就是我有个mail收发程序，要求在windows，linux，unix上都能作为系统服务使用。就是说在用户登陆之前就在运行了，怎么做啊

Question

要实现这个,就目前的 Java 来说,基本上是"很难".

Answer 1

在windowns上可以通过设置run键值来实现

Answer 2

只能开发成系统服务，我这而有段代码：
using namespace std;
 
#ifdef  _DEBUG  
#define  new  DEBUG_NEW  
#undef  THIS_FILE  
static  char  THIS_FILE[]  =  __FILE__;  
#endif  
 
/////////////////////////////////////////////////////////////////////////////  
//  The  one  and  only  application  object  
 
CWinApp  theApp;  
 
using  namespace  std;  
SERVICE_STATUS_HANDLE  ssh;  
SC_HANDLE  scm,svc;  
SERVICE_STATUS  ss;  
CArray<PROCESSENTRY32,PROCESSENTRY32  &>  m_PEArray;  
void  WINAPI  ServiceMain(DWORD  dwArgc,  LPTSTR  *lpszArgv);  
void  WINAPI  Handler(DWORD  Opcode);  
void  InstallService();  
UINT  jiankong(LPVOID  lpvoid);
int  _tmain(int  argc,  TCHAR*  argv[],  TCHAR*  envp[])  
{  
           int  nRetCode  =  0;  
 
           //  initialize  MFC  and  print  and  error  on  failure  
           if  (!AfxWinInit(::GetModuleHandle(NULL),  NULL,  ::GetCommandLine(),  0))  
           {  
                       //  TODO:  change  error  code  to  suit  your  needs  
                       cerr  <<  _T("Fatal  Error:  MFC  initialization  failed")  <<  endl;  
                       nRetCode  =  1;  
           }  
           else  
           {  
                       //  TODO:  code  your  application's  behavior  here.  
                       SERVICE_TABLE_ENTRY  ste[2];  
                       //线程入口表  
                       ste[0].lpServiceName="load";  //线程名字  
                       ste[0].lpServiceProc=ServiceMain;  //线程入口地址  
                       //可以有多个线程，最后一个必须为NULL  
                       ste[1].lpServiceName=NULL;  
                       ste[1].lpServiceProc=NULL;  
                       StartServiceCtrlDispatcher(ste);  
                       InstallService();  
           }  
 
           return  nRetCode;  
}  
 
//安装并启动服务  
void  InstallService()  
{  
           LPTSTR  lpSysPath=new  char[MAX_PATH];  
           ::GetSystemDirectory(lpSysPath,MAX_PATH);  
           LPCTSTR  lpsysfilename;  
           lpsysfilename=(LPCTSTR)lstrcat(lpSysPath,"\\LoadUpdateService.exe");  
           scm=OpenSCManager(NULL,NULL,SC_MANAGER_ALL_ACCESS);  
           if(scm!=NULL)  
                       svc=CreateService(scm,"load","load",SERVICE_ALL_ACCESS,  
                       SERVICE_WIN32_OWN_PROCESS  |SERVICE_INTERACTIVE_PROCESS,SERVICE_AUTO_START,SERVICE_ERROR_IGNORE,lpsysfilename,NULL,NULL,NULL,NULL,NULL);  
           if(svc!=NULL)  
                       svc=OpenService(scm,"load",SERVICE_START);  
           if  (svc!=NULL)  
           {  
                       StartService(svc,0,NULL);  
                       CloseServiceHandle(svc);  
           }  
           CloseServiceHandle(scm);  
}  
//服务的真正入口点函数  
void  WINAPI  ServiceMain(DWORD  dwArgc,  LPTSTR  *lpszArgv)  
{  
           ss.dwServiceType  =  SERVICE_WIN32;  
           ss.dwCurrentState  =  SERVICE_START_PENDING;  
           ss.dwControlsAccepted  =  SERVICE_ACCEPT_STOP  |  SERVICE_ACCEPT_PAUSE_CONTINUE;  
           ss.dwServiceSpecificExitCode  =  0;  
           ss.dwWin32ExitCode  =  0;  
           ss.dwCheckPoint  =  0;  
           ss.dwWaitHint  =  0;  
           ssh=RegisterServiceCtrlHandler("load",Handler);  
           ss.dwCurrentState  =  SERVICE_RUNNING;  
           ss.dwCheckPoint  =  0;  
           ss.dwWaitHint  =  0;  
           SetServiceStatus(ssh,&ss);  
           AfxBeginThread(jiankong,NULL,NULL);  //开始一个工作线程实现程序功能  
           ss.dwCurrentState  =  SERVICE_RUNNING;  
           ss.dwCheckPoint  =  0;  
           ss.dwWaitHint  =  0;  
           SetServiceStatus(ssh,&ss);  
}  
//处理服务要求  
void  WINAPI  Handler(DWORD  Opcode)  
{  
           switch(Opcode)  
           {  
           case  SERVICE_CONTROL_STOP:  
                       ss.dwCurrentState  =SERVICE_STOPPED;  
                       SetServiceStatus  (ssh,&ss);  
                       break;  
           case  SERVICE_CONTROL_CONTINUE:  
                       ss.dwCurrentState  =  SERVICE_RUNNING;  
                       SetServiceStatus  (ssh,&ss);  
                       break;  
           case  SERVICE_CONTROL_PAUSE:  
                       ss.dwCurrentState  =  SERVICE_PAUSED;  
                       SetServiceStatus  (ssh,&ss);  
                       break;  
           case  SERVICE_CONTROL_INTERROGATE:  
                       break;  
           }  
           SetServiceStatus  (ssh,&ss);  
}  
UINT  jiankong(LPVOID  lParam)  
{
}