OLE DB Provider Development - Encapsulating a Service Provider
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"OLE DB provider development" refers to the process of creating a software component, called an OLE DB provider, which enables applications to access data from a specific data source by implementing the OLE DB standard interfaces
![class CAgentMan
{
public:
TCHAR szCommand[256];
TCHAR szText[256];
BEGIN_PROVIDER_COLUMN_MAP(CAgentMan)
PROVIDER_COLUMN_ENTRY(“Field1”, 1, szCommand)
PROVIDER_COLUMN_ENTRY(“Field2”, 2, szText)
END_PROVIDER_COLUMN_MAP()
};
MODIFY DATA STRUCTURE
• Represents one row of data
• Contains data members and meta-data](https://image.slidesharecdn.com/oledbproviderdevelopment-250311023935-8d2766a9/85/OLE-DB-Provider-Development-Encapsulating-a-Service-Provider-25-320.jpg)
OLE DB Provider Development - Encapsulating a Service Provider
- 1. OLE DB PROVIDER DEVELOPMENT Arun Seetharaman Computer Call January 20, 1999
- 2. AGENDA • Universal Data Access • What is an OLE DB provider? • Creating an OLE DB provider with the OLE DB Provider Templates • Extending the provider • Questions and answers
- 4. WHAT IS AN OLE DB DATA PROVIDER? • Implements core OLE DB interfaces • Common interfaces to native functionality • Does not require data to look like a relational database • Implements extended OLE DB interfaces to expose native extended functionality
- 5. SCENARIOS • Relational Data • ODBC Driver exists, No OLE DB Provider • You App uses ADO to talk to OLE DB Provider for ODBC , which talks to the ODBC driver ◆ Relational Data ⚫ OLE DB Provider exists ⚫ You App uses ADO to talk to OLE DB Provider
- 6. SCENARIOS • Data in Exchange Server • OLE DB Provider exists, No Query Engine • You App uses ADO to talk to MS Exchange OLE DB Provider, calls upon a Query Processor component to handle querying ◆ Data in NT File System ⚫ OLE DB Provider over Microsoft Index Server ⚫ You App uses ADO to talk to OLE DB Provider
- 7. WHY WRITE A PROVIDER? • To participate in Universal Data Access: ⚫ Take advantage of ADO to provide C/C++, Java , Visual Basic®, IIS and OLE Automation programmers easy access to your data ⚫ Expose your data to SQL Server , Access, Excel, and third-party consumers ⚫ Add power to your data through common Query Processor, Cursor, Notification, and Remoting components ⚫ Participate in heterogeneous joins
- 8. PROVIDER TEMPLATE SUPPORT • You could implement a bunch of interfaces • OLE DB Provider Templates • Implements 20 of the most common OLE DB interfaces • New option in ATL Object Wizard • Minimal providers ready to go in ten minutes
- 9. PROVIDER TEMPLATE SUPPORT • Implements data source, session, command, and rowset objects • Implements all mandatory interfaces • Minimal case: • Developer changes PROVIDER_COLUMN_MAP and Execute() • Significant case: • Developer adds in additional objects and interfaces
- 10. CreateSession() Session IDBCreateCommand IOpenRowset Execute() Rowset Rowset OpenRowset() Command ICommand CreateCommand() OLE DB PROVIDER STRUCTURE Data Source IDBCreateSession
- 11. PROPERTIES • Can be set Objectwise • Defines Object specific behaviour • Type, Value, Read/Write attribute • Property Sets • Properties with the same GUID • Many are Pre-defined in OLEDB • Provider can define custom properties
- 12. GUID : PropertySet A Count: 3 Pointer : DBPROPSET Array ID: Property 1 Value : Value1 ID: Property 2 Value : Value2 ID: Property 1 Value : Value1 GUID : PropertySet A Count: 3 Pointer : DBPROPIDSET Array Property 1 Property 2 Property 3 DBPROPID Arrays
- 13. DATA SOURCE INTERFACES • IDBProperties • Sets properties used in initialization • Returns information about provider's capabilities • Data Source Properties Data Source Name, Version, Threading Model • Initialization Properties User ID, Password, Locale ID, Timeout
- 14. DATA SOURCE INTERFACES • IDBInitialize • Connects to the provider • State Change to ‘Initialized’ ◆ IDBCreateSession ⚫ Gets a session object ◆ IPersist ⚫ Returns your CLSID ⚫ To persist Connection Information
- 15. SESSION INTERFACES • IGetDataSource • Returns parent datasource • ISessionProperties • Sets properties on session Transaction Isolation Levels Supported in Auto-Commit Mode
- 16. SESSION INTERFACES • IOpenRowset • To Work directly with Table • No overhead of Query Language support ◆ IDBCreateCommand (Optional) ⚫ Only if you support commands
- 17. COMMAND INTERFACES • ICommandProperties • Set properties for open rowset ◆ ICommandText ⚫ Set and execute command
- 18. COMMAND INTERFACES • IAccessor • Defines how parameters are read • Binds each column or parameter to Consumer’s buffer ◆ IColumnsInfo ⚫ Provides metadata about Columns
- 19. ROWSET OBJECT People Name Address Papers Picture Voice David Mike Monica NY CA DC ... IStream IRowset IDraw IPlay
- 20. ROWSET OBJECT • Universal abstraction for tabular data • Base data, query results, computed data, schema… ◆ Rows can contain COM objects ◆ Efficient, streamlined access to large objects
- 21. ROWSET OBJECT • Rowset data can be shared ⚫ Multiple Consumers ⚫ Multiple Components ⚫ Notifications ⚫ Deferred/Immediate Updates
- 22. ROWSET INTERFACES • IColumnsInfo • Describes the columns of the rowset ◆ IAccessor ⚫ Defines how consumer reads data ◆ IRowsetInfo ⚫ Returns rowset properties Updatability, Bookmarks ... ⚫ Interface Support Find, Conversions ...
- 23. ROWSET INTERFACES • IRowset • GetNextRows retrieves row handles • GetData reads data from row handles ◆ IConvertType ⚫ Use the Data Conversion library
- 24. CREATING AN OLE DB PROVIDER • Run the OLE DB Provider Wizard • Generates COM objects for data source, session, command, and rowset • Modify and extend code
- 25. class CAgentMan { public: TCHAR szCommand[256]; TCHAR szText[256]; BEGIN_PROVIDER_COLUMN_MAP(CAgentMan) PROVIDER_COLUMN_ENTRY(“Field1”, 1, szCommand) PROVIDER_COLUMN_ENTRY(“Field2”, 2, szText) END_PROVIDER_COLUMN_MAP() }; MODIFY DATA STRUCTURE • Represents one row of data • Contains data members and meta-data
- 26. HRESULT Execute(DBPARAMS * pParams, LONG* pcRowsAffected) { ... } MODIFY EXECUTE IN ROWSET • Command is stored in m_strCommandText • Create instances of your data structure • Place instances in m_rgRowData • Set pcRowsAffected
- 27. DEMO • Creating a minimal provider • Run Provider Wizard • Modify data structure • Modify PROVIDER_COLUMN_MAP • Modify Execute()
- 28. EXTENDING THE PROVIDER • Schema rowsets • Properties • Add in validation routines • Add additional OLE DB interfaces
- 29. CONFORMANCE TESTS • Generic OLE DB tests that: • Verify conformance to minimum level • Test correctness of exposed interfaces • Based on sample test suites in OLE DB SDK • Provide a performance benchmark • Include ADO acceptance tests
- 30. SUMMARY • Writing a provider gives you… • C/C++, OLE Automation, Java, and scripting access to your data through ADO • Exposure to Microsoft® and third-party tools, products, and components