职责链模式(Chain of Responsibility)

重要概念

1. 使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。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。

2.请求是沿着链条传递到有一个处理点对象负责处理这个请求为止。请求者无需关心谁会处理这个请求。

3. 接收者和发送者都没有对方的明确信息，且链中的对象自己也并不知道链的结构。结果是职责链可简化对象的相互连接，他们仅需保持一个指向其后继者的引用，而不需要保持它所有的候选接收者的引用。

4. 从执行流程上感觉和 case break 相似。

5. 随时地增加或修改该处理一个请求的结构（处理顺序，处理点数量），增强了给对象指派职责的灵活性。

6. 解决大量分支判断造成的难维护，灵活性差的问题。

示例程序

using System;
using System.Collections.Generic;
using System.Text;

namespace 职责链模式
{
    class Program
    {
        static void Main(string[] args)
        {
            //初始化三个职责链处理点
            Handler h1 = new ConcreteHandler1();
            Handler h2 = new ConcreteHandler2();
            Handler h3 = new ConcreteHandler3();
            //设置职责链的连接处理顺序
            h1.SetSuccessor(h2);
            h2.SetSuccessor(h3);

            int[] requests = { 2, 5, 14, 22, 18, 3, 27, 20 };

            foreach (int request in requests)
            {
                //要从职责链的最小端，也就是开始的那头发出请求。
                h1.HandleRequest(request);
            }

            Console.Read();

        }
    }

    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);
            }
        }
    }

}

加薪代码2

using System;
using System.Collections.Generic;
using System.Text;

namespace 职责链模式
{
    class Program
    {
        static void Main(string[] args)
        {

            CommonManager jinli = new CommonManager("金利");
            Majordomo zongjian = new Majordomo("宗剑");
            GeneralManager zhongjingli = new GeneralManager("钟精励");
            jinli.SetSuperior(zongjian);
            zongjian.SetSuperior(zhongjingli);

            Request request = new Request();
            request.RequestType = "请假";
            request.RequestContent = "小菜请假";
            request.Number = 1;
            jinli.RequestApplications(request);

            Request request2 = new Request();
            request2.RequestType = "请假";
            request2.RequestContent = "小菜请假";
            request2.Number = 4;
            jinli.RequestApplications(request2);

            Request request3 = new Request();
            request3.RequestType = "加薪";
            request3.RequestContent = "小菜请求加薪";
            request3.Number = 500;
            jinli.RequestApplications(request3);

            Request request4 = new Request();
            request4.RequestType = "加薪";
            request4.RequestContent = "小菜请求加薪";
            request4.Number = 1000;
            jinli.RequestApplications(request4);

            Console.Read();

        }
    }

    //管理者
    abstract class Manager
    {
        protected string name;
        //管理者的上级
        protected Manager superior;

        public Manager(string name)
        {
            this.name = name;
        }

        //设置管理者的上级
        public void SetSuperior(Manager superior)
        {
            this.superior = superior;
        }

        //申请请求
        abstract public void RequestApplications(Request request);
    }

    //经理
    class CommonManager : Manager
    {
        public CommonManager(string name)
            : base(name)
        { }
        public override void RequestApplications(Request request)
        {

            if (request.RequestType == "请假" && request.Number <= 2)
            {
                Console.WriteLine("{0}:{1} 数量{2} 被批准", name, request.RequestContent, request.Number);
            }
            else
            {
                if (superior != null)
                    superior.RequestApplications(request);
            }

        }
    }

    //总监
    class Majordomo : Manager
    {
        public Majordomo(string name)
            : base(name)
        { }
        public override void RequestApplications(Request request)
        {

            if (request.RequestType == "请假" && request.Number <= 5)
            {
                Console.WriteLine("{0}:{1} 数量{2} 被批准", name, request.RequestContent, request.Number);
            }
            else
            {
                if (superior != null)
                    superior.RequestApplications(request);
            }

        }
    }

    //总经理
    class GeneralManager : Manager
    {
        public GeneralManager(string name)
            : base(name)
        { }
        public override void RequestApplications(Request request)
        {

            if (request.RequestType == "请假")
            {
                Console.WriteLine("{0}:{1} 数量{2} 被批准", name, request.RequestContent, request.Number);
            }
            else if (request.RequestType == "加薪" && request.Number <= 500)
            {
                Console.WriteLine("{0}:{1} 数量{2} 被批准", name, request.RequestContent, request.Number);
            }
            else if (request.RequestType == "加薪" && request.Number > 500)
            {
                Console.WriteLine("{0}:{1} 数量{2} 再说吧", name, request.RequestContent, request.Number);
            }
        }
    }

    //申请
    class Request
    {
        //申请类别
        private string requestType;
        public string RequestType
        {
            get { return requestType; }
            set { requestType = value; }
        }

        //申请内容
        private string requestContent;
        public string RequestContent
        {
            get { return requestContent; }
            set { requestContent = value; }
        }

        //数量
        private int number;
        public int Number
        {
            get { return number; }
            set { number = value; }
        }
    }


}