我试图让我的应用程序只在计算机上运行一次,我的应用程序需要通信到web服务,所以让它运行不止一次是不好的,目前我正在使用Mutex：
MyMsg := RegisterWindowMessage('My_Unique_App_Message_Name');
Mutex := CreateMutex(nil,True,'My_Unique_Application_Mutex_Name');
if (Mutex = 0) OR (GetLastError = ERROR_ALREADY_EXISTS) then
exit;
目前这可以限制每个用户的1个应用程序实例,但我的应用程序正在Windows服务器环境中使用,一次有20个用户,所以我需要严格要求每个服务器只运行一次,我是什么试图做的是将Mutex声明为全局互斥锁,但是当我执行下一个代码时它没有这样做它根本不起作用.
MyMsg := RegisterWindowMessage('My_Unique_App_Message_Name');
Mutex := CreateMutex(nil,'Global\My_Unique_Application_Mutex_Name');
if (Mutex = 0) OR (GetLastError = ERROR_ALREADY_EXISTS) then
begin
exit
我做错了什么？有没有其他可靠的方法不让我的应用程序的第二个实例运行？
解决方法
默认情况下,lpMutexAttributes = nil创建的互斥锁只能由运行该进程的用户访问.所有用户都需要访问互斥锁.
空DACL安全描述符
通过使用具有空DACL的安全描述符来执行此操作.请在下面找到我用于单实例应用程序/服务的代码
//Creates a mutex to see if the program is already running.
function IsSingleInstance(MutexName : string; KeepMutex : boolean = true):boolean;
const MUTEX_GLOBAL = 'Global\'; //Prefix to explicitly create the object in the global or session namespace. I.e. both client app (local user) and service (system account)
var MutexHandel : THandle;
SecurityDesc: TSecurityDescriptor;
SecurityAttr: TSecurityAttributes;
ErrCode : integer;
begin
// By default (lpMutexAttributes =nil) created mutexes are accessible only by
// the user running the process. We need our mutexes to be accessible to all
// users,so that the mutex detection can work across user sessions.
// I.e. both the current user account and the System (Service) account.
// To do this we use a security descriptor with a null DACL.
InitializeSecurityDescriptor(@SecurityDesc,SECURITY_DESCRIPTOR_REVISION);
SetSecurityDescriptorDacl(@SecurityDesc,nil,False);
SecurityAttr.nLength:=SizeOf(SecurityAttr);
SecurityAttr.lpSecurityDescriptor:=@SecurityDesc;
SecurityAttr.bInheritHandle:=False;
// The mutex is created in the global name space which makes it possible to
// access across user sessions.
MutexHandel := CreateMutex(@SecurityAttr,PChar(MUTEX_GLOBAL + MutexName));
ErrCode := GetLastError;
// If the function fails,the return value is 0
// If the mutex is a named mutex and the object existed before this function
// call,the return value is a handle to the existing object,GetLastError
// returns ERROR_ALREADY_EXISTS.
if {(MutexHandel = 0) or }(ErrCode = ERROR_ALREADY_EXISTS) then
begin
result := false;
closeHandle(MutexHandel);
end
else
begin
// Mutex object has not yet been created,meaning that no prevIoUs
// instance has been created.
result := true;
if not KeepMutex then
CloseHandle(MutexHandel);
end;
// The Mutexhandle is not closed because we want it to exist during the
// lifetime of the application. The system closes the handle automatically
//when the process terminates.
end;