Refresh token and reuse this token to get new access token java

Question

How do I get the refresh token and the access token from the first time authorization code? And, how do I reuse this refresh token to get a new access token to upload to Google Drive using the Java API? This is not a web application. It's in Java Swing code.

Answer 1

We can reuse the refresh token to get new access token by following code

public class OAuthRefreshToken implements CredentialRefreshListener  {

    public static GoogleCredential getAccessTokenFromRefreshToken( String refreshToken, HttpTransport transport, com.google.api.client.json.JsonFactory jsonFactory, String CLIENT_ID, String CLIENT_SECRET) throws IOException
    {
        GoogleCredential.Builder credentialBuilder = new GoogleCredential.Builder()
        .setTransport(transport).setJsonFactory(jsonFactory)
        .setClientSecrets(CLIENT_ID, CLIENT_SECRET);
        credentialBuilder.addRefreshListener(new OAuthRefreshToken());

        GoogleCredential credential = credentialBuilder.build();
        credential.setRefreshToken(refreshToken);
        credential.refreshToken();
        return credential;
    }

    @Override
    public void onTokenErrorResponse(Credential arg0, TokenErrorResponse arg1)
            throws IOException {
        // TODO Auto-generated method stub
        System.out.println("Error occured !");
        System.out.println(arg1.getError());
    }

    @Override
    public void onTokenResponse(Credential arg0, TokenResponse arg1)
            throws IOException {
        // TODO Auto-generated method stub
        System.out.println(arg0.getAccessToken());
        System.out.println(arg0.getRefreshToken());
    }

}

Answer 2

Here is a solution I recently made up from the basic example in the Google Drive docs and some experimenting: The IApiKey contains the static strings CLIENT_ID, and so on. ITokenPersistence is an interface which allows to load and save a token (as String). It decouples the persistence mechanism (I used Preferences for an Eclipse e4 RCP application) from the Uploader. This can be as simple as storing the token in a file The IAthorizationManager is an interface which is is used to let the user grant acces and enter the code to create the refresh token. I implemented a Dialog containing a browser widget to grant access and a text box to copy and paste the code to. The custom exception GoogleDriveException hides the API classes from the rest of the code.

public final class Uploader implements IApiKey {

    public static final String TEXT_PLAIN = "text/plain";

    private final ITokenPersistence tokenManager;
    private final IAuthorizationManager auth;

    public Uploader(final ITokenPersistence tm, final IAuthorizationManager am) {
        this.tokenManager = tm;
        this.auth = am;
    }

    private GoogleCredential createCredentialWithRefreshToken(
            final HttpTransport transport,
            final JsonFactory jsonFactory,
            final String clientId,
            final String clientSecret,
            final TokenResponse tokenResponse) {
        return new GoogleCredential.Builder().setTransport(transport)
                .setJsonFactory(jsonFactory)
                .setClientSecrets(clientId, clientSecret)
                .build()
                .setFromTokenResponse(tokenResponse);
    }

    /**
     * Upload the given file to Google Drive.
     * <P>
     * The name in Google Drive will be the same as the file name.
     * @param fileContent a file of type text/plain
     * @param description a description for the file in Google Drive
     * @return Answer the ID of the uploaded file in Google Drive.
     *         Answer <code>null</code> if the upload failed.
     * @throws IOException
     * @throws {@link GoogleDriveException} when a <code>TokenResponseException</code> had been
     *         intercepted while inserting (uploading) the file.
     */
    public String upload(final java.io.File fileContent, final String description) throws IOException, GoogleDriveException {
        HttpTransport httpTransport = new NetHttpTransport();
        JsonFactory jsonFactory = new JacksonFactory();

        // If we do not already have a refresh token a flow is created to get a refresh token.
        // To get the token the user has to visit a web site and enter the code afterwards
        // The refresh token is saved and may be reused.
        final GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
                httpTransport,
                jsonFactory,
                CLIENT_ID,
                CLIENT_SECRET,
                Arrays.asList(DriveScopes.DRIVE))
        .setAccessType("offline")
        .setApprovalPrompt("auto").build();

        final String url = flow.newAuthorizationUrl().setRedirectUri(REDIRECT_URI).build();
        final String refreshToken = this.tokenManager.loadRefreshToken();

        GoogleCredential credential = null;
        if( refreshToken == null ) {
            // no token available: get one
            String code = this.auth.authorize(url);
            GoogleTokenResponse response = flow.newTokenRequest(code).setRedirectUri(REDIRECT_URI).execute();
            this.tokenManager.saveRefreshToken(response.getRefreshToken());
            credential = this.createCredentialWithRefreshToken(httpTransport, jsonFactory, CLIENT_ID, CLIENT_SECRET, response);
        }
        else {
            // we have a token, if it is expired or revoked by the user the service call (see below) may fail
            credential = new GoogleCredential.Builder()
            .setJsonFactory(jsonFactory)
            .setTransport(httpTransport)
            .setClientSecrets(CLIENT_ID, CLIENT_SECRET)
            .build();
            credential.setRefreshToken(refreshToken);
        }

        //Create a new authorized API client
        final Drive service = new Drive.Builder(httpTransport, jsonFactory, credential)
        .setApplicationName(APP_NAME)
        .build();

        //Insert a file
        final File body = new File();
        body.setTitle(fileContent.getName());
        body.setDescription(description);
        body.setMimeType(TEXT_PLAIN);
        final FileContent mediaContent = new FileContent(TEXT_PLAIN, fileContent);

        try {
            final File file = service.files().insert(body, mediaContent).execute();
            return ( file != null ) ? file.getId() : null;
        } catch (TokenResponseException e) {
            e.printStackTrace();
            throw new GoogleDriveException(e.getDetails().getErrorDescription(), e.getCause());
        }
    }

}