设计模式（19）---职责链模式

2019-11-14 16:17:50

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来源：转载

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一、定义

职责链模式：使得多个对象都有机会处理请求，从而避免请求的发送者和接受者之间的耦合关系。将这个对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止。

解释：简单来说应该是对于一个请求，不同的人根据自己职责范围对它进行处理，同时也因为它一般是从底层向上层传递的请求的，所以将处理该请求的不同的对象比喻成一个链，从相对“低”的地方传递到相对“高”的地方，从而完成请求操作。

二、UML类图及基本代码

基本代码：

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}处理请求{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}处理请求{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}处理请求{1}", this.GetType().Name, request);            }            else if (successor != null)            {                successor.HandleRequest(request);            }        }    }

客户端调用及其结果：

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、具体实例

列举一个能更加说明职责链的实例。john在单位，向领导请假，小于等于2天经理有权利批准，小于等于5天总监有权利批准，其他的则要交到总经理那里批准。具体代码如下：

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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客户端调用及结果：

CommonManager jinli = new CommonManager("经理");            Majordome zongjian = new Majordome("总监");            GeneralManager zhongjingli = new GeneralManager("总经理");            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);