What is Midas in DELPHI? What is the related components? MiDAS (Multitiered Distribute Application Services) Multi-layer distributed application service Delphi's multi-tier structure is the original Two-Tier front desk application DBEXPRESS , ADO, BDE, SQL LINK, DATAMOULE, get another NT server (that is, the so-called application server), and only one left
The DataMoule moved to the NT server is moved to the NT server. Note: The front desk must publish MIDAS.DLL to the system directory. (1) The front desk will pass Call the application server provided by the application server (interface) proposes a request application server to respond to this request, transfer a corresponding SQL command to the background database, and the background database returns the DataSet generated by the SQL command to the application server. Note: Delphi provides Type Library to help the application server definition COM method (interface) (interface) (2) The COM program on the NT server is transmitted through the intermediate software (DBEXPRESS, ADO, BDE, SQL Link). SQL to the background database. When the application server is When transmitting the read DataSet to the front desk, you must use the DCOM mechanism to make the TDATASETPROVIDER component provided by DCOM to compress the read DataSet and split into a piece of data package.
Passing DCOM or TCP / IP to the front desk. Note: Delphi provides the RemoteDataModule wizard to help you generate a COM program. Since Delphi has a special mechanism for transmitting DataSet, Delphi also implements an interface called iProvider (ie tdatasetProvider) To help the COM program on the application server sends DataSet data. (3) The COM program on the front program and the NT server is to communicate with each other through the MIDAS.DLL and the application server communicate with each other through the Midas.dll and the application server. Midas.dll will restore the received application server to DataSet, throw the TclientDataSet components in the front program. Note: The front program must provide the corresponding TClientData component to each of the application server. IProvider (ie tdatasetProvider) corresponds to. When the user modifies the front desk data, the modified only cache is at the front desk Dataset, and finally
To write the data of the front desk back to the background database through the TclientData.ApplyUpdate method.
