如何通过API让用户输入凭证实现Google Drive文件上传？

核心思路 #

针对非技术用户，采用OAuth 2.0 桌面应用授权流程是最优解：用户只需在Google Cloud控制台生成简单凭证，通过工具引导完成一次授权，即可得到可长期复用的刷新令牌（Refresh Token），后续上传无需重复授权。

用户侧凭证生成步骤（非技术友好） #

• 打开Google Cloud控制台，创建新项目（或使用现有项目）
• 搜索并启用「Google Drive API」
• 进入「API和服务」→「凭据」页面，点击「创建凭据」→「OAuth 客户端ID」
• 应用类型选择「桌面应用」，填写任意名称后完成创建，下载生成的JSON文件
• 打开你的工具，点击「生成Refresh Token」按钮，选择下载的JSON文件，工具会自动打开浏览器引导你完成Google账号授权，授权后工具会提取并展示Client ID、Client Secret、Refresh Token，将这三个值保存到工具UI中即可

Java 实现核心代码 #

1. 依赖引入（Maven） #

<dependency>
    <groupId>com.google.oauth-client</groupId>
    <artifactId>google-oauth-client-java6</artifactId>
    <version>1.34.1</version>
</dependency>
<dependency>
    <groupId>com.google.apis</groupId>
    <artifactId>google-api-services-drive</artifactId>
    <version>v3-rev20240425-2.0.0</version>
</dependency>

2. 认证与上传逻辑 #

import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
import com.google.api.client.extensions.jetty.auth.oauth2.LocalServerReceiver;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.gson.GsonFactory;
import com.google.api.services.drive.Drive;
import com.google.api.services.drive.DriveScopes;
import com.google.api.services.drive.model.File;

import java.io.IOException;
import java.security.GeneralSecurityException;
import java.util.Collections;
import java.util.List;

public class GoogleDriveUploader {
    private static final String APP_NAME = "你的工具名称";
    private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();
    private static final List<String> UPLOAD_SCOPES = Collections.singletonList(DriveScopes.DRIVE_FILE);

    // 生成Refresh Token（用户首次授权用）
    public static Credential generateRefreshToken(String clientId, String clientSecret) throws IOException {
        GoogleClientSecrets.Details details = new GoogleClientSecrets.Details();
        details.setClientId(clientId);
        details.setClientSecret(clientSecret);
        GoogleClientSecrets clientSecrets = new GoogleClientSecrets().setInstalled(details);

        GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
                GoogleNetHttpTransport.newTrustedTransport(), JSON_FACTORY, clientSecrets, UPLOAD_SCOPES)
                .setAccessType("offline") // 必须设置才能获取Refresh Token
                .build();
        
        LocalServerReceiver receiver = new LocalServerReceiver.Builder().setPort(8888).build();
        return new AuthorizationCodeInstalledApp(flow, receiver).authorize("user");
    }

    // 通过已有Refresh Token创建认证凭证
    private static Credential getCredentialFromRefreshToken(String clientId, String clientSecret, String refreshToken) throws IOException {
        Credential credential = new Credential.Builder(com.google.api.client.auth.oauth2.BearerToken.authorizationHeaderAccessMethod())
                .setTransport(GoogleNetHttpTransport.newTrustedTransport())
                .setJsonFactory(JSON_FACTORY)
                .setTokenServerUrl(new com.google.api.client.http.GenericUrl("https://oauth2.googleapis.com/token"))
                .setClientAuthentication(new com.google.api.client.googleapis.auth.oauth2.GoogleClientAuthentication(clientId, clientSecret))
                .build();
        
        credential.setRefreshToken(refreshToken);
        credential.refreshToken(); // 自动获取有效Access Token
        return credential;
    }

    // 上传图片到Google Drive
    public static String uploadImage(String imagePath, String clientId, String clientSecret, String refreshToken) throws IOException, GeneralSecurityException {
        Drive driveService = new Drive.Builder(GoogleNetHttpTransport.newTrustedTransport(), JSON_FACTORY, 
                getCredentialFromRefreshToken(clientId, clientSecret, refreshToken))
                .setApplicationName(APP_NAME)
                .build();

        File fileMetadata = new File();
        fileMetadata.setName(new java.io.File(imagePath).getName());
        // 可选：指定上传到特定文件夹，替换为你的文件夹ID
        // fileMetadata.setParents(Collections.singletonList("your-folder-id"));

        com.google.api.client.http.FileContent mediaContent = new com.google.api.client.http.FileContent("image/jpeg", new java.io.File(imagePath));
        File uploadedFile = driveService.files().create(fileMetadata, mediaContent)
                .setFields("id")
                .execute();

        return uploadedFile.getId(); // 返回上传后的文件ID，可用于后续访问
    }
}

3. UI交互建议 #

• 提供三个输入框：Client ID、Client Secret、Refresh Token
• 添加「生成Refresh Token」按钮：点击后让用户选择从Google Cloud下载的JSON文件，工具解析出Client ID和Client Secret，调用generateRefreshToken方法打开浏览器授权，授权成功后自动填充三个输入框
• 上传按钮：调用uploadImage方法，传入用户输入的三个凭证参数和图片路径

内容的提问来源于stack exchange，提问作者Mike Q