synchronization

问题 Background: My WCF application has to call a service that does not have any concurrency checking in it. It is a service created by a third party and getting them to add concurrency checking may not be possible. I can ensure that the only way to call the third party service is via my WCF application. So I am considering putting concurrency checking in my code. To do this, I will use an identifier that uniquely describes the data being modified. The idea is that if one call to the service is

问题 I'm creating a 20-minute countdown timer application. I'm using JavaFX SceneBuilder to do this. The timer is composed of two labels (one for minutes, one for seconds--each composed of a CountdownTimer class object), and a progress bar (the timer looks like this). Each of these components are separate and running on separate threads concurrently to prevent the UI from freezing up. And it works. The problem: The three threads ( minutesThread , secondsThread , progressBarUpdaterThread ) I need

问题 I'm creating a 20-minute countdown timer application. I'm using JavaFX SceneBuilder to do this. The timer is composed of two labels (one for minutes, one for seconds--each composed of a CountdownTimer class object), and a progress bar (the timer looks like this). Each of these components are separate and running on separate threads concurrently to prevent the UI from freezing up. And it works. The problem: The three threads ( minutesThread , secondsThread , progressBarUpdaterThread ) I need

问题 I am implementing multithreaded C++ program for Linux platform where I need a functionality similar to WaitForMultipleObjects(). While searching for the solution I observed that there are articles that describe how to achieve WaitForMultipleObjects() functionality in Linux with examples but those examples does not satisfy the scenario that I have to support. The scenario in my case is pretty simple. I have a daemon process in which the main thread exposes a method/callback to the outside

问题 I want to get output from two processes and merge them into one file, like: proc1 >> output & proc2 >> output & The problem is that output may be mixed up in the final file. For example if first process writes: hellow and the second process writes: bye the result may be something like: hebylloe but I expect them to be in seperate lines like (order is not important): bye hello So I used flock to synchronize writing to the file with the following script: exec 200>>output while read line; flock

问题 I have two functions: First, whenever user asks for a value based on key, i search the database and store the result in cache for faster future references. @Cacheable notation helped me in achieving this. Second, whenever user wants to update the value, instead of directly doing the db update operation, I want to update the cache and use a scheduled task to later update the db. I used @CachePut for this. @Cacheable(key="#id") public String getDoc(String id){ // fetch value from database

问题 This question already has answers here : Synchronizing on String objects in Java (19 answers) Closed 2 years ago . Let's say I have a method that creates a new user for a web application. The method itself calls a static helper class that creates a SQL statement that performs the actual insertion into my DB. public void createUserInDb(String userName){ SQLHelper.insertUser(userName); } I want to synchronize this method such that it cannot be called concurrently by different threads if the

问题 I want to send a $http.get if the page gets closed. Then I stumbold upon a problem where promises can't get resolved because if this one last method returns, the page gets destroyed. The following does not work because onbeforeunload can't resolve promises / does not wait for them: window.onbeforeunload = function( $http.get('http://someth.ing/update-state?page=unloaded').then(function(){ // never called... never sent... } } I know, you can use default sync HTTP Methods but the question is

问题 I want to develop application same as UBER in which I need to show available taxis in the selected region and update as the taxis are hired, available, unavailable. Kind of auto refresh. Calling the web service in the background after regular time interval is not a good option. Can any one suggest me better and fast way to achieve this. Thanks 回答1: Push Use sockets when the app is running. This will give you immediate updates. Use Push notifications when the app is not running (use

问题 I want to develop application same as UBER in which I need to show available taxis in the selected region and update as the taxis are hired, available, unavailable. Kind of auto refresh. Calling the web service in the background after regular time interval is not a good option. Can any one suggest me better and fast way to achieve this. Thanks 回答1: Push Use sockets when the app is running. This will give you immediate updates. Use Push notifications when the app is not running (use