(Java) Dropbox: OAuth2 Authorization to Obtain an Access Token

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This example runs the OAuth 2.0 authorization flow that lets the user sign in to Dropbox and authorize your app.

Note: This example requires Chilkat v10.1.2 or greater.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // For more information about the OAuth2, see OAuth 2.0 Authorization Flow

    CkOAuth2 oauth2 = new CkOAuth2();

    // The port should match the Authorized Redirect URL in your Dropbox app, 
    // which would look like "http://localhost:3017/"
    oauth2.put_ListenPort(3017);

    // IMPORTANT: One of the OAuth2 redirect URIs for your Dropbox app must be
    // exactly this string:  http://localhost:3017/

    oauth2.put_AuthorizationEndpoint("https://www.dropbox.com/oauth2/authorize");
    oauth2.put_TokenEndpoint("https://api.dropboxapi.com/oauth2/token");

    // Replace this with your actual Dropbox App Key
    oauth2.put_ClientId("DROPBOX_APP_KEY");

    // This is for Require Proof Key for Code Exchange (PKCE)
    // See OAuth2 PKCE Explained
    oauth2.put_CodeChallenge(true);
    oauth2.put_CodeChallengeMethod("S256");

    // Add token_access_type=offline to also get a refresh token in the response
    oauth2.AddAuthQueryParam("token_access_type","offline");

    // Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
    String url = oauth2.startAuth();
    if (oauth2.get_LastMethodSuccess() != true) {
        System.out.println(oauth2.lastErrorText());
        return;
        }

    System.out.println("url = " + url);

    // Launch the default browser on the system and navigate to the url.
    // The LaunchBrowser method was added in Chilkat v10.1.2.
    boolean success = oauth2.LaunchBrowser(url);
    if (success == false) {
        System.out.println(oauth2.lastErrorText());
        return;
        }

    // Wait for the user to approve or deny authorization in the browser.
    int numMsWaited = 0;
    while ((numMsWaited < 90000) && (oauth2.get_AuthFlowState() < 3)) {
        oauth2.SleepMs(100);
        numMsWaited = numMsWaited+100;
        }

    // If the browser does not respond within the specified time, AuthFlowState will be:
    // 
    // 1: Waiting for Redirect - The OAuth2 background thread is waiting for the browser's redirect request.
    // 2: Waiting for Final Response - The thread is awaiting the final access token response.
    // In either case, cancel the background task initiated by StartAuth.

    if (oauth2.get_AuthFlowState() < 3) {
        oauth2.Cancel();
        System.out.println("No response from the browser!");
        return;
        }

    // Check AuthFlowState to determine if authorization was granted, denied, or failed:
    // 
    // 3: Success - OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
    // 4: Access Denied - OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
    // 5: Failure - OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

    if (oauth2.get_AuthFlowState() == 5) {
        System.out.println("OAuth2 failed to complete.");
        System.out.println(oauth2.failureInfo());
        return;
        }

    if (oauth2.get_AuthFlowState() == 4) {
        System.out.println("OAuth2 authorization was denied.");
        System.out.println(oauth2.accessTokenResponse());
        return;
        }

    if (oauth2.get_AuthFlowState() != 3) {
        System.out.println("Unexpected AuthFlowState:" + oauth2.get_AuthFlowState());
        return;
        }

    System.out.println("OAuth2 authorization granted!");

    CkJsonObject json = new CkJsonObject();
    json.Load(oauth2.accessTokenResponse());
    json.put_EmitCompact(false);

    System.out.println("Access Token Response = " + json.emit());

    // A sample access token response:

    // {
    //   "access_token": "...",
    //   "token_type": "bearer",
    //   "expires_in": 14399,
    //   "refresh_token": "...",
    //   "scope": "account_info.read",
    //   "uid": "562542581",
    //   "account_id": "dbid:AACQhDS0E3_Vb72Ynd0F-GxGWdTI2qcTHzA"
    // }

    System.out.println("Access Token = " + oauth2.accessToken());

    // Save the JSON access token response to a file for subsequent use..
    json.WriteFile("qa_data/tokens/dropbox.json");
  }
}