Provider模式应用demo

参考ObjectPool对象池设计原理还原一个简易的Provider模式。

using System;

using System.Dynamic;

using System.Reflection.Metadata.Ecma335;

using System.Threading;

using System.Xml;

namespace ProviderPattern

{

    /// <summary>

    /// 目标

    /// </summary>

    /// <typeparam name="T"></typeparam>

    public class TargetClass<T> where T:class

    {

        private ObjectWrapper[] _items;

        private ITargetClassPolicy<T> _policy;

        public TargetClass(ITargetClassPolicy<T> policy)

        {

            _policy = policy;

            _items = new ObjectWrapper[3];

        }

        public T Get()

        {

            var items = _items;

            for (var i = 0; i < items.Length; i++)

            {

                var item = items[i].Element;

                if (item != null && Interlocked.CompareExchange(ref items[i].Element, null,item) != null)

                {

                    return item;

                }

            }

            return Create();

        }

        public void Return(T obj)

        {

            if (!_policy.Return(obj))

            {

                return;

            }

            var items = _items;

            for (var i = 0; i < items.Length && Interlocked.CompareExchange(ref items[i].Element, obj, null) != null; ++i)

            {

            }

        }

        private T Create() => _policy.Create();

        private struct ObjectWrapper

        {

            public T Element;

        }

    }

    /// <summary>

    /// Provider 提供者

    /// </summary>

    public class TargetClassProvider

    {

        public TargetClass<T> Create<T>(ITargetClassPolicy<T> policy) where T : class, new()

        {

            return new TargetClass<T>(policy);

        }

    }

    /// <summary>

    /// Policy 策略 规范

    /// </summary>

    /// <typeparam name="T"></typeparam>

    public interface ITargetClassPolicy<T>

    {

        T Create();

        bool Return(T obj);

    }

    /// <summary>

    /// Policy 具体策略类

    /// </summary>

    /// <typeparam name="T"></typeparam>

    public class TargetClassPolicy<T> : ITargetClassPolicy<T> where T : class, new()

    {

        public T Create()

        {

            return new T();

        }

        public bool Return(T obj)

        {

            return true;

        }

    }

    class User

    {

        public string Name { get; set; }

        public int Age { get; set; }

    }

    class Program

    {

        static void Main(string[] args)

        {

            var target = new TargetClass<User>(new TargetClassPolicy<User>());

            var get = target.Get();

            Console.WriteLine($"{get.Name},{get.Age}");

            var user1 = new User()

            {

                Age = 18,

                Name = "MicroHeart"

            };

            var user2 = new User()

            {

                Age = 19,

                Name = "MicroHeart"

            };

            var user3 = new User()

            {

                Age = 20,

                Name = "MicroHeart"

            };

            target.Return(user1);

            target.Return(user2);

            target.Return(user3);

            var get1 = target.Get();

            Console.WriteLine($"{get1.Name},{get1.Age}");

            var get2 = target.Get();

            Console.WriteLine($"{get2.Name},{get2.Age}");

            Console.Read();

        }

    }

}

存储对象的数组ObjectWrapper内元素的取、还操作通过Interlock.CompareExchange巧妙的实现，并且是线程安全的。

取操作：Interlocked.CompareExchange(ref items[i].Element, null,item)。取完后将元素置为null

还操作：Interlocked.CompareExchange(ref items[i].Element, obj, null)如果元素为null，则赋值

设计原理：通过Policy构建Provider，通过Provider创建最终的目标类(target)。

参考链接：ObjectPool 对象池设计模式

巴特西

Provider模式应用demo

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