is thread-safe, it can only process one request at a time. For a more performance-critical multi-threaded web application, instead use AuthorizationCodeFlow directly.
Return the persisted credential associated with the current request or null for none.
Returns the redirect URI for the given HTTP servlet request.
Loads the authorization code flow to be used across all HTTP servlet requests (only called during the first HTTP servlet request).
Handles user authorization by redirecting to the OAuth 2.0 authorization server.