Work with Google Cloud Storage Data in FoxPro

The CData ODBC Driver for Google Cloud Storage enables you to access Google Cloud Storage data using the ODBC standard. You can use the CData ODBC Driver for Google Cloud Storage to integrate Google Cloud Storage data into your FoxPro project. The procedure below provides a walk-through of the included code sample, which saves Google Cloud Storage data into tables in a FoxPro database.

Connect to Google Cloud Storage as an ODBC Data Source

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

NOTE: Set the 'Map To WVarchar' connection property to FALSE (FoxPro uses the ODBC W API and returns the WCHAR for the value type).

Authenticate with a User Account

You can connect without setting any connection properties for your user credentials. After setting InitiateOAuth to GETANDREFRESH, you are ready to connect.

When you connect, the Google Cloud Storage OAuth endpoint opens in your default browser. Log in and grant permissions, then the OAuth process completes

Authenticate with a Service Account

Service accounts have silent authentication, without user authentication in the browser. You can also use a service account to delegate enterprise-wide access scopes.

You need to create an OAuth application in this flow. See the Help documentation for more information. After setting the following connection properties, you are ready to connect:

• InitiateOAuth: Set this to GETANDREFRESH.
• OAuthJWTCertType: Set this to "PFXFILE".
• OAuthJWTCert: Set this to the path to the .p12 file you generated.
• OAuthJWTCertPassword: Set this to the password of the .p12 file.
• OAuthJWTCertSubject: Set this to "*" to pick the first certificate in the certificate store.
• OAuthJWTIssuer: In the service accounts section, click Manage Service Accounts and set this field to the email address displayed in the service account Id field.
• OAuthJWTSubject: Set this to your enterprise Id if your subject type is set to "enterprise" or your app user Id if your subject type is set to "user".
• ProjectId: Set this to the Id of the project you want to connect to.

The OAuth flow for a service account then completes.

Connect and Transfer

To get started, add the code sample to a new project. You can execute the following command to save all tables without displaying them:

Below is the process that the program follows:

1. Create a new FoxPro database.

2. Open a connection to Google Cloud Storage data with the line below:

   m.hSQLconnection = SQLCONNECT(m.cODBCDSN)

3. If the connection was successful, you can now retrieve the list of tables using the SQLTABLES function. The code below saves the list of tables in sys_tables.dbf:

   WAIT WINDOW "Fetching tables for data source '" + m.cODBCDSN + "'..." NOWAIT NOCLEAR m.nSQLTABLES = SQLTABLES(m.hSQLconnection) IF lUseDistinctConnections WAIT WINDOW "Closing ODBC Connection for data source '" + m.cODBCDSN + "'..." NOWAIT NOCLEAR SQLDISCONNECT(m.hSQLconnection) m.hSQLconnection = 0 * SQLCONNECT needs to be called again ENDIF IF m.nSQLTABLES > 0 * create local table containing list of tables in db COPY TO (m.cImportData + "sys_tables") USE * convert each table to DBF USE (m.cImportData + "sys_tables") ALTER TABLE DBF("sys_tables") ; ADD COLUMN records i ; ADD COLUMN dbfname m
4. Scan over each table, saving it to a DBF file. The function ODBCtoDBF stores the table in a DBF file and then opens a grid if the lBrowse parameter is set to true: FUNCTION ODBCtoDBF (cTableName as String, cTableType as String, lBrowse as Logical, lhSQLConnection as Integer) WAIT WINDOW ; "Converting " + m.cTableType + ' "' + m.cTableName + '" to DBF...' ; NOWAIT NOCLEAR ACTIVATE SCREEN * strip characters incompatible with FoxPro out of the name of the DBF file m.cTableAlias = "" m.nTableNameLen = LEN(m.cTableName) m.nTableNameStart = 1 FOR m.nTableNameStart = 1 TO m.nTableNameLen m.cCharacter = SUBSTR(m.cTableName, m.nTableNameStart, 1) IF !ISALPHA(m.cCharacter) .and. (m.nTableNameStart = 1 .or. !ISDIGIT(m.cCharacter)) m.cTableAlias = m.cTableAlias + "_" ELSE m.cTableAlias = m.cTableAlias + m.cCharacter ENDIF ENDFOR m.cFromTable = m.cTableName m.cTempViewAlias = m.cTableType + "_" + m.cTableAlias LOCAL loException as Exception LOCAL lnResultSets TRY * run query m.lnResultSets = SQLEXEC(m.lhSQLConnection, ; "SELECT * FROM " + m.cFromTable, ; m.cTempViewAlias, ; aSQLResult) IF m.lnResultSets#1 SET STEP ON ENDIF ACTIVATE SCREEN CATCH TO m.loException ACTIVATE SCREEN ? "Error opening " + m.cTempViewAlias + ":" ? m.loException.Message ? m.loException.Details ENDTRY IF !USED(m.cTempViewAlias) RETURN ENDIF * copy records from view cursor to disk SELECT * FROM (m.cTempViewAlias) ; INTO TABLE (m.cImportData + m.cTableAlias) IF USED(m.cTableAlias) ACTIVATE SCREEN FLUSH && flush the buffer to write the data to disk IF m.lBrowse * pop the table up on screen SELECT (m.cTableAlias) BROWSE NORMAL NOMODIFY NOWAIT ACTIVATE SCREEN ELSE * close on-disk table for now USE IN (m.cTableAlias) ACTIVATE SCREEN ENDIF ENDIF IF USED(m.cTempViewAlias) USE IN &cTempViewAlias && close SQL view ACTIVATE SCREEN ENDIF WAIT CLEAR ENDFUNC
5. You can now save tables of Google Cloud Storage data as DBF files.

Below is the full code, in FoxPro 9 syntax: