Session Types sample (Delphi)

Overview

This example shows the essence of sessions and various session managers usage:

• TROInMemorySessionManager
• TROOlympiaSessionManager
• TROEventSessionManager
• TRODBSessionManager

Prerequisites

Some parts of this sample require the following:

• Olympia Server to be running on the same computer with the sample server application
• MS SQL database server available on the same computer with the sample server application
• MS SQL server should have Northwind sample database installed and a custom table created in this database:

CREATE TABLE [dbo].[Sessions] (
    [SessionID] [char] (38) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL PRIMARY KEY,
    [Created] [datetime] NULL , [LastAccessed] [datetime] NULL ,
    [Data] [IMAGE] NULL )

Getting Started

• Build or compile all projects.
• Launch the server (via the menu option: Tools -> Remoting SDK -> Launch Server Executable).
• Activate the session manager option desired.
• Make sure required servers are up and running.
• Launch the client.
• Perform login with any UserID, Password should be equal to the login name.
• See the Session ID displayed after login.
• Check the session manager by clicking the Get button next to the Manager Name field.
• Input Name and Value then click Set Value button. The value will be stored in the session.
• Erase the content of the Value field then click Get Value button. The value will be read from the session and displayed back to the field.

Examine the Code

• Session storage is not accessible from client directly so we use a couple of methods of the service to get and set values (SessionTypesService_Impl.pas file):

function TSessionTypesService.GetSessionValue(const Name: Unicodestring): Unicodestring;
begin
  // ...
  result := VarToStr(Session.Values[Name]);
  // ...
end;

procedure TSessionTypesService.SetSessionValue(const Name: Unicodestring; const Value: Unicodestring);
begin
  // ...
  Session.Values[Name] := Value;
  // ...
end;

• Examine the simple login service implementation (LoginService_Impl.pas file). Accessing the Session property creates the session if it is not created yet, calling DestroySession destroys it. According to the protected services design guidelines the working service requires session to be created when this service is called (RequreSession property is set to true).

function TLoginService.Login(const UserID: Unicodestring; const Password: Unicodestring): boolean;
begin
  // ...
  result := (UserID <> '') and (UserID = Password); // Dummy test... You would code the one specific to your system
  if Result then begin
    Session.Values['Login'] := UserId;
    Session.Values['Password'] := Password;
    Log('Login successful');
  end
  else begin
    Log('Invalid login!');
    DestroySession; // Wrong login! The session cannot be persisted
  end;
end;

procedure TLoginService.Logout(const SessionID: Unicodestring);
var
  aUser: Unicodestring;
begin
  if Session.Values['Login'] <> Null then
    aUser := Session.Values['Login']
  else
    aUser := '';
  Log('User ''' + aUser + ''' has requested logout');
  Log('');
  DestroySession; // Removes the session from the SessionManager
end;

• Event session manager introduces a set of events fired in response to operations performed with the session manager (creating, destroying, expiring sessions etc.). You could handle these events and implement any session storage you like, examine the following event handlers:

procedure TSessionTypes_ServerMainForm.EventSessionManagerReleaseSession(
  var aSession: TROSession; NewSession: Boolean);
begin
  // ...
end;

function TSessionTypes_ServerMainForm.EventSessionManagerGetSessionCount(
  SessionManager: TROCustomSessionManager): Integer;
begin
  result := EventSessionList.Count;
end;


procedure TSessionTypes_ServerMainForm.EventSessionManagerDeleteSession(
  const aSessionID: TGUID; IsExpired: Boolean);
begin
  // ...
end;

procedure TSessionTypes_ServerMainForm.EventSessionManagerClearSessions(
  SessionManager: TROCustomSessionManager; OnlyExpired: Boolean);
begin
  // ...
end;

procedure TSessionTypes_ServerMainForm.EventSessionManagerFindSession(
  const aSessionID: TGUID; out aSession: TROSession);
begin
  // ...
end;

Data Abstract Users

This sample can easily be extended to encompass Data Abstract via the following steps:

• Create TDAConnectionManager, TDADriverManager, TDAADODriver and TDASchema instances.
• Relink.
• In the schema, create the datasets and commands similar to qu* (TADOQuery).
• Create a TDADBSessionManager instance and assign the corresponding datasets and commands.