Working with HTTP Sessions

HTTP sessions provide a way to maintain state across multiple HTTP requests from the same client. The TCustomSession class manages session data using session IDs that are typically stored in cookies.

Sessions can be in different states: ssNew (newly created), ssActive (currently valid), ssExpired (timed out), or ssResponseInitialized (response has been started). Session variables are accessed using string key-value pairs through the Variables property.

program SessionExample;

{$mode objfpc}{$H+}

uses
  httpdefs, SysUtils, Classes;

type
  TMySession = class(TCustomSession)
  private
    FData: TStringList;
  protected
    function GetSessionVariable(const VarName: String): String; override;
    procedure SetSessionVariable(const VarName: String; const AValue: String); override;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  end;

constructor TMySession.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FData := TStringList.Create;
  TimeOutMinutes := 30; // 30 minutes timeout
end;

destructor TMySession.Destroy;
begin
  FData.Free;
  inherited Destroy;
end;

function TMySession.GetSessionVariable(const VarName: String): String;
var
  Index: Integer;
begin
  Index := FData.IndexOfName(VarName);
  if Index >= 0 then
    Result := FData.ValueFromIndex[Index]
  else
    Result := '';
end;

procedure TMySession.SetSessionVariable(const VarName: String; const AValue: String);
begin
  FData.Values[VarName] := AValue;
end;

var
  Session: TMySession;
begin
  Session := TMySession.Create(nil);
  try
    // Store session data
    Session.Variables['username'] := 'john_doe';
    Session.Variables['last_login'] := DateTimeToStr(Now);

    // Retrieve session data
    Writeln('Username: ', Session.Variables['username']);
    Writeln('Last login: ', Session.Variables['last_login']);

    Writeln('Session ID: ', Session.SessionID);
    Writeln('Session cookie: ', Session.SessionCookie);
  finally
    Session.Free;
  end;
end.