singleton

问题 well most of us familiar with this pattern: public class MySingeltone { public String mSomeReferenceTypeData; public int mSomeValueTypeData; private static MySingeltone mInstance; private MySingeltone() { } public static MySingeltone getInstance() { if (mInstance == null) { mInstance = new MySingeltone(); } return mInstance; } } my problem is that I've found recently that the mInstance don't equal null after activity using him been destroyed, or when the whole application suppose to be clause

问题 I am looking for a way to have a "Singleton" module over multiple worker role instances. I would like to have a parallel execution model with Queues and multiple worker roles in Azure. The idea is that would like to have a "master" instance, that is let's say checking for new data, and is scheduling it by adding it to a queue, processing all messages from a special queue, that is not processed by nobody else, and has mounted blob storage as a virtual drive, with read/write access. I will

问题 I'm writing a class which serves as base class for a series of singleton objects. In each singleton objects, there will be vals representing certain properties, and I want to write a method which, for each singleton object, only accepts objects created by it. So I have the following: class Obj[M <: Maker] class Maker { implicit val me: this.type = this def make[M <: Maker](implicit maker: M) = new Obj[M] def accept(obj: Obj[this.type]) = {...} } So far, so good. Then I want to declare one of

问题 This might sound complex but i will ask anyway: I am running a service A which uses class X . I want to start another service B which uses classes A besides new classes. Service A is already running. I do a hot deployment of Service B . Here is the real question - Will Service B use the same instance of class X or a separate instance. How can singleton class help me here? 回答1: Each Service will run in it's own operating System (OS) Process space, and each process space has it's own class

问题 I implemented a class called WebSocketClient which provides the functionality to open and connect to a websocket, send data through the websocket, etc... Now I want to use this class in my Activities. In order to be informed of incomming messages from the websocket i created a WebsocketListener which can be registered in the WebSocketClient so the activity which would like to communicate through the Websocket would implement this interface and register itself. The problem is, how can I use

问题 I'm trying to implement the singleton pattern in a database helper class, but, I can't seem to understand the purpose of a factory constructor and if there's an alternative method to using it. class DbHelper { final String tblName =''; final String clmnName =''; final String clmnPass=''; DbHelper._constr(); static final DbHelper _db = new DbHelper._constr(); factory DbHelper(){ return _db;} Database _mydb; Future<Database> get mydb async{ initDb() { if(_mydb != null) { return _mydb; } _mydb =

问题 I hate to beat a dead horse, that said, I've gone over so many conflicting articles over the past few days in regards to the use of the singleton pattern. This question isn't be about which is the better choice in general, rather what makes sense for my use case. The pet project I'm working on is a game. Some of the code that I'm currently working on, I'm leaning towards using a singleton pattern. The use cases are as follows: a globally accessible logger. an OpenGL rendering manager. file

问题 I was reading around a lot about singleton. I am thinking about the dead reference problem between singletons. In every primer on net , this problem is encountered when one singleton calls other singleton in its destructor, and that singleton is already destroyed, say Log singleton can be called from destructor of many other singletons. I can't imagine when in other case ( except referencing other singletons in dtr ), the dead reference would be a problem. Can you give me a real world example

问题 I have a .Net Core project that registers a number of Singletons as follows: public void ConfigureServices(IServiceCollection services) { services.AddMemoryCache(); services.AddLogging(); services.AddSingleton<IConfiguration>(Configuration); services.AddSingleton<IDbFactory, DefaultDbFactory>(); services.AddSingleton<IUserRepository, UserRepository>(); services.AddSingleton<IEmailService, EmailService>(); services.AddSingleton<IHostedService, BackgroundService>(); services.AddSingleton

问题 I have situation where I share singleton between my code which runs the embedded-server and my web-application. I have war with classes and deployment tool. When I printf instances I see: abc.Abc@173a10f abc.Abc@105738 So this is not really singleton. How this works? My server Jetty start code: public static void main(String[] args) throws Exception { System.out.println(MySingleton.getInstance()); // start Jetty here and deploy war with WebAppContext() } My ServletContextListener side code: