(Java) Google Drive - Build a Local Cache of Metadata

This example demonstrates how to download the metadata for all files in a Google Drive account to create a local filesystem cache with the information. The cache can be used to fetch information without having to query Google Drive.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = true;

    // It requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example uses a previously obtained access token having permission for the 
    // Google Drive scope.

    CkAuthGoogle gAuth = new CkAuthGoogle();
    gAuth.put_AccessToken("GOOGLE_DRIVE_ACCESS_TOKEN");

    CkRest rest = new CkRest();

    // Connect using TLS.
    boolean bAutoReconnect = true;
    success = rest.Connect("www.googleapis.com",443,true,bAutoReconnect);

    // Provide the authentication credentials (i.e. the access token)
    rest.SetAuthGoogle(gAuth);

    // -------------------------------------------------------------------
    // Initialize our cache object.  Indicate the location of the root cache directory, and how many cache levels are to exist.
    // For small caches (level 0) all cache files are in the root directory.
    // For medium caches (level 1) cache files are located in 256 sub-directories from the root.
    // For large caches (level 2) cache files are located in 256x256 sub-directories two levels down from the root.
    CkCache gdCache = new CkCache();
    gdCache.put_Level(0);
    // Use a root directory that makes sense on your operating system..
    gdCache.AddRoot("C:/ckCache/googleDrive");

    // If we are re-building the cache, we can first delete the entire contents of the cache.
    int numCacheFilesDeleted = gdCache.DeleteAll();

    // Create a date/time object with an time 7 days from the current date/time.
    CkDateTime dtExpire = new CkDateTime();
    dtExpire.SetFromCurrentSystemTime();
    dtExpire.AddDays(7);

    // Indicate that we want ALL possible fields.
    // If no fields are indicated, then only the basic fields are returned.
    String allFields = "appProperties,capabilities,contentHints,createdTime,description,explicitlyTrashed,fileExtension,folderColorRgb,fullFileExtension,headRevisionId,iconLink,id,imageMediaMetadata,isAppAuthorized,kind,lastModifyingUser,md5Checksum,mimeType,modifiedByMeTime,modifiedTime,name,originalFilename,ownedByMe,owners,parents,permissions,properties,quotaBytesUsed,shared,sharedWithMeTime,sharingUser,size,spaces,starred,thumbnailLink,trashed,version,videoMediaMetadata,viewedByMe,viewedByMeTime,viewersCanCopyContent,webContentLink,webViewLink,writersCanShare";

    // We're going to keep a master list of fileId's as we iterate over all the files in this Google Drive account.
    // This master list will also be saved to the cache under the key "AllGoogleDriveFileIds".
    CkJsonObject jsonMaster = new CkJsonObject();
    CkJsonArray jsonMasterArr = jsonMaster.AppendArray("fileIds");
    // Also keep a list of file paths.
    CkJsonArray jsonMasterPaths = jsonMaster.AppendArray("filePaths");

    // The default page size is 100, with a max of 1000.
    rest.AddQueryParam("pageSize","200");

    CkJsonObject json = new CkJsonObject();
    CkJsonObject jsonFileMetadata;
    int i;
    int numFiles;

    // Send the request for the 1st page.
    String jsonResponse = rest.fullRequestNoBody("GET","/drive/v3/files");

    int pageNumber = 1;
    String pageToken;
    boolean bContinueLoop = rest.get_LastMethodSuccess() && (rest.get_ResponseStatusCode() == 200);

    while (bContinueLoop == true) {

        System.out.println("---- Page " + pageNumber + " ----");
        json.Load(jsonResponse);

        numFiles = json.SizeOfArray("files");
        i = 0;
        while (i < numFiles) {
            // Add this file ID to the master list.
            json.put_I(i);
            jsonMasterArr.AddStringAt(-1,json.stringOf("files[i].id"));

            i = i+1;
            }

        // Get the next page of files.
        // If the "nextPageToken" is present in the JSON response, then use it in the "pageToken" parameter
        // for the next request.   If no "nextPageToken" was present, then this was the last page of files.
        pageToken = json.stringOf("nextPageToken");
        bContinueLoop = false;
        boolean bHasMorePages = json.get_LastMethodSuccess();
        if (bHasMorePages == true) {
            rest.ClearAllQueryParams();
            rest.AddQueryParam("pageSize","200");
            rest.AddQueryParam("pageToken",pageToken);
            jsonResponse = rest.fullRequestNoBody("GET","/drive/v3/files");
            bContinueLoop = rest.get_LastMethodSuccess() && (rest.get_ResponseStatusCode() == 200);
            pageNumber = pageNumber+1;
            }

        }

    // Check to see if the above loop exited with errors...
    if (rest.get_LastMethodSuccess() != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    // Check to see if the above loop exited with errors...
    // A successful response will have a status code equal to 200.
    if (rest.get_ResponseStatusCode() != 200) {
        System.out.println("response status code = " + rest.get_ResponseStatusCode());
        System.out.println("response status text = " + rest.responseStatusText());
        System.out.println("response header: " + rest.responseHeader());
        System.out.println("response JSON: " + jsonResponse);
        return;
        }

    // Iterate over the file IDs and download the metadata for each, saving each to the cache...
    // Also, keep in-memory hash entries of the name and parent[0] so we can quickly 
    // build the path-->fileId cache entries. (Given that the Google Drive REST API uses
    // fileIds, this gives us an easy way to lookup a fileId based on a filePath.)
    CkHashtable hashTable = new CkHashtable();
    // Set the capacity of the hash table to something reasonable for the number of files
    // to be hashed.
    hashTable.ClearWithNewCapacity(521);

    CkStringBuilder sbPathForFileId = new CkStringBuilder();

    // Used for storing the file name and parents[0] in the hashTable.
    CkStringArray saFileInfo = new CkStringArray();
    saFileInfo.put_Unique(false);

    String fileId;
    numFiles = jsonMaster.SizeOfArray("fileIds");
    i = 0;
    while (i < numFiles) {
        jsonMaster.put_I(i);
        fileId = jsonMaster.stringOf("fileIds[i]");
        sbPathForFileId.SetString("/drive/v3/files/");
        sbPathForFileId.Append(fileId);

        rest.ClearAllQueryParams();
        rest.AddQueryParam("fields",allFields);
        jsonResponse = rest.fullRequestNoBody("GET",sbPathForFileId.getAsString());
        if ((rest.get_LastMethodSuccess() != true) || (rest.get_ResponseStatusCode() != 200)) {
            // Force an exit of this loop..
            numFiles = 0;
            }

        // Save this file's metadata to the local cache.
        // The lookup key is the fileId.
        gdCache.SaveTextDt(fileId,dtExpire,"",jsonResponse);

        // Get this file's name and parent[0], and put this information
        // in our in-memory hashtable to be used below..
        json.Load(jsonResponse);

        saFileInfo.Clear();
        saFileInfo.Append(json.stringOf("name"));
        saFileInfo.Append(json.stringOf("parents[0]"));
        hashTable.AddStr(fileId,saFileInfo.serialize());

        System.out.println(json.stringOf("name") + ", " + json.stringOf("parents[0]"));

        i = i+1;
        }

    // Check to see if the above loop exited with errors...
    if (rest.get_LastMethodSuccess() != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    // Check to see if the above loop exited with errors...
    // A successful response will have a status code equal to 200.
    if (rest.get_ResponseStatusCode() != 200) {
        System.out.println("response status code = " + rest.get_ResponseStatusCode());
        System.out.println("response status text = " + rest.responseStatusText());
        System.out.println("response header: " + rest.responseHeader());
        System.out.println("response JSON: " + jsonResponse);
        return;
        }

    // Now that all the fileId's are in the cache, let's build the directory path
    // for each fileID.  

    // (Technically, a fileId can have multiple parents, which means it can be in multiple directories
    // at once.  This is only going to build directory paths following the 0'th parent ID in the parents list.)

    // The directory path for files in "My Drive" will be just the filename.
    // For files in sub-directories, the path will be relative, such as "subdir1/subdir2/something.pdf"
    // 

    System.out.println("---- building paths ----");

    CkStringBuilder sbPath = new CkStringBuilder();
    numFiles = jsonMaster.SizeOfArray("fileIds");
    i = 0;
    while (i < numFiles) {
        jsonMaster.put_I(i);

        sbPath.Clear();

        fileId = jsonMaster.stringOf("fileIds[i]");
        boolean bFinished = false;
        while ((bFinished == false)) {
            saFileInfo.Clear();
            saFileInfo.AppendSerialized(hashTable.lookupStr(fileId));
            // Append this file or directory name.
            sbPath.Prepend(saFileInfo.getString(0));
            // Get the parent fileId
            fileId = saFileInfo.getString(1);
            // If this fileId is not in the hashtable, then it's the fileId for "My Drive", and we are finished.
            if (hashTable.Contains(fileId) == false) {
                bFinished = true;
                }
            else {
                sbPath.Prepend("/");
                }

            }

        System.out.println(i + ": " + sbPath.getAsString());

        // Store the filePath --> fileId mapping in our local cache.
        fileId = jsonMaster.stringOf("fileIds[i]");
        gdCache.SaveTextDt(sbPath.getAsString(),dtExpire,"",fileId);

        jsonMasterPaths.AddStringAt(-1,sbPath.getAsString());

        i = i+1;
        }

    // Save the master list of file IDs and file paths to the local cache.
    jsonMaster.put_EmitCompact(false);
    String strJsonMaster = jsonMaster.emit();
    gdCache.SaveTextNoExpire("AllGoogleDriveFileIds","",strJsonMaster);
    System.out.println("JSON Master Record:");
    System.out.println(strJsonMaster);

    // The JSON Master Cache Record looks something like this:
    // An application can load the JSON master record and iterate over all the files
    // in Google Drive by file ID, or by path.  
    // {
    //   "fileIds": [
    //     "0B53Q6OSTWYolQlExSlBQT1phZXM",
    //     "0B53Q6OSTWYolVHRPVkxtYWFtZkk",
    //     "0B53Q6OSTWYolRGZEV3ZGUTZfNFk",
    //     "0B53Q6OSTWYolS2FXSjliMXQxSU0",
    //     "0B53Q6OSTWYolZUhxckMzb0dRMzg",
    //     "0B53Q6OSTWYolbUF6WS1Gei1oalk",
    //     "0B53Q6OSTWYola296ODZUSm5GYU0",
    //     "0B53Q6OSTWYolbTE3c3J5RHBUcHM",
    //     "0B53Q6OSTWYolTmhybWJSUGd5Q2c",
    //     "0B53Q6OSTWYolY2tPU1BnYW02T2c",
    //     "0B53Q6OSTWYolTTBBR2NvUE81Zzg",
    //   ],
    //   "filePaths": [
    //     "testFolder/abc/123/pigs.json",
    //     "testFolder/starfish20.jpg",
    //     "testFolder/penguins2.jpg",
    //     "testFolder/starfish.jpg",
    //     "testFolder/abc/123/starfish.jpg",
    //     "testFolder/abc/123/penguins.jpg",
    //     "testFolder/abc/123",
    //     "testFolder/abc",
    //     "testFolder/testHello.txt",
    //     "testFolder",
    //     "helloWorld.txt",
    //   ]
    // }

    System.out.println("Entire cache rebuilt...");
  }
}