Application Exception Writer Component

{
 Designer: Craig Ward, [[Email Removed]]
 Date:     19/11/95
 Version:  1.1

 Function: Writes application error messages to text-file.

 Fields:   There are two properties that the developer can set:

            [1] ErrorLog - a string that stores the full path and filename of
                           the text-file (this must be set)
            [2] UserName - a string that stores the application's current
                           user name (this does not need to be set)

 Calling:   There is only one method to call, and this must be passed the
            information that an exception will generate.

            For instance, in your application you will need to add the following
            line (it is probably best to add this line to the main form's unit,
            somewhere OnCreate):

              Application.OnException := AppException1.WriteException(Sender,E);

            This will write the error message to the text file specified in the
            TextFile field, adding user and dateTime details.

 Try....:   It is likely that there is try..except blocks within your application.
            If these blocks contain default handling of exceptions (for instance,
            you may abort or exit from a routine that attemtps to wrongly divide
            by zero) then your handler will execute, and the application's
            AppException component will be bypassed.
*******************************************************************************}
unit Appex;

interface

uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs;


type
  TAppException = class(TComponent)
  private
    { Private declarations }
    FTextFile: string;
    FUserName: string;
    procedure SetTextFile(value: string);
    procedure SetUserName(value: string);
  protected
    { Protected declarations }
  public
    { Public declarations }
    procedure WriteException(Sender: TObject; E: Exception);
  published
    { Published declarations }
    property ErrorLog: string read FTextFile write SetTextFile;
    property UserName: string read FUserName write SetUserName;
  end;

procedure Register;

{*******************************************************************************}
implementation

{register component}
procedure Register;
begin
  RegisterComponents('Samples', [TAppException]);
end;

{set text file}
procedure TAppException.SetTextFile(value: string);
begin
 if FTextFile <> value then
  FTextFile := value;
end;

{set user name}
procedure TAppException.SetUserName(value: string);
begin
 if FUserName <> value then
  FUserName := value;
end;

{write exception message to text file}
procedure TAppException.WriteException(Sender: TObject; E: Exception);
var
 tF: TextFile;
begin
 AssignFile(tF,FTextFile);                     {assign field to Text-File}
 Append(tF);                                   {prepare to append to file}

 if FUserName <> '' then
  WriteLn(tF,'User: '+FUserName);              {write user name - optional}

 WriteLn(tF,DateTimeToStr(Now));               {write time}

 WriteLn(tF,E.Message);                        {write error message}
 Writeln(tf,'');                               {add blank line}

 CloseFile(tF);                                {close file}

 application.ShowException(E);                 {show exception}

end;


end.