Verification Code Receivers

/**
 * OAuth 2.0 verification code receiver.
 * Implementation should be thread-safe.
 */
public interface VerificationCodeReceiver {
    
    /**
     * Returns the redirect URI to be used in the authorization request.
     * @return redirect URI string
     * @throws IOException if URI generation fails
     */
    String getRedirectUri() throws IOException;
    
    /**
     * Waits for a verification code from the user.
     * This method blocks until a code is received.
     * @return verification code string
     * @throws IOException if code reception fails
     */
    String waitForCode() throws IOException;
    
    /**
     * Releases any resources and stops any processes started.
     * @throws IOException if resource cleanup fails
     */
    void stop() throws IOException;
}

/**
 * OAuth 2.0 abstract verification code receiver that prompts user to paste the code 
 * copied from the browser. Implementation is thread-safe.
 */
public abstract class AbstractPromptReceiver implements VerificationCodeReceiver {
    
    /**
     * Prompts the user to enter the verification code via console input.
     * Continues prompting until a non-empty code is entered.
     * @return verification code entered by user
     */
    @Override
    public String waitForCode();
    
    /**
     * No-op implementation since no resources need to be stopped.
     */
    @Override  
    public void stop();
    
    // Abstract method - must be implemented by subclasses
    /**
     * Returns the redirect URI. Typically "urn:ietf:wg:oauth:2.0:oob" for out-of-band flows.
     * @return redirect URI for the authorization request
     * @throws IOException if URI generation fails  
     */
    public abstract String getRedirectUri() throws IOException;
}

import com.google.api.client.extensions.java6.auth.oauth2.AbstractPromptReceiver;

// Create a simple console-based receiver for out-of-band authorization
public class ConsoleReceiver extends AbstractPromptReceiver {
    @Override
    public String getRedirectUri() throws IOException {
        // Out-of-band redirect URI for manual code entry
        return "urn:ietf:wg:oauth:2.0:oob";
    }
}

// Usage in authorization flow
ConsoleReceiver receiver = new ConsoleReceiver();
AuthorizationCodeInstalledApp app = new AuthorizationCodeInstalledApp(flow, receiver);

// When authorize() is called:
// 1. Browser opens to authorization URL
// 2. User grants permission and copies the code
// 3. Console prompts: "Please enter code: "
// 4. User pastes the code and presses Enter
// 5. Authorization completes
Credential credential = app.authorize("user-id");

import com.google.api.client.extensions.java6.auth.oauth2.VerificationCodeReceiver;
import java.util.Scanner;

// Custom receiver that uses a GUI dialog instead of console
public class DialogReceiver implements VerificationCodeReceiver {
    private JDialog dialog;
    private String code;
    
    @Override
    public String getRedirectUri() throws IOException {
        return "urn:ietf:wg:oauth:2.0:oob";
    }
    
    @Override
    public String waitForCode() throws IOException {
        SwingUtilities.invokeLater(() -> {
            dialog = new JDialog();
            JTextField codeField = new JTextField(30);
            JButton okButton = new JButton("OK");
            
            okButton.addActionListener(e -> {
                code = codeField.getText();
                dialog.dispose();
            });
            
            dialog.add(new JLabel("Enter verification code:"));
            dialog.add(codeField);
            dialog.add(okButton);
            dialog.setModal(true);
            dialog.pack();
            dialog.setVisible(true);
        });
        
        // Wait for dialog completion
        while (code == null) {
            Thread.sleep(100);
        }
        return code;
    }
    
    @Override
    public void stop() throws IOException {
        if (dialog != null) {
            dialog.dispose();
        }
    }
}