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本篇內(nèi)容介紹了“ASP.NET Core服務(wù)生命周期是什么”的有關(guān)知識,在實際案例的操作過程中,不少人都會遇到這樣的困境,接下來就讓小編帶領(lǐng)大家學(xué)習(xí)一下如何處理這些情況吧!希望大家仔細閱讀,能夠?qū)W有所成!
在ConfigureServices方法中的容器注冊每個應(yīng)用程序的服務(wù),Asp.Core都可以為每個應(yīng)用程序提供三種服務(wù)生命周期:
Transient(暫時):每次請求都會創(chuàng)建一個新的實例。這種生命周期最適合輕量級,無狀態(tài)服務(wù)。
Scoped(作用域):在同一個作用域內(nèi)只初始化一個實例 ,可以理解為每一個請求只創(chuàng)建一個實例,同一個請求會在一個作用域內(nèi)。
Singleton(單例):整個應(yīng)用程序生命周期以內(nèi)只創(chuàng)建一個實例,后續(xù)每個請求都使用相同的實例。如果應(yīng)用程序需要單例行為,建議讓服務(wù)容器管理服務(wù)的生命周期,而不是在自己的類中實現(xiàn)單例模式。
為了演示生命周期和注冊選項之間的差異,請考慮以下接口,將任務(wù)表示為具有唯一標識符 OperationId 的操作。根據(jù)以下接口配置操作服務(wù)的生命周期的方式,容器在類請求時提供相同或不同的服務(wù)實例:
public interface IOperation { Guid OperationId { get; } } public interface IOperationTransient : IOperation { } public interface IOperationScoped : IOperation { } public interface IOperationSingleton : IOperation { } public interface IOperationSingletonInstance : IOperation { }
上面四種服務(wù)接口在 Operation 類中實現(xiàn)。調(diào)用Operation類時將自動生成一個GUID,下面是Operation類的實現(xiàn):
public class Operation : IOperationTransient, IOperationScoped, IOperationSingleton, IOperationSingletonInstance { public Operation() : this(Guid.NewGuid()) { } public Operation(Guid id) { OperationId = id; } public Guid OperationId { get; private set; } }
再注冊一個OperationService服務(wù)實例,當(dāng)通過依賴關(guān)系注入請求 OperationService 實例時,它將接收每個服務(wù)的新實例或基于從屬服務(wù)(Operation)的生命周期的現(xiàn)有實例。OperationService 服務(wù)作用就是第二次調(diào)用 Operation類,查看Operation類實例的作用域變化。
public class OperationService { public OperationService( IOperationTransient transientOperation, IOperationScoped scopedOperation, IOperationSingleton singletonOperation, IOperationSingletonInstance instanceOperation) { _transientOperation = transientOperation; _scopedOperation = scopedOperation; _singletonOperation = singletonOperation; _singletonInstanceOperation = instanceOperation; } public IOperationTransient _transientOperation { get; } public IOperationScoped _scopedOperation { get; } public IOperationSingleton _singletonOperation { get; } public IOperationSingletonInstance _singletonInstanceOperation { get; } }
然后在Startup.ConfigureServices()服務(wù)容器中注冊各個生命周期的實例:
public void ConfigureServices(IServiceCollection services) { services.AddTransient<IOperationTransient, Operation>(); services.AddScoped<IOperationScoped, Operation>(); services.AddSingleton<IOperationSingleton, Operation>(); services.AddSingleton<IOperationSingletonInstance>(new Operation(Guid.Empty)); // OperationService depends on each of the other Operation types. services.AddTransient<OperationService, OperationService>(); }
再在IndexModel模塊里面調(diào)用OnGet方法輸出,觀察IOperation與OperationService類屬性O(shè)perationId 值的變化:
public class IndexModel : PageModel { public OperationService _operationService { get; } public IOperationTransient _transientOperation { get; } public IOperationScoped _scopedOperation { get; } public IOperationSingleton _singletonOperation { get; } public IOperationSingletonInstance _singletonInstanceOperation { get; } public IndexModel( OperationService operationService, IOperationTransient transientOperation, IOperationScoped scopedOperation, IOperationSingleton singletonOperation, IOperationSingletonInstance singletonInstanceOperation) { _operationService = operationService; _transientOperation = transientOperation; _scopedOperation = scopedOperation; _singletonOperation = singletonOperation; _singletonInstanceOperation = singletonInstanceOperation; } public void OnGet() { Console.WriteLine("IOperation操作:"); Console.WriteLine("暫時:" + _transientOperation.OperationId.ToString()); Console.WriteLine("作用域:" + _scopedOperation.OperationId.ToString()); Console.WriteLine("單例:" + _singletonOperation.OperationId.ToString()); Console.WriteLine("實例:" + _singletonInstanceOperation.OperationId.ToString()); Console.WriteLine("OperationService操作:"); Console.WriteLine("暫時:" + _operationService._transientOperation.OperationId.ToString()); Console.WriteLine("作用域:" + _operationService._scopedOperation.OperationId.ToString()); Console.WriteLine("單例:" + _operationService._singletonOperation.OperationId.ToString()); Console.WriteLine("實例:" + _operationService._singletonInstanceOperation.OperationId.ToString()); } }
執(zhí)行IndexModel 類輸出結(jié)果:
由圖總結(jié)如下:
2.1 Transient(暫時):每次調(diào)用服務(wù)的時候都會創(chuàng)建一個新的實例。即在IndexModel類的局部方法或?qū)傩灾校ㄟ@里是OnGet方法)實例化一個依賴對象Operation類,偽代碼是:
public class IndexModel: PageModel { public void OnGet() { //調(diào)用IndexModel類時,實例化了兩次Operation類 //第一次 OperationService operationService=new OperationService(); //第二次 IOperationTransient TransientOperation=new Operation(); } }
2.2 Scoped(作用域):一次請求(Action)內(nèi)對象實例是相同的,但每次請求會產(chǎn)生一個新實例。相當(dāng)于在IndexModel類的全局中實例化一次依賴對象Operation類,偽代碼是:
OperationService operationService = null; public IndexModel() { operationService = new OperationService(); operationService._scopedOperation = new Operation(); } public void OnGet() { operationService._scopedOperation.OperationId; IOperationScoped operationScoped = operationService._scopedOperation; operationScoped.OperationId }
2.3 Singleton(單例):首次請求初始化同一個實例,后續(xù)每次請求都使用同一個實例。相當(dāng)于在整個應(yīng)用Application中只實例化一次實例,常見的單例模式。
生命周期流程圖如下:
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