VG Midas library
[Overview] [Demos] [Components] [Function libs] [Changes] [Soon]



Overview
VG Midas Library is extension of VG VCL Library. Library includes a number of components for Midas multi-tier application development. It is compatible with Delphi 3 and 4 client/server editions.

VG Midas component set together with BDE Server application server provides a complex solution in development client/server application using Midas technology.

Library reqires VG VCL Library to be installed.

There are some classes in the library inherited from classes released in the RX library. These components are optional. To use them you should have RX library 2.50 or higher to be installed.

There is April, 1999 release of VG Midas Library.

Demos
\Demos\DB\MastApp standart demo project have been ported into real multi-tier during 40 minutes! You can download it's compiled version with full source here.

Components

[Mulitier]

  • TProviderList component manages list of run-time created providers. Component working with conjunction with TvgRemoteDataModule makes list of providers available for client applications trough IvgRemoteDataModule interface without reqiring to publish each provider as property while designing server module.
  • TProviderFactory hooks data packets exchange between remote server and client datasets. It allows to centralize both on client and server implementation of user-defined operations on data packets which realize data crypting and/or compression.
  • TvgClientDataSet component is TClientDataSet descendent. It implements support for parameters and macroses (see TRxQuery) both for Delphi 3 and Delphi 4 and is compatible with TvgProvider and TRxQuery on server side. Component also implements enhanced sorting functionality that allows you to sort both in ascending and descending orders.
  • TClientDataSetHook is TDataSetHook descendent that hooks TClientDataSet events to make them defined only one time within application (see TBDEDataSetHook).
  • TSinglePointServer is remote server component descended from TvgRemoteServer (see below) that implements single-point connection. In conjunction with TvgRemoteDataModule it implements internal OLE automation server and allows to create multi-tier applications in single-point mode.
  • TvgCustomRemoteServer and it descendents TvgRemoteServer, TvgCORBARemoteServer provide an additional way of abstraction in using remote server components. TvgCustomRemoteServer "hooks" real remote server component and hides (Delphi 4) it's implementation (COM or CORBA) under number of virtual method and properties. TvgCustomRemoteServer provides support for BDE Server interface. It supports TProviderFactory (see above) and allows to automatically loggon onto remote servers.
  • TvgSocketConnection is advanced remote server components that implements thread-safe socket remote server. It allows you to make calls to the COM server from different threads without care about critical sections. Also it fixes a number of bugs of original TMidasConnection and TSocketConnection components. Also it supports datablock interception for Delphi 4 like Delphi 4 TSocketConnection does.
  • TvgSocketDispatcher is enhanced TSocketDispatcher that provides events for custom interception of datablocks. TvgSocketDispatcher supports timeouts for inactive connections.
  • TDatabaseProvider is server-side portion of IDatabase interface that incapsulates TDatabase functionality. It supports remote transaction control, alias connectivity and autocreation of providers by client request.

    BDE Server client components
    BDE Server client components in conjuntion with BDE Server application implements the newest Midas-based BDE replacement. Components allows you to work with same properties, methods, error codes and even property editors as their BDE prototypes has but doesn't reqire BDE to be installed.

    Client components client components support aliases, databases, transactions, tables, queries, stored procedures, update SQL statements, cached updates and BDE error codes.

    With BDE Server and VG Midas you can easy create new or port old applications within distributed architecture that will be powered with both BDE functionality and Midas flexibility.

  • TvgClientDatabase incapsulates client-side functionality of TDatabase component. TvgClientDatabase allows to use TvgClientTable, TvgClientQuery and TvgClientStoredProc at client side. Component controls remote database connection, transaction control and manages the list of connected TvgClientBDEDataSets.
  • TvgClientTable implements client-side TTable analog that allows to open remote tables.
  • TvgClientQuery implements client-side TQuery analog. It allows to open or execute SQL statement in the same way as TQuery does. Component supports SQL, Params and Macros properties (see TRxQuery).
  • TvgClientStoredProc is client-side TStoredProc analog that allows to open or execute remote stored procedures.
  • TvgClientUpdateSQL is TUpdateSQL analog. This is a helper object that is used by TvgClientBDEDataSet to implement client-side cached updates mechanism and apply updates into remote server. It has the same properties as TUpdateSQL. TvgClientUpdateSQL also supports macroses in update statements.
  • TvgClientBatchMove is full-functional TBatchMove analog. TvgClientBatchMove extends functionality of their prototype and supports any TDataSet descendent as it's source dataset.
  • TvgClientSQLScript component allows execution of multiple SQL statements in one query. Component supports parameters and macroses.
  • TvgClientUpdateScript is another update object. It executes multiple SQL statements for update purposes. Component supports parameters and macroses.

    Function libraries

    • vgCDSUtl.pas - client dataset utility routines
    • vgSock.pas - WinSock utility routines

    Changes

    Changes list

    Soon