Pascal (Lazarus/Delphi)
Pascal (Lazarus/Delphi)
Google Drive - Build a Local Cache of Metadata
See more Google Drive Examples
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.Chilkat Pascal (Lazarus/Delphi) Downloads
program ChilkatDemo;
// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.
{$IFDEF FPC}
{$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}
uses
{$IFDEF UNIX}
cthreads,
{$ENDIF}
SysUtils,
CkDllLoader,
Chilkat.AuthGoogle,
Chilkat.CkDateTime,
Chilkat.JsonArray,
Chilkat.StringArray,
Chilkat.Rest,
Chilkat.JsonObject,
Chilkat.StringBuilder,
Chilkat.Cache,
Chilkat.Hashtable;
// ---------------------------------------------------------------------------
procedure RunDemo;
var
success: Boolean;
gAuth: TAuthGoogle;
rest: TRest;
bAutoReconnect: Boolean;
gdCache: TCache;
numCacheFilesDeleted: Integer;
dtExpire: TCkDateTime;
allFields: string;
jsonMaster: TJsonObject;
jsonMasterArr: TJsonArray;
jsonMasterPaths: TJsonArray;
json: TJsonObject;
jsonFileMetadata: TJsonObject;
i: Integer;
numFiles: Integer;
jsonResponse: string;
pageNumber: Integer;
pageToken: string;
bContinueLoop: Boolean;
bHasMorePages: Boolean;
hashTable: THashtable;
sbPathForFileId: TStringBuilder;
saFileInfo: TStringArray;
fileId: string;
sbPath: TStringBuilder;
bFinished: Boolean;
strJsonMaster: string;
begin
success := False;
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.
gAuth := TAuthGoogle.Create;
gAuth.AccessToken := 'GOOGLE_DRIVE_ACCESS_TOKEN';
rest := TRest.Create;
// Connect using TLS.
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.
gdCache := TCache.Create;
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;
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 := TJsonObject.Create;
jsonMasterArr := TJsonArray.Create;
jsonMaster.AppendArray2('fileIds',jsonMasterArr);
// Also keep a list of file paths.
jsonMasterPaths := TJsonArray.Create;
jsonMaster.AppendArray2('filePaths',jsonMasterPaths);
// The default page size is 100, with a max of 1000.
rest.AddQueryParam('pageSize','200');
json := TJsonObject.Create;
// 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 = True do
begin
WriteLn('---- Page ' + 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 := False;
bHasMorePages := json.LastMethodSuccess;
if (bHasMorePages = True) 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 = False) then
begin
WriteLn(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
WriteLn('response status code = ' + rest.ResponseStatusCode);
WriteLn('response status text = ' + rest.ResponseStatusText);
WriteLn('response header: ' + rest.ResponseHeader);
WriteLn('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 := THashtable.Create;
// Set the capacity of the hash table to something reasonable for the number of files
// to be hashed.
hashTable.ClearWithNewCapacity(521);
sbPathForFileId := TStringBuilder.Create;
// Used for storing the file name and parents[0] in the hashTable.
saFileInfo := TStringArray.Create;
saFileInfo.Unique := False;
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 <> True) 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,'',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());
WriteLn(json.StringOf('name') + ', ' + json.StringOf('parents[0]'));
i := i + 1;
end;
// Check to see if the above loop exited with errors...
if (rest.LastMethodSuccess = False) then
begin
WriteLn(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
WriteLn('response status code = ' + rest.ResponseStatusCode);
WriteLn('response status text = ' + rest.ResponseStatusText);
WriteLn('response header: ' + rest.ResponseHeader);
WriteLn('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"
//
WriteLn('---- building paths ----');
sbPath := TStringBuilder.Create;
numFiles := jsonMaster.SizeOfArray('fileIds');
i := 0;
while i < numFiles do
begin
jsonMaster.I := i;
sbPath.Clear();
fileId := jsonMaster.StringOf('fileIds[i]');
bFinished := False;
while (bFinished = False) 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) = False) then
begin
bFinished := True;
end
else
begin
sbPath.Prepend('/');
end;
end;
WriteLn(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;
end;
// Save the master list of file IDs and file paths to the local cache.
jsonMaster.EmitCompact := False;
strJsonMaster := jsonMaster.Emit();
gdCache.SaveTextNoExpire('AllGoogleDriveFileIds','',strJsonMaster);
WriteLn('JSON Master Record:');
WriteLn(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",
// ]
// }
WriteLn('Entire cache rebuilt...');
gAuth.Free;
rest.Free;
gdCache.Free;
dtExpire.Free;
jsonMaster.Free;
jsonMasterArr.Free;
jsonMasterPaths.Free;
json.Free;
hashTable.Free;
sbPathForFileId.Free;
saFileInfo.Free;
sbPath.Free;
end;
// ---------------------------------------------------------------------------
begin
try
RunDemo;
except
on E: Exception do
WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
end;
WriteLn;
{$IFDEF MSWINDOWS}
WriteLn('Press Enter to exit...');
ReadLn;
{$ENDIF}
end.