ASP.NET Core中IOC容器的實現原理

本章將和你們分享ASP.NET Core中IOC容器的實現原理。html

首先咱們須要瞭解什麼是IOC,爲何要使用IOC容器?ide

1、依賴

類A用到了類B,咱們就說類A依賴類B。函數

using System;

namespace MyIOCDI
{
    public class Test
    {
        public void Show()
        {
            MyDependency myDependency = new MyDependency(); //全是細節
            myDependency.Show();
            Console.WriteLine($"This is {this.GetType().FullName}");
        }
    }

    public class MyDependency
    {
        public void Show()
        {
            Console.WriteLine($"This is {this.GetType().FullName}");
        }
    }
}

上面的示例中,類Test就依賴了MyDependency類。測試

2、依賴倒置原則(Dependence Inversion Principle)

依賴倒置原則:高層模塊不該該依賴於低層模塊,兩者都應該依賴於抽象。應該依賴於抽象,而不是依賴細節。this

什麼是高層模塊?這裏的使用者Test類就稱爲高層模塊。什麼是低層模塊?被使用者MyDependency類就稱爲低層模塊。上面的示例中咱們的高層模塊就依賴於咱們的低層模塊。spa

那麼這樣子有什麼很差呢?線程

  一、面嚮對象語言開發,就是類與類之間進行交互,若是高層直接依賴低層的細節,細節是多變的,那麼低層的變化就致使上層的變化;3d

  二、若是層數多了,低層的修改會直接水波效應傳遞到最上層,一點細微的改動都會致使整個系統從下往上的修改。code

所以,上例按照依賴倒置原則修改以下:htm

using System;

namespace MyIOCDI
{
    public class Test
    {
        public void Show()
        {
            IDepenency myDependency = new MyDependency(); //左邊抽象右邊細節
            myDependency.Show();
            Console.WriteLine($"This is {this.GetType().FullName}");
        }
    }

    public class MyDependency : IDepenency
    {
        public void Show()
        {
            Console.WriteLine($"This is {this.GetType().FullName}");
        }
    }

    public interface IDepenency
    {
        void Show();
    }
}

3、IOC控制反轉

控制反轉是一種思想,所謂「控制反轉」就是反轉得到依賴對象的過程。

上面示例通過改造後雖然遵循了「依賴倒置原則」,可是違背了「開放封閉原則」,由於若是有一天想要修改變量myDependency爲YourDependency類的實例,則須要修改Test類。

所以,咱們須要反轉這種建立對象的過程:

using System;

namespace MyIOCDI
{
    public class Test
    {
        private readonly IDepenency _myDependency;
        public Test(IDepenency myDependency)
        {
            this._myDependency = myDependency;
        }

        public void Show()
        {
            _myDependency.Show();
            Console.WriteLine($"This is {this.GetType().FullName}");
        }
    }

    public class MyDependency : IDepenency
    {
        public void Show()
        {
            Console.WriteLine($"This is {this.GetType().FullName}");
        }
    }

    public interface IDepenency
    {
        void Show();
    }
}

上例中,將 _myDependency 的建立過程「反轉」給了調用者。

4、依賴注入(Dependency Injection)

依賴注入是一種在類及其依賴對象之間實現控制反轉(IOC)思想的技術。

所謂依賴注入,就是由IOC容器在運行期間,動態地將某種依賴關係注入到對象之中。

依賴注入就是能作到構造某個對象時,將依賴的對象自動初始化並注入 。

IOC是目標是效果,須要DI依賴注入的手段。

三種注入方式:構造函數注入--屬性注入--方法注入(按時間順序)。

構造函數注入用的最多,默認找參數最多的構造函數,能夠不用特性,能夠去掉對容器的依賴。

5、IOC容器的實現原理

IOC容器的實現原理:

  一、啓動時保存註冊信息。

  二、在構造某個對象時,根據註冊信息使用反射加特性,將依賴的對象自動初始化並注入。

  三、對對象進行生命週期管理或者進行AOP擴展等。

下面咱們重點來看下如何建立一個簡易的IOC容器(固然,實際使用的IOC容器要比這複雜的多)。

首先來看下項目的目錄結構:

此處IOC容器中用到的自定義特性以下所示:

using System;

namespace TianYaSharpCore.IOCDI.CustomAttribute
{
    /// <summary>
    /// 構造函數注入特性
    /// </summary>
    [AttributeUsage(AttributeTargets.Constructor)]
    public class ConstructorInjectionAttribute : Attribute
    {

    }
}
using System;

namespace TianYaSharpCore.IOCDI.CustomAttribute
{
    /// <summary>
    /// 方法注入特性
    /// </summary>
    [AttributeUsage(AttributeTargets.Method)]
    public class MethodInjectionAttribute : Attribute
    {

    }
}
using System;

namespace TianYaSharpCore.IOCDI.CustomAttribute
{
    /// <summary>
    /// 常量
    /// </summary>
    [AttributeUsage(AttributeTargets.Parameter)]
    public class ParameterConstantAttribute : Attribute
    {

    }
}
using System;

namespace TianYaSharpCore.IOCDI.CustomAttribute
{
    /// <summary>
    /// 簡稱(別名)
    /// </summary>
    [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property)]
    public class ParameterShortNameAttribute : Attribute
    {
        public string ShortName { get; private set; }
        public ParameterShortNameAttribute(string shortName)
        {
            this.ShortName = shortName;
        }
    }
}
using System;

namespace TianYaSharpCore.IOCDI.CustomAttribute
{
    /// <summary>
    /// 屬性注入特性
    /// </summary>
    [AttributeUsage(AttributeTargets.Property)]
    public class PropertyInjectionAttribute : Attribute
    {

    }
}

建立一個簡易的IOC容器,以下所示:

using System;

namespace TianYaSharpCore.IOCDI.CustomContainer
{
    public class IOCContainerRegistModel
    {
        public Type TargetType { get; set; }

        /// <summary>
        /// 生命週期
        /// </summary>
        public LifetimeType Lifetime { get; set; }

        /// <summary>
        /// 僅限單例
        /// </summary>
        public object SingletonInstance { get; set; }
    }

    /// <summary>
    /// 生命週期
    /// </summary>
    public enum LifetimeType
    {
        Transient, //瞬時
        Singleton,
        Scope, //做用域
        PerThread //線程單例
        //外部可釋放單例
    }
}
using System;

namespace TianYaSharpCore.IOCDI.CustomContainer
{
    /// <summary>
    /// IOC容器接口
    /// </summary>
    public interface ITianYaIOCContainer
    {
        void Register<TFrom, TTo>(string shortName = null, object[] paraList = null, LifetimeType lifetimeType = LifetimeType.Transient)
            where TTo : TFrom;
        TFrom Resolve<TFrom>(string shortName = null);
        ITianYaIOCContainer CreateChildContainer();
    }
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

using TianYaSharpCore.IOCDI.CustomAttribute;

namespace TianYaSharpCore.IOCDI.CustomContainer
{
    /// <summary>
    /// IOC容器
    /// </summary>
    public class TianYaIOCContainer : ITianYaIOCContainer
    {
        #region 字段或者屬性

        /// <summary>
        /// 保存註冊信息
        /// </summary>
        private Dictionary<string, IOCContainerRegistModel> _tianYaContainerDictionary = new Dictionary<string, IOCContainerRegistModel>();

        /// <summary>
        /// 保存常量的值
        /// </summary>
        private Dictionary<string, object[]> _tianYaContainerValueDictionary = new Dictionary<string, object[]>();

        /// <summary>
        /// 做用域單例的對象
        /// </summary>
        private Dictionary<string, object> _tianYaContainerScopeDictionary = new Dictionary<string, object>();

        #endregion 字段或者屬性

        #region 構造函數

        /// <summary>
        /// 無參構造行數
        /// </summary>
        public TianYaIOCContainer()
        {

        }

        /// <summary>
        /// 主要在建立子容器的時候使用
        /// </summary>
        private TianYaIOCContainer(Dictionary<string, IOCContainerRegistModel> tianYaContainerDictionary,
            Dictionary<string, object[]> tianYaContainerValueDictionary, Dictionary<string, object> tianYaContainerScopeDictionary)
        {
            this._tianYaContainerDictionary = tianYaContainerDictionary;
            this._tianYaContainerValueDictionary = tianYaContainerValueDictionary;
            this._tianYaContainerScopeDictionary = tianYaContainerScopeDictionary;
        }

        #endregion 構造函數

        /// <summary>
        /// 建立子容器
        /// </summary>
        public ITianYaIOCContainer CreateChildContainer()
        {
            return new TianYaIOCContainer(this._tianYaContainerDictionary, this._tianYaContainerValueDictionary,
                new Dictionary<string, object>()); //沒有註冊關係,最好能初始化進去
        }

        /// <summary>
        /// 獲取鍵
        /// </summary>
        private string GetKey(string fullName, string shortName) => $"{fullName}___{shortName}";

        /// <summary>
        /// 加個參數區分生命週期--並且註冊關係得保存生命週期
        /// </summary>
        /// <typeparam name="TFrom">要添加的服務的類型</typeparam>
        /// <typeparam name="TTo">要使用的實現的類型</typeparam>
        /// <param name="shortName">簡稱(別名)(主要用於解決單接口多實現)</param>
        /// <param name="paraList">常量參數</param>
        /// <param name="lifetimeType">生命週期</param>
        public void Register<TFrom, TTo>(string shortName = null, object[] paraList = null, LifetimeType lifetimeType = LifetimeType.Transient)
            where TTo : TFrom
        {
            this._tianYaContainerDictionary.Add(this.GetKey(typeof(TFrom).FullName, shortName), new IOCContainerRegistModel()
            {
                Lifetime = lifetimeType,
                TargetType = typeof(TTo)
            });

            if (paraList != null && paraList.Length > 0)
            {
                this._tianYaContainerValueDictionary.Add(this.GetKey(typeof(TFrom).FullName, shortName), paraList);
            }
        }

        /// <summary>
        /// 獲取對象
        /// </summary>
        public TFrom Resolve<TFrom>(string shortName = null)
        {
            return (TFrom)this.ResolveObject(typeof(TFrom), shortName);
        }

        /// <summary>
        /// 遞歸--能夠完成不限層級的對象建立
        /// </summary>
        private object ResolveObject(Type abstractType, string shortName = null)
        {
            string key = this.GetKey(abstractType.FullName, shortName);
            var model = this._tianYaContainerDictionary[key];

            #region 生命週期

            switch (model.Lifetime)
            {
                case LifetimeType.Transient:
                    Console.WriteLine("Transient Do Nothing Before");
                    break;
                case LifetimeType.Singleton:
                    if (model.SingletonInstance == null)
                    {
                        break;
                    }
                    else
                    {
                        return model.SingletonInstance;
                    }
                case LifetimeType.Scope:
                    if (this._tianYaContainerScopeDictionary.ContainsKey(key))
                    {
                        return this._tianYaContainerScopeDictionary[key];
                    }
                    else
                    {
                        break;
                    }
                default:
                    break;
            }

            #endregion 生命週期

            Type type = model.TargetType;

            #region 選擇合適的構造函數

            ConstructorInfo ctor = null;
            //標記特性
            ctor = type.GetConstructors().FirstOrDefault(c => c.IsDefined(typeof(ConstructorInjectionAttribute), true));
            if (ctor == null)
            {
                //參數個數最多
                ctor = type.GetConstructors().OrderByDescending(c => c.GetParameters().Length).First();
            }
            //ctor = type.GetConstructors()[0]; //直接第一個

            #endregion 選擇合適的構造函數

            #region 準備構造函數的參數

            List<object> paraList = new List<object>();
            object[] paraConstant = this._tianYaContainerValueDictionary.ContainsKey(key) ? this._tianYaContainerValueDictionary[key] : null; //常量找出來
            int iIndex = 0;
            foreach (var para in ctor.GetParameters())
            {
                if (para.IsDefined(typeof(ParameterConstantAttribute), true))
                {
                    paraList.Add(paraConstant[iIndex]);
                    iIndex++;
                }
                else
                {
                    Type paraType = para.ParameterType; //獲取參數的類型
                    string paraShortName = this.GetShortName(para);
                    object paraInstance = this.ResolveObject(paraType, paraShortName);
                    paraList.Add(paraInstance);
                }
            }

            #endregion 準備構造函數的參數

            object oInstance = null;
            oInstance = Activator.CreateInstance(type, paraList.ToArray()); //建立對象,完成構造函數的注入

            #region 屬性注入

            foreach (var prop in type.GetProperties().Where(p => p.IsDefined(typeof(PropertyInjectionAttribute), true)))
            {
                Type propType = prop.PropertyType;
                string paraShortName = this.GetShortName(prop);
                object propInstance = this.ResolveObject(propType, paraShortName);
                prop.SetValue(oInstance, propInstance);
            }

            #endregion 屬性注入

            #region 方法注入 

            foreach (var method in type.GetMethods().Where(m => m.IsDefined(typeof(MethodInjectionAttribute), true)))
            {
                List<object> paraInjectionList = new List<object>();
                foreach (var para in method.GetParameters())
                {
                    Type paraType = para.ParameterType;//獲取參數的類型 IUserDAL
                    string paraShortName = this.GetShortName(para);
                    object paraInstance = this.ResolveObject(paraType, paraShortName);
                    paraInjectionList.Add(paraInstance);
                }
                method.Invoke(oInstance, paraInjectionList.ToArray());
            }

            #endregion 方法注入

            #region 生命週期

            switch (model.Lifetime)
            {
                case LifetimeType.Transient:
                    Console.WriteLine("Transient Do Nothing After");
                    break;
                case LifetimeType.Singleton:
                    model.SingletonInstance = oInstance;
                    break;
                case LifetimeType.Scope:
                    this._tianYaContainerScopeDictionary[key] = oInstance;
                    break;
                default:
                    break;
            }

            #endregion 生命週期

            //return oInstance.AOP(abstractType); //AOP擴展
            return oInstance;
        }

        /// <summary>
        /// 獲取簡稱(別名)
        /// </summary>
        private string GetShortName(ICustomAttributeProvider provider)
        {
            if (provider.IsDefined(typeof(ParameterShortNameAttribute), true))
            {
                var attribute = (ParameterShortNameAttribute)(provider.GetCustomAttributes(typeof(ParameterShortNameAttribute), true)[0]);
                return attribute.ShortName;
            }
            else
            {
                return null;
            }
        }
    }
}

至此,咱們就建立完了一個簡易的IOC容器。

下面咱們來添加一些用於測試的接口,以下所示:

using System;

namespace MyIOCDI.IService
{
    public interface ITestServiceA
    {
        void Show();
    }
}
using System;

namespace MyIOCDI.IService
{
    public interface ITestServiceB
    {
        void Show();
    }
}
using System;

namespace MyIOCDI.IService
{
    public interface ITestServiceC
    {
        void Show();
    }
}
using System;

namespace MyIOCDI.IService
{
    public interface ITestServiceD
    {
        void Show();
    }
}

接口對應的實現,以下所示:

using System;

using MyIOCDI.IService;

namespace MyIOCDI.Service
{
    public class TestServiceA : ITestServiceA
    {
        public TestServiceA()
        {
            Console.WriteLine($"{this.GetType().Name}被構造。。。");
        }

        public void Show()
        {
            Console.WriteLine($"This is {this.GetType().Name} Show");
        }
    }
}
using System;

using MyIOCDI.IService;

namespace MyIOCDI.Service
{
    public class TestServiceB : ITestServiceB
    {
        public TestServiceB()
        {
            Console.WriteLine($"{this.GetType().Name}被構造。。。");
        }

        public void Show()
        {
            Console.WriteLine($"This is {this.GetType().Name} Show");
        }
    }
}
using System;

using MyIOCDI.IService;

namespace MyIOCDI.Service
{
    public class TestServiceC : ITestServiceC
    {
        public TestServiceC()
        {
            Console.WriteLine($"{this.GetType().Name}被構造。。。");
        }

        public void Show()
        {
            Console.WriteLine($"This is {this.GetType().Name} Show");
        }
    }
}
using System;

using MyIOCDI.IService;
using TianYaSharpCore.IOCDI.CustomAttribute;

namespace MyIOCDI.Service
{
    public class TestServiceD : ITestServiceD
    {
        /// <summary>
        /// 屬性注入
        /// </summary>
        [PropertyInjection]
        public ITestServiceA TestServiceA { get; set; }

        /// <summary>
        /// 帶有別名的屬性注入
        /// </summary>
        [ParameterShortName("ServiceB")]
        [PropertyInjection]
        public ITestServiceB TestServiceB { get; set; }

        public TestServiceD()
        {
            Console.WriteLine($"{this.GetType().Name}被構造。。。");
        }

        #region 構造函數注入

        private readonly ITestServiceA _testServiceA;
        private readonly ITestServiceB _testServiceB;
        [ConstructorInjection] //優先選擇帶有構造函數注入特性的
        public TestServiceD(ITestServiceA testServiceA, [ParameterConstant] string sValue, ITestServiceB testServiceB, [ParameterConstant] int iValue)
        {
            Console.WriteLine($"{this.GetType().Name}--{sValue}--{iValue}被構造。。。");
            _testServiceA = testServiceA;
            _testServiceB = testServiceB;
        }

        #endregion 構造函數注入

        #region 方法注入

        private ITestServiceC _testServiceC;
        [MethodInjection]
        public void Init(ITestServiceC testServiceC)
        {
            _testServiceC = testServiceC;
        }

        #endregion 方法注入

        public void Show()
        {
            Console.WriteLine($"This is {this.GetType().Name} Show");
        }
    }
}

最後來看下IOC容器的使用及其運行結果:

using System;

using TianYaSharpCore.IOCDI.CustomContainer;
using MyIOCDI.IService;
using MyIOCDI.Service;

namespace MyIOCDI
{
    class Program
    {
        static void Main(string[] args)
        {
            ITianYaIOCContainer container = new TianYaIOCContainer();
            {
                //註冊
                container.Register<ITestServiceA, TestServiceA>(); //將ITestServiceA註冊到TestServiceA
                container.Register<ITestServiceB, TestServiceB>();
                container.Register<ITestServiceB, TestServiceB>(shortName: "ServiceB");
                container.Register<ITestServiceC, TestServiceC>();
                container.Register<ITestServiceD, TestServiceD>(paraList: new object[] { "浪子天涯", 666 }, lifetimeType: LifetimeType.Singleton);

                ITestServiceD d1 = container.Resolve<ITestServiceD>(); //建立對象交給IOC容器
                ITestServiceD d2 = container.Resolve<ITestServiceD>();
                d1.Show();
                Console.WriteLine($"object.ReferenceEquals(d1, d2) = {object.ReferenceEquals(d1, d2)}");
            }

            Console.ReadKey();
        }
    }
}

運行結果以下:

生命週期爲做用域的,其實就是子容器單例,以下所示:

using System;

using TianYaSharpCore.IOCDI.CustomContainer;
using MyIOCDI.IService;
using MyIOCDI.Service;

namespace MyIOCDI
{
    class Program
    {
        static void Main(string[] args)
        {
            ITianYaIOCContainer container = new TianYaIOCContainer();
            //{
            //    //註冊
            //    container.Register<ITestServiceA, TestServiceA>(); //將ITestServiceA註冊到TestServiceA
            //    container.Register<ITestServiceB, TestServiceB>();
            //    container.Register<ITestServiceB, TestServiceB>(shortName: "ServiceB");
            //    container.Register<ITestServiceC, TestServiceC>();
            //    container.Register<ITestServiceD, TestServiceD>(paraList: new object[] { "浪子天涯", 666 }, lifetimeType: LifetimeType.Singleton);

            //    ITestServiceD d1 = container.Resolve<ITestServiceD>(); //建立對象交給IOC容器
            //    ITestServiceD d2 = container.Resolve<ITestServiceD>();
            //    d1.Show();
            //    Console.WriteLine($"object.ReferenceEquals(d1, d2) = {object.ReferenceEquals(d1, d2)}");
            //}

            {
                //生命週期:做用域
                //就是Http請求時,一個請求處理過程當中,建立都是同一個實例;不一樣的請求處理過程當中,就是不一樣的實例;
                //得區分請求,Http請求---Asp.NetCore內置Kestrel,初始化一個容器實例;而後每次來一個Http請求,就clone一個,
                //或者叫建立子容器(包含註冊關係),而後一個請求就一個子容器實例,那麼就能夠作到請求單例了(其實就是子容器單例)
                //主要能夠去作DbContext  Repository
                container.Register<ITestServiceA, TestServiceA>(lifetimeType: LifetimeType.Scope);
                ITestServiceA a1 = container.Resolve<ITestServiceA>();
                ITestServiceA a2 = container.Resolve<ITestServiceA>();

                Console.WriteLine(object.ReferenceEquals(a1, a2)); //T

                ITianYaIOCContainer container1 = container.CreateChildContainer();
                ITestServiceA a11 = container1.Resolve<ITestServiceA>();
                ITestServiceA a12 = container1.Resolve<ITestServiceA>();

                ITianYaIOCContainer container2 = container.CreateChildContainer();
                ITestServiceA a21 = container2.Resolve<ITestServiceA>();
                ITestServiceA a22 = container2.Resolve<ITestServiceA>();

                Console.WriteLine(object.ReferenceEquals(a11, a12)); //T
                Console.WriteLine(object.ReferenceEquals(a21, a22)); //T

                Console.WriteLine(object.ReferenceEquals(a11, a21)); //F
                Console.WriteLine(object.ReferenceEquals(a11, a22)); //F
                Console.WriteLine(object.ReferenceEquals(a12, a21)); //F
                Console.WriteLine(object.ReferenceEquals(a12, a22)); //F
            }

            Console.ReadKey();
        }
    }
}

運行結果以下:

至此本文就所有介紹完了,若是以爲對您有所啓發請記得點個贊哦!!!

 

Demo源碼:

連接:https://pan.baidu.com/s/15xpmWbEDbkm7evpr4iIZNg 
提取碼:ckes

此文由博主精心撰寫轉載請保留此原文連接:https://www.cnblogs.com/xyh9039/p/13663808.html

相關文章
相關標籤/搜索