synchronization

问题 I am creating a piece of code that gets a webpage from a legacy system we have. In order to avoid excessive querying, I am caching the obtained URL. I am using Monitor.Enter , Monitor.Exit and double checking to avoid that request is issued twice, but when releasing the lock with Monitor.Exit , I am getting this exception: System.Threading.SynchronizationLockException was caught HResult=-2146233064 Message=Object synchronization method was called from an unsynchronized block of code. Source

问题 I need to create an method invoker that any thread (Thread B for example sake) can call, which will execute on the main executing thread (Thead A) at a specific given point in its execution. Example usage would be as follows: static Invoker Invoker = new Invoker(); static void ThreadA() { new Thread(ThreadB).Start(); Thread.Sleep(...); // Hypothetic Alpha Invoker.Invoke(delegate { Console.WriteLine("Action"); }, true); Console.WriteLine("Done"); Console.ReadLine(); } static void ThreadB() {

问题 I´m having some problems with react. I´m using map function at render and the function componentDidMount is being called before it finish. Here snippet of my code componentDidMount: function() { console.info("didMount"); }, render: function() { return React.createElement("div", null, this.state.fields.map(function(field) { console.info("field" + field); return React.createElement("span", null, field); }.bind(this))); } It being printed "didMount" before "field...". How can i solve this? It

问题 I have seen many Questions on foreign key constraints problem and what I got is that By default, the following constraints are not copied to the client: FOREIGN KEY constraints, UNIQUE constraints, and DEFAULT constraints in this document: http://msdn.microsoft.com/en-us/library/bb726037.aspx So, it appears I have to "manually" create the relationships, once the schema is created on the client. Once relationship has been created on client side, what if I make any changes in tables on server

问题 I want to wait() the put() method called from the second thread which has been connected to the Server (Monitor). But when i do this, the whole GUI frames (Swing) including their elements get frozen aftr the second put() call. How to fix this? I want the second thread keep waiting till the first thread performs a get() which frees a slot. Thanks in advance. Here's my skeleton code: Server: Buffer<String> buf = new Buffer<String>(1); while(true){ //for each socket connected new ServerHandler(.

问题 If I synchronize on an array, does this mean that I'm synchronizing on all the elements in it or am I synchronizing on the array object? If the latter is true, then how can I synchronize on all the elements in an array at once so that I can make sure non will be accessed while executing a certain block? E.g. Lets say we have an array of bank accounts and we want to make sure no thread can access any account when a certain block of code is being executed. 回答1: It synchronizes on the monitor

问题 I have a Windows service as shown below: Protected Overrides Sub OnStart(ByVal args() As String) Dim timer As System.Timers.Timer = New System.Timers.Timer() timer.Interval = 1000 '1 sec AddHandler timer.Elapsed, AddressOf Me.OnTimer timer.Start() End Sub Private Sub OnTimer(sender As Object, e As Timers.ElapsedEventArgs) Dim Time As String = DateTime.Now.ToString("hh:mm:ss tt") If Time = "01:58:15 PM" Or Time = "02:42:15 PM" Or Time = "02:43:15 PM" _ Or Time = "03:44:15 PM" Or Time = "06:00

问题 I'm working on a service that runs in a java app server farm that needs to do some periodic jobs (say, once every 2 minutes). The service must interface to external entities, and it is necessary to synchronize the different instances so that only one of them works on the job at a given time. Since the service uses a DB during this job, I thought of implementing the synchronization based on a simple DB table: id, owner, stamp where id is the lock's id, owner is the current owner and stamp is

问题 My problem is illustrated below. Notification on std::condition_variable can be missed by Thread II; Thread III can acquire lock before it and change the condition. /* Thread I Thread II Thread III _____________________________________________________________ | lock M | wait for notify | wait for M | | | cond = stateA | | | | | notify | unblock | | | | unlock M | wait for M | lock M | | | | | cond = stateB | | | | lock M | unblock M | | | | check if cond == stateA | | | | | ... | | \ / t * */

问题 I have often come across this snippet : { SwingUtilities.invokeLater(new Runnable() { public void run() { new tester(); // class name } }); } I know why are we using this,but cannot understand how it is going.I mean i dont understand this snippet. (We are initializing object under run method,,,why?? ) Please explain this 回答1: With that bit of code you're creating a Inner Class that implements Runnable , that instance will be enqueued in the AWT processing task dispatcher for later processing