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# Google OAuth Client Java 6
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Google OAuth Client Java 6 provides Java 6+ extensions to the Google OAuth Client Library for Java. It focuses on OAuth 2.0 verification code receivers and credential persistence mechanisms for installed applications, command-line tools, and desktop applications that need to handle OAuth 2.0 authorization flows.
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## Package Information
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- **Package Name**: google-oauth-client-java6
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- **Package Type**: maven
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- **Language**: Java
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- **Group ID**: com.google.oauth-client  
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- **Artifact ID**: google-oauth-client-java6
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- **Installation**: 
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  ```xml
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  <dependency>
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    <groupId>com.google.oauth-client</groupId>
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    <artifactId>google-oauth-client-java6</artifactId>
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    <version>1.39.0</version>
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  </dependency>
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  ```
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## Core Imports
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```java
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import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
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import com.google.api.client.extensions.java6.auth.oauth2.VerificationCodeReceiver;
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import com.google.api.client.extensions.java6.auth.oauth2.AbstractPromptReceiver;
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import com.google.api.client.extensions.java6.auth.oauth2.FileCredentialStore;
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import com.google.api.client.auth.oauth2.AuthorizationCodeFlow;
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import com.google.api.client.auth.oauth2.Credential;
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```
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## Basic Usage
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```java
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import com.google.api.client.auth.oauth2.AuthorizationCodeFlow;
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import com.google.api.client.auth.oauth2.BearerToken;
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import com.google.api.client.auth.oauth2.Credential;
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import com.google.api.client.auth.oauth2.ClientParametersAuthentication;
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import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
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import com.google.api.client.extensions.java6.auth.oauth2.AbstractPromptReceiver;
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import com.google.api.client.http.HttpTransport;
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import com.google.api.client.http.GenericUrl;
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import com.google.api.client.json.JsonFactory;
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// Create a custom prompt receiver
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class ConsoleReceiver extends AbstractPromptReceiver {
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    @Override
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    public String getRedirectUri() {
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        return "urn:ietf:wg:oauth:2.0:oob";
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    }
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}
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// Set up OAuth flow for installed application
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AuthorizationCodeFlow flow = new AuthorizationCodeFlow.Builder(
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    BearerToken.authorizationHeaderAccessMethod(),
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    httpTransport,      // Your HttpTransport instance
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    jsonFactory,        // Your JsonFactory instance  
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    new GenericUrl("https://oauth2.googleapis.com/token"), // Token server URL
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    new ClientParametersAuthentication("your-client-id", "your-client-secret"), // Client authentication
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    "your-client-id",   // Your OAuth 2.0 client ID
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    "https://accounts.google.com/o/oauth2/auth") // Authorization server URL
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    .build();
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// Authorize user
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ConsoleReceiver receiver = new ConsoleReceiver();
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AuthorizationCodeInstalledApp app = new AuthorizationCodeInstalledApp(flow, receiver);
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Credential credential = app.authorize("user123");
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```
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## Architecture
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Google OAuth Client Java 6 is built around several key components:
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- **Verification Code Receivers**: Interface and implementations for receiving OAuth 2.0 verification codes
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- **Authorization Flow Integration**: Seamless integration with Google OAuth Client's authorization flows
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- **Credential Persistence**: File-based credential storage for maintaining tokens across application restarts (deprecated components)
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- **Browser Integration**: Automatic browser launching with fallback to manual URL copy-paste
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## Capabilities
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### Authorization Code Flow for Installed Apps
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Complete OAuth 2.0 authorization flow implementation for installed applications, including browser integration and credential management.
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```java { .api }
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public class AuthorizationCodeInstalledApp {
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    public AuthorizationCodeInstalledApp(
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        AuthorizationCodeFlow flow, 
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        VerificationCodeReceiver receiver);
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    public AuthorizationCodeInstalledApp(
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        AuthorizationCodeFlow flow, 
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        VerificationCodeReceiver receiver, 
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        Browser browser);
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    public Credential authorize(String userId) throws IOException;
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    public final AuthorizationCodeFlow getFlow();
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    public final VerificationCodeReceiver getReceiver();
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    public static void browse(String url);
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}
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```
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[Authorization Code Flow](./authorization-flow.md)
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### Verification Code Receivers
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Interface and implementations for receiving OAuth 2.0 verification codes from users during the authorization process.
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```java { .api }
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public interface VerificationCodeReceiver {
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    String getRedirectUri() throws IOException;
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    String waitForCode() throws IOException;
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    void stop() throws IOException;
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}
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public abstract class AbstractPromptReceiver implements VerificationCodeReceiver {
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    public String waitForCode();
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    public void stop();
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    public abstract String getRedirectUri() throws IOException;
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}
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// Browser interface for custom browser implementations
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public static interface Browser {
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    public void browse(String url) throws IOException;
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}
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public static class DefaultBrowser implements Browser {
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    @Override
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    public void browse(String url) throws IOException;
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}
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```
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[Verification Code Receivers](./verification-receivers.md)
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### File-Based Credential Storage (Deprecated)
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Legacy file-based credential storage system for persisting OAuth 2.0 credentials. These components are deprecated in favor of `FileDataStoreFactory`.
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```java { .api }
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@Deprecated
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public class FileCredentialStore implements CredentialStore {
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    public FileCredentialStore(File file, JsonFactory jsonFactory) throws IOException;
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    public void store(String userId, Credential credential) throws IOException;
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    public boolean load(String userId, Credential credential);
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    public void delete(String userId, Credential credential) throws IOException;
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}
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```
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[File Credential Storage](./file-credential-storage.md)
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## Migration Notes
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The file-based credential storage classes (`FileCredentialStore`, `FilePersistedCredential`, `FilePersistedCredentials`) are deprecated. Use `FileDataStoreFactory` with `StoredCredential` instead:
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```java
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// Deprecated approach
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FileCredentialStore store = new FileCredentialStore(file, jsonFactory);
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// Recommended approach  
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FileDataStoreFactory dataStoreFactory = new FileDataStoreFactory(dataDirectory);
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DataStore<StoredCredential> dataStore = StoredCredential.getDefaultDataStore(dataStoreFactory);
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```