Indy 10 线程池使用范例

Indy 10有一个组件叫IdSchedulerOfThreadPool，网上没有其相关使用代码，好在有源代码，于是自己看。其实用起来也还比较简单，主要是实现了维护一个线程池的功能，功能不是很强。不过基于该组件的开发，也可以为我们省了不少代码，增强了些功能。

与该线程池使用相关的类主要有：
TIdSchedulerOfThreadPool 这个不用说
TIdTask(in IdTask.pas) 需要用户继承实现的类，实现参数的传入，及具体的run、BeforeRun、AfterRun功能代码
TIdYarnOfThread(in IdSchedulerOfThread.pas) 需要强制转换的类，只有强制转换后才能访问到线程Thread对象，使用Synchronize来访问VCL控件

------------------------ Unit.pas ----------------------
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, IdSchedulerOfThreadPool, IdYarn,
  IdScheduler, IdBaseComponent, IdSchedulerOfThread, Spin;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    IdSchedulerOfThreadPool1: TIdSchedulerOfThreadPool;
    Button4: TButton;
    Button2: TButton;
    SpinEdit1: TSpinEdit;
    Button3: TButton;
    procedure Button4Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  aStr: string;

implementation

uses
  UnitUploadTask;

{$R *.dfm}

procedure TForm1.Button4Click(Sender: TObject); //线程池添加线程
var
  mytask: TUploadTask;
  idYarn: TIdYarn;
  obj: UploadParamObj;
begin
  obj := UploadParamObj.Create;
  obj.str := SpinEdit1.Text;

  idYarn := IdSchedulerOfThreadPool1.AcquireYarn;
  mytask := TUploadTask.Create(idYarn, obj);
  IdSchedulerOfThreadPool1.StartYarn(idYarn, mytask);
end;

procedure TForm1.Button3Click(Sender: TObject); //线程池结束线程
begin
IdSchedulerOfThreadPool1.TerminateAllYarns;
end;

procedure TForm1.Button2Click(Sender: TObject); //查看活动线程数
begin
  with IdSchedulerOfThreadPool1.ActiveYarns.LockList do try
    ShowMessage(IntToStr(count));
  finally
    IdSchedulerOfThreadPool1.ActiveYarns.UnlockList;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject); //初始化线程池
begin
  IdSchedulerOfThreadPool1.Init;
end;

end.

------------------------------------- UnitUploadTask.pas ---------------------------------
unit UnitUploadTask;

interface

uses
  Classes, SysUtils, IdTask, IdYarn;

type
  UploadParamObj = class(TObject)
  public
    str: string;
  end;

  TUploadTask = class(TIdTask)
  private
    thread: TThread;
    trytime: Integer;
    procedure output;
  protected
      function Run: Boolean; override;
      procedure BeforeRun; override;
      procedure AfterRun; override;
  public
      constructor Create(AYarn: TIdYarn; obj: UploadParamObj);
  end;

implementation

uses
  Unit1, IdSchedulerOfThread;

constructor TUploadTask.Create(AYarn: TIdYarn; obj: UploadParamObj);
begin
  FData := obj;
  trytime := 3;
  thread := TIdYarnOfThread(AYarn).Thread;
  inherited Create(AYarn);
end;

function TUploadTask.Run: Boolean;
begin
  thread.Synchronize(thread, output);

  Sleep(5000);
  if trytime > 0 then
  begin
    Dec(trytime);
    result := True;
  end
  else
    Result := False;
end;

procedure TUploadTask.BeforeRun;
begin
  Form1.Memo1.Lines.Add('BeforeRun' + UploadParamObj(FData).str);
end;

procedure TUploadTask.AfterRun;
begin
  Form1.Memo1.Lines.Add('AfterRun' + UploadParamObj(FData).str);
end;

procedure TUploadTask.output;
begin
  Form1.Memo1.Lines.Add('上传开始,str=' + UploadParamObj(FData).str + ', try=' + IntToStr(trytime) +',id=' + IntToStr(thread.ThreadID));
end;

end.

操作你会发现，线程池是用抛出异常来实现，因此你需要捕获异常来进行线程池满的处理。