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(Delphi ActiveX) Google Drive - Build a Local Cache of MetadataThis 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. Note: This example requires Chilkat v11.0.0 or greater.
uses Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB; ... procedure TForm1.Button1Click(Sender: TObject); var success: Integer; gAuth: TChilkatAuthGoogle; rest: TChilkatRest; bAutoReconnect: Integer; gdCache: TChilkatCache; numCacheFilesDeleted: Integer; dtExpire: TCkDateTime; allFields: WideString; jsonMaster: TChilkatJsonObject; jsonMasterArr: TChilkatJsonArray; jsonMasterPaths: TChilkatJsonArray; json: TChilkatJsonObject; jsonFileMetadata: IChilkatJsonObject; i: Integer; numFiles: Integer; jsonResponse: WideString; pageNumber: Integer; pageToken: WideString; bContinueLoop: Integer; bHasMorePages: Integer; hashTable: TChilkatHashtable; sbPathForFileId: TChilkatStringBuilder; saFileInfo: TCkStringArray; fileId: WideString; sbPath: TChilkatStringBuilder; bFinished: Integer; strJsonMaster: WideString; begin success := 0; success := 1; // 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. gAuth := TChilkatAuthGoogle.Create(Self); gAuth.AccessToken := 'GOOGLE_DRIVE_ACCESS_TOKEN'; rest := TChilkatRest.Create(Self); // Connect using TLS. bAutoReconnect := 1; success := rest.Connect('www.googleapis.com',443,1,bAutoReconnect); // Provide the authentication credentials (i.e. the access token) rest.SetAuthGoogle(gAuth.ControlInterface); // ------------------------------------------------------------------- // 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. gdCache := TChilkatCache.Create(Self); gdCache.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. numCacheFilesDeleted := gdCache.DeleteAll(); // Create a date/time object with an time 7 days from the current date/time. dtExpire := TCkDateTime.Create(Self); dtExpire.SetFromCurrentSystemTime(); dtExpire.AddDays(7); // Indicate that we want ALL possible fields. // If no fields are indicated, then only the basic fields are returned. 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". jsonMaster := TChilkatJsonObject.Create(Self); jsonMasterArr := TChilkatJsonArray.Create(Self); jsonMaster.AppendArray2('fileIds',jsonMasterArr.ControlInterface); // Also keep a list of file paths. jsonMasterPaths := TChilkatJsonArray.Create(Self); jsonMaster.AppendArray2('filePaths',jsonMasterPaths.ControlInterface); // The default page size is 100, with a max of 1000. rest.AddQueryParam('pageSize','200'); json := TChilkatJsonObject.Create(Self); // Send the request for the 1st page. jsonResponse := rest.FullRequestNoBody('GET','/drive/v3/files'); pageNumber := 1; bContinueLoop := rest.LastMethodSuccess and (rest.ResponseStatusCode = 200); while bContinueLoop = 1 do begin Memo1.Lines.Add('---- Page ' + IntToStr(pageNumber) + ' ----'); json.Load(jsonResponse); numFiles := json.SizeOfArray('files'); i := 0; while i < numFiles do begin // Add this file ID to the master list. json.I := i; jsonMasterArr.AddStringAt(-1,json.StringOf('files[i].id')); i := i + 1; end; // 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 := 0; bHasMorePages := json.LastMethodSuccess; if (bHasMorePages = 1) then begin rest.ClearAllQueryParams(); rest.AddQueryParam('pageSize','200'); rest.AddQueryParam('pageToken',pageToken); jsonResponse := rest.FullRequestNoBody('GET','/drive/v3/files'); bContinueLoop := rest.LastMethodSuccess and (rest.ResponseStatusCode = 200); pageNumber := pageNumber + 1; end; end; // Check to see if the above loop exited with errors... if (rest.LastMethodSuccess = 0) then begin Memo1.Lines.Add(rest.LastErrorText); Exit; end; // Check to see if the above loop exited with errors... // A successful response will have a status code equal to 200. if (rest.ResponseStatusCode <> 200) then begin Memo1.Lines.Add('response status code = ' + IntToStr(rest.ResponseStatusCode)); Memo1.Lines.Add('response status text = ' + rest.ResponseStatusText); Memo1.Lines.Add('response header: ' + rest.ResponseHeader); Memo1.Lines.Add('response JSON: ' + jsonResponse); Exit; end; // 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.) hashTable := TChilkatHashtable.Create(Self); // Set the capacity of the hash table to something reasonable for the number of files // to be hashed. hashTable.ClearWithNewCapacity(521); sbPathForFileId := TChilkatStringBuilder.Create(Self); // Used for storing the file name and parents[0] in the hashTable. saFileInfo := TCkStringArray.Create(Self); saFileInfo.Unique := 0; numFiles := jsonMaster.SizeOfArray('fileIds'); i := 0; while i < numFiles do begin jsonMaster.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.LastMethodSuccess <> 1) or (rest.ResponseStatusCode <> 200)) then begin // Force an exit of this loop.. numFiles := 0; end; // Save this file's metadata to the local cache. // The lookup key is the fileId. gdCache.SaveTextDt(fileId,dtExpire.ControlInterface,'',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()); Memo1.Lines.Add(json.StringOf('name') + ', ' + json.StringOf('parents[0]')); i := i + 1; end; // Check to see if the above loop exited with errors... if (rest.LastMethodSuccess = 0) then begin Memo1.Lines.Add(rest.LastErrorText); Exit; end; // Check to see if the above loop exited with errors... // A successful response will have a status code equal to 200. if (rest.ResponseStatusCode <> 200) then begin Memo1.Lines.Add('response status code = ' + IntToStr(rest.ResponseStatusCode)); Memo1.Lines.Add('response status text = ' + rest.ResponseStatusText); Memo1.Lines.Add('response header: ' + rest.ResponseHeader); Memo1.Lines.Add('response JSON: ' + jsonResponse); Exit; end; // 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" // Memo1.Lines.Add('---- building paths ----'); sbPath := TChilkatStringBuilder.Create(Self); numFiles := jsonMaster.SizeOfArray('fileIds'); i := 0; while i < numFiles do begin jsonMaster.I := i; sbPath.Clear(); fileId := jsonMaster.StringOf('fileIds[i]'); bFinished := 0; while (bFinished = 0) do begin 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) = 0) then begin bFinished := 1; end else begin sbPath.Prepend('/'); end; end; Memo1.Lines.Add(IntToStr(i) + ': ' + sbPath.GetAsString()); // Store the filePath --> fileId mapping in our local cache. fileId := jsonMaster.StringOf('fileIds[i]'); gdCache.SaveTextDt(sbPath.GetAsString(),dtExpire.ControlInterface,'',fileId); jsonMasterPaths.AddStringAt(-1,sbPath.GetAsString()); i := i + 1; end; // Save the master list of file IDs and file paths to the local cache. jsonMaster.EmitCompact := 0; strJsonMaster := jsonMaster.Emit(); gdCache.SaveTextNoExpire('AllGoogleDriveFileIds','',strJsonMaster); Memo1.Lines.Add('JSON Master Record:'); Memo1.Lines.Add(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", // ] // } Memo1.Lines.Add('Entire cache rebuilt...'); end; |
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