The Client Project (Delphi)

Overview

The client project that is generated by the new Data Abstract Project Wizard is a rather simple application. It is intentionally created to be as simple as possible, because it is supposed to be only a starting point for developing a new application that allows to skip some routine work in the very beginning of the application development cycle.

Project Contents

Project Overview

This article describes the VCL client application project. The FMX client application will have other components (for example TDAFMXReconcileProvider instead of TDAVCLReconcileProvider), but DataModule and Data Definition will always remain the very core of the application.

A newly generated client application contains several files:

File	Description
fClientDataModule.pas	Data Module: Contains all components responsible for communication with a remote server.
fLogOnForm.pas	(Optional) Log On dialog definition
fClientForm.pas	Main Application Form

All components are described below in more detail.

DataModule

This form contains the following sub-components:

Sub-component	Description
ClientChannel	The Client Channel performs low-level communication with the server. The Client Channel also handles the OnLoginNeeded event raised when a remote server requests user authentication by calling the LogOn method (see below).
Message	The Message component performs protocol-specific data serialization and deserialization.
EncryptionEnvelope	The (optional) AES Encryption Envelope component encrypts data sent over the wire.
RemoteDataAdapter	The Data Adapter component is the core element that sends data requests to the server.
RemoteService	This component receives data requests from the RemoteDataAdapter instance and sends them to the remote server using ClientChannel and Message.
DataStreamer	The Data Streamer serializes and deserializes data requests.

These components are created for each table:

Prefix	Description
sp_tbl_	Optional Business Rules Scripting support component
tbl_	Data Tables component
ds_	Data Source component, used for linking visual components like TDBGrid with Data Tables components

Please note that some components (f.e. EncryptionEnvelope) are optional and are added to the generated Data Module only when the appropriate options were selected in the Project Wizard.

The Data Module exposes the following properties and methods:

Name	Kind	Description
fIsLoggedOn	property	This property returns true when logging on to the server was successful.
fUserId	property	This property gets the user name.
LogOn	method	This method performs the logging on to the server using the provided username and password, and returns true on success.
LogOff	method	This method performs the logging off from the server.

LogOn form

An optional dialog that asks for the user name and password and saves them to the application settings file. Please note that the password is saved as plain text without any encryption.

Main Form

Main application form. The Project Wizard leaves to it to the user to fill it with the needed content and application logic.

Summary

The client project generated by the New Project Wizard is a rather simple application. It is a good starting point for learning Data Abstract for Delphi or creating simple utility applications. However, more complex production-level applications would require major changes in the application (for example, the Data Module might be moved into a separate Data Access Layer assembly, the Log On dialog reworked to match the company style etc).