設計模式（19）---職責鏈模式

2019-11-14 16:17:50

字體：大中小

來源：轉載

供稿：網友

一、定義

職責鏈模式：使得多個對象都有機會處理請求，從而避免請求的發送者和接受者之間的耦合關系。將這個對象連成一條鏈，并沿著這條鏈傳遞該請求，直到有一個對象處理它為止。

解釋：簡單來說應該是對于一個請求，不同的人根據自己職責范圍對它進行處理，同時也因為它一般是從底層向上層傳遞的請求的，所以將處理該請求的不同的對象比喻成一個鏈，從相對“低”的地方傳遞到相對“高”的地方，從而完成請求操作。

二、UML類圖及基本代碼

基本代碼：

abstract class Handler    {        PRotected Handler successor;        public void SetSuccessor(Handler successor)        {            this.successor = successor;        }        public abstract void HandleRequest(int request);    }    class ConcreteHandler1 : Handler    {        public override void HandleRequest(int request)        {            if (request >= 0 && request < 10)            {                Console.WriteLine("{0}處理請求{1}", this.GetType().Name, request);            }            else if (successor != null)            {                successor.HandleRequest(request);            }        }    }    class ConcreteHandler2 : Handler    {        public override void HandleRequest(int request)        {            if (request >= 10 && request < 20)            {                Console.WriteLine("{0}處理請求{1}", this.GetType().Name, request);            }            else if (successor != null)            {                successor.HandleRequest(request);            }        }    }    class ConcreteHandler3 : Handler    {        public override void HandleRequest(int request)        {            if (request >= 20 && request < 30)            {                Console.WriteLine("{0}處理請求{1}", this.GetType().Name, request);            }            else if (successor != null)            {                successor.HandleRequest(request);            }        }    }

客戶端調用及其結果：

Handler h1 = new ConcreteHandler1();            Handler h2 = new ConcreteHandler2();            Handler h3 = new ConcreteHandler3();            h1.SetSuccessor(h2);            h2.SetSuccessor(h3);            int[] requests = { 6, 5, 14, 23, 18, 9, 17, 6, 26 };            foreach (int request in requests)            {                h1.HandleRequest(request);            }

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三、具體實例

列舉一個能更加說明職責鏈的實例。john在單位，向領導請假，小于等于2天經理有權利批準，小于等于5天總監有權利批準，其他的則要交到總經理那里批準。具體代碼如下：

class Request    {        public string RequestType{get;set;}        public string RequestContent{get;set;}        public int Number{get;set;}    }    abstract class Manager    {        protected string name;        protected Manager superior;        public Manager(string name)        {            this.name = name;        }        public void SetSuperior(Manager superior)        {            this.superior = superior;        }        public abstract void Requestapplications(Request request);    }    class CommonManager : Manager    {        public CommonManager(string name)            : base(name)        { }        public override void RequestApplications(Request request)        {            if (request.RequestType == "leave" && request.Number <= 2)            {                Console.WriteLine("{0}:{1} number is {2} ok", name, request.RequestContent, request.Number);            }            else            {                if (superior != null)                {                    superior.RequestApplications(request);                }            }        }    }    class Majordome : Manager    {        public Majordome(string name)            : base(name)        { }        public override void RequestApplications(Request request)        {            if (request.RequestType == "leave" && request.Number <= 5)            {                Console.WriteLine("{0}:{1} number is {2} ok", name, request.RequestContent, request.Number);            }            else            {                if (superior != null)                {                    superior.RequestApplications(request);                }            }        }    }    class GeneralManager : Manager    {        public GeneralManager(string name)            : base(name)        { }        public override void RequestApplications(Request request)        {            if (request.RequestType == "leave")            {                Console.WriteLine("{0}:{1} number is {2} ok", name, request.RequestContent, request.Number);            }            else if (request.RequestType == "add money" && request.Number <= 500)            {                Console.WriteLine("{0}:{1} number is {2} ok", name, request.RequestContent, request.Number);            }            else if (request.RequestType == "add money" && request.Number > 500)            {                Console.WriteLine("{0}:{1} number is {2} not ok", name, request.RequestContent, request.Number);            }        }    }

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客戶端調用及結果：

CommonManager jinli = new CommonManager("經理");            Majordome zongjian = new Majordome("總監");            GeneralManager zhongjingli = new GeneralManager("總經理");            jinli.SetSuperior(zongjian);            zongjian.SetSuperior(zhongjingli);            Request request = new Request();            request.RequestType = "leave";            request.RequestContent = "john ask for days";            request.Number = 2;            jinli.RequestApplications(request);            Request request2 = new Request();            request2.RequestType = "leave";            request2.RequestContent = "john ask for days";            request2.Number = 5;            jinli.RequestApplications(request2);