JAVA使用Google drive的API服务

JAVA 使用 Google drive 的 API 服务

遵循Google develop操作指示 (英文指导DriveJava Quickstart)。可能用的人太少了，这个step写的和米共一样。可能是我看不懂en,也可能是我🧠不太好使。

首先需要去注册你的软件😄
-别问为什么这么麻烦，Google就是脸比较大，欠打。
-去这个网站 (注册和生成jsonOAuth client ID credentials)生成credentials.json文件。
-是desktop哦，记得不要选错。
-下载下来的json文件不叫这个名字？难道你不会自己改么？

改build.gradle
记得改sourceCompatibility 和targetCompatibility

apply plugin: 'java'
apply plugin: 'application'

mainClassName = 'SheetsQuickstart'
sourceCompatibility = 11   //记得改这两个东西，你用哪个版本jdk就改成哪个版本的jdk
targetCompatibility = 11   //记得改这两个东西，你用哪个版本jdk就改成哪个版本的jdk
version = '1.0'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'com.google.api-client:google-api-client:1.33.0'
    implementation 'com.google.oauth-client:google-oauth-client-jetty:1.32.1'
    implementation 'com.google.apis:google-api-services-sheets:v4-rev20210629-1.32.1'
}

接下来就可以获取drive的文件了

文件的ID就是你发文件网址的后面部分（看起来像hash code的那部分，不要带edit/啥啥啥的）
每次跳到网站要你同意使用google drive的权限都会生成一个token.如果你需要换账号则需要删除这个token.
List SCOPES改变的是使用drive的权限，下面代码的列子是权限最大的
第一个是生成drive service,其实就是建立TCP链接
第二个function是下载文件中的每个文件中的所有图片 (搜索文件的语法Search query terms and operators)
第三个function是上传文件
第四个function是删除文件夹中的所有文件

可能运行第一次会教你去注册google的api服务，说你的服务没有开启。反正报错会给你一个链接，自己点进去看就好了。

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.googleapis.json.GoogleJsonResponseException;
import com.google.api.client.http.AbstractInputStreamContent;
import com.google.api.client.http.FileContent;
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.client.util.store.FileDataStoreFactory;
import com.google.api.services.drive.Drive;
import com.google.api.services.drive.DriveScopes;
import com.google.api.services.drive.model.File;
import com.google.api.services.drive.model.FileList;
import javafx.util.Pair;

import java.io.*;
import java.security.GeneralSecurityException;
import java.util.*;

/* class to demonstarte use of Drive files list API */
public class DriveQuickstart {
    /** Application name. */
    private static final String APPLICATION_NAME = "Google Drive API Java Quickstart";
    /** Global instance of the JSON factory. */
    private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();
    /** Directory to store authorization tokens for this application. */
    private static final String TOKENS_DIRECTORY_PATH = "drivetokens";

    /**
     * Global instance of the scopes required by this quickstart.
     * If modifying these scopes, delete your previously saved tokens/ folder.
     */
    private static final List<String> SCOPES = Collections.singletonList(DriveScopes.DRIVE);
    private static final String CREDENTIALS_FILE_PATH = "/credentials.json";

    private static Credential drive_token = null;
    private static Drive service = null;

    /**
     * init the drive.
     * @throws IOException If the credentials.json file cannot be found.
     */
    public DriveQuickstart() throws IOException, GeneralSecurityException {
        // Load client secrets.
        final NetHttpTransport HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();

        InputStream in = Main.class.getResourceAsStream(CREDENTIALS_FILE_PATH);
        if (in == null) {
            throw new FileNotFoundException("Resource not found: " + CREDENTIALS_FILE_PATH);
        }
        GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY, new InputStreamReader(in));

        // Build flow and trigger user authorization request.
        GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
                HTTP_TRANSPORT, JSON_FACTORY, clientSecrets, SCOPES)
                .setDataStoreFactory(new FileDataStoreFactory(new java.io.File(TOKENS_DIRECTORY_PATH)))
                .setAccessType("offline")
                .build();
        LocalServerReceiver receiver = new LocalServerReceiver.Builder().setPort(8888).build();
        Credential credential = new AuthorizationCodeInstalledApp(flow, receiver).authorize("user");
        //returns an authorized Credential object.
        drive_token = credential;

        service = new Drive.Builder(HTTP_TRANSPORT, JSON_FACTORY, credential)
                .setApplicationName(APPLICATION_NAME)
                .build();
    }

    public static List<File> get_file() throws IOException, GeneralSecurityException {
        //item-picture-upload
        //mimeType != 'application/vnd.google-apps.folder'

        // Print the names and IDs for all files.
        FileList result = service.files().list()
                .setQ("'11PJEUZl8QmZlNSl23_AfF3cjxKa-wgJH' in parents")
                .setFields("nextPageToken, files(id, name)")
                .execute();
        List<File> files = result.getFiles();

        List<String> folderids = new ArrayList<>();
        if (files == null || files.isEmpty()) {
            System.out.println("No files found.");
        } else {
            System.out.println("Files:");
            for (File file : files) {
                folderids.add(file.getId());
                System.out.printf("%s (%s)\n", file.getName(), file.getId());
            }
        }


        List<File> imgs = new ArrayList<>();
        if(folderids.size()!= 0){
            for(String folderid : folderids){
                FileList images = service.files().list()
                        .setQ( "'" + folderid+"'"+" in parents")
                        .setFields("nextPageToken, files(id, name)")
                        .execute();
                List<File> img_list = images.getFiles();
                if (img_list == null || img_list.isEmpty()) {
                    System.out.println("No imgs found in folder: "+ folderid);
                } else {
                    System.out.println(folderid+"  imges num: "+ img_list.size());
                    imgs.addAll(img_list);
                }
            }
        }
        else{
            System.out.println("no folders in this shared folder");
        }

        return imgs;

    }


    public void uploadBasic(List<Pair<String, File>> imgs, String realFolderId) throws IOException{
        //clear this folder first
        clear_folder("1RWaZWyCOABkoOUpZ2DJBBcGOrlBGv_lE");
        Drive service = new Drive.Builder(new NetHttpTransport(),
                GsonFactory.getDefaultInstance(),
                drive_token)
                .setApplicationName("Drive samples")
                .build();

        //create a new folder
        File fileMetadata = new File();
        fileMetadata.setName("image-output-0721-ShengWang");
        fileMetadata.setParents(Collections.singletonList(realFolderId));
        fileMetadata.setMimeType("application/vnd.google-apps.folder");
        try {
            File file = service.files().create(fileMetadata)
                    .setFields("id")
                    .execute();
            System.out.println("new folder id: "+file.getId());

            //success create a folder then upload the image
            //upload the paired images
            for(Pair<String, File> img_pair : imgs){

                File copy = new File();
                copy.setParents(Collections.singletonList(file.getId()));

                String out_name = img_pair.getKey()
                        .toLowerCase()
                        .replaceAll(" ", "-");
                copy.setName(out_name);
                try {
                    File resultFile = service.files().copy(img_pair.getValue().getId(), copy)
                            .setFields("id, parents")
                            .execute();
                    System.out.println(resultFile.getId());
                }catch (GoogleJsonResponseException e) {
                    System.err.println("Unable to copy file: " + e.getDetails());
                    throw e;
                }
            }
            System.out.printf("%d imgs uploaded\n", imgs.size());
            //upload all used img


        }catch (GoogleJsonResponseException e) {
            System.err.println("Unable to create folder: " + e.getDetails());
            throw e;
        }
    }

    //clear the folder onclude the previous result
    public void clear_folder(String folder_id) throws IOException {

        List<String> ids = new ArrayList<>();

        Drive service = new Drive.Builder(new NetHttpTransport(),
                GsonFactory.getDefaultInstance(),
                drive_token)
                .setApplicationName("Drive samples")
                .build();
        //item-picture-upload
        //mimeType != 'application/vnd.google-apps.folder'
        // Print the names and IDs for all files.
        FileList result = service.files().list()
                .setQ("'"+folder_id+"'"+" in parents")
                .setFields("nextPageToken, files(id, name)")
                .execute();
        List<File> files = result.getFiles();

        if (files == null || files.isEmpty()) {
            System.out.println("no previous result");
        } else {
            for (File file : files) {
                ids.add(file.getId());
            }
        }

        for(String id : ids){
            try {
                service.files().delete(id).execute();
                System.out.println("delet previous folder: "+id);
            } catch (IOException e) {
                System.out.println("An error occurred: " + e);
            }
        }

    }
}