职责链模式

职责链模式定义

职责链模式（Chain of Responsibility），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，直到一个对象处理它为止。

职责链模式结构图

职责链模式结构图如下所示：

图 01 职责链模式结构图

职责链模式套用代码

 1 #include "iostream"
 2 using namespace std;
 3 
 4 // 定义一个处理请求的接口
 5 class Handler
 6 {
 7 protected:
 8     Handler* successor;
 9 public:
10     // 设置继任者
11     void SetSuccessor(Handler* successor)
12     {
13         this->successor = successor;
14     }
15 
16     // 处理请求的纯虚函数
17     virtual void HandleRequest(int request) = 0;
18 };
19 
20 // 处理request在0-10之间
21 class ConcreteHandler1 : public Handler
22 {
23 public:
24     virtual void HandleRequest(int request)
25     {
26         if(request >= 0 && request < 10)
27         {
28             cout << "ConcreteHandler1处理请求request = " << request << endl;
29         }
30         else if(successor != NULL)
31         {
32             successor->HandleRequest(request);
33         }
34     }
35 };
36 
37 // 处理request在10-20之间
38 class ConcreteHandler2 : public Handler
39 {
40 public:
41     virtual void HandleRequest(int request)
42     {
43         if(request >= 10 && request < 20)
44         {
45             cout << "ConcreteHandler2处理请求request = " << request << endl;
46         }
47         else if(successor != NULL)
48         {
49             successor->HandleRequest(request);
50         }
51     }
52 };
53 
54 // 处理request在20-30之间
55 class ConcreteHandler3 : public Handler
56 {
57 public:
58     virtual void HandleRequest(int request)
59     {
60         if(request >= 20 && request < 30)
61         {
62             cout << "ConcreteHandler3处理请求request = " << request << endl;
63         }
64         else if(successor != NULL)
65         {
66             // 由于这里是请求处理的末端所以这里必须要非常小心的处理，
67             // 要不然会导致死循环的
68             //successor->HandlerRequest(request);
69             cout << "到达请求末端" << endl;
70         }
71     }
72 };
73 
74 void main()
75 {
76     Handler* h1 = new ConcreteHandler1();
77     Handler* h2 = new ConcreteHandler2();
78     Handler* h3 = new ConcreteHandler3();
79     h1->SetSuccessor(h2);
80     h2->SetSuccessor(h3);
81 
82     int a[6] = {2, 5, 14, 22, 18, 33};
83     for(int i = 0; i < 6; i++)
84     {
85         h1->HandleRequest(a[i]);
86     }
87 
88     delete h1;
89     h1 = NULL;
90     
91     delete h2;
92     h3 = NULL;
93     
94     delete h3;
95     h3 = NULL;
96 }

职责链模式特点

① 当客户提交一个请求时，请求是沿链传递直到一个ConcreteHandler对象负责处理它，这样第个请求都一定会有对象进行处理

② 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想到连接，它们仅需保持一个指向其后继者的引用，而不需保持它所有的候选接受者的引用，这样大大降低了耦合度

③ 随时地增加或修改处理一个请求的结构。增强了给对象指派职责的灵活性

④ 需要注意的是：一个请求极有可能到了链的末端都得不到处理，或者因为没有正确配置而得不到处理，这就很糟糕了，需要事先考虑全面

职责链模式实例应用

职责链模式实例应用类图

图 02 职责链模式实例应用类图

职责链模式实例应用代码

  1 #include "iostream"
  2 using namespace std;
  3 #include <string>
  4 
  5 // 请求的内容
  6 class Request
  7 {
  8 private:
  9     string requestType;
 10     int number;
 11 public:
 12     string GetRequestType()
 13     {
 14         return this->requestType;
 15     }
 16     
 17     void SetRequestType(string requestType)
 18     {
 19         this->requestType = requestType;
 20     }
 21 
 22     int GetNumber()
 23     {
 24         return this->number;
 25     }
 26 
 27     void SetNumber(int number)
 28     {
 29         this->number =number;
 30     }
 31 };
 32 
 33 // 处理的接口（经理类）
 34 class Manager
 35 {
 36 protected:
 37     string name;
 38     Manager* superior;
 39 public:
 40     Manager(string name)
 41     {
 42         this->name = name;
 43     }
 44 
 45     void SetSuperior(Manager* superior)
 46     {
 47         this->superior = superior;
 48     }
 49 
 50     virtual void RequestApplications(Request* request) = 0;
 51 };
 52 
 53 // 普通的经理类
 54 class CommonManager : public Manager
 55 {
 56 public:
 57     CommonManager(string name)
 58         : Manager(name)
 59     {
 60         
 61     }
 62 
 63     virtual void RequestApplications(Request* request)
 64     {
 65         if(request->GetRequestType() == "请假" && request->GetNumber() <= 2)
 66         {
 67             cout << "  姓名 = " << name << " 请求类型 = " << request->GetRequestType(); 
 68             cout << "  数量 = "  << request->GetNumber() << "  批准" << endl; 
 69         }
 70         else
 71         {
 72             if(superior != NULL)
 73             {
 74                 superior->RequestApplications(request);
 75             }
 76         }
 77     }
 78 };
 79 
 80 // 总监
 81 class Majordomo : public Manager
 82 {
 83 public:
 84     Majordomo(string name)
 85         : Manager(name)
 86     {
 87         
 88     }
 89 
 90     virtual void RequestApplications(Request* request)
 91     {
 92         if(request->GetRequestType() == "请假" && request->GetNumber() <= 5)
 93         {
 94             cout << "  姓名 = " << name << "  请求类型 = " << request->GetRequestType();
 95             cout << "  数量 = "  << request->GetNumber() << "  批准" << endl; 
 96         }
 97         else
 98         {
 99             if(superior != NULL)
100             {
101                 superior->RequestApplications(request);
102             }
103         }
104     }
105 };
106 
107 // 总经理
108 class GeneralManager : public Manager
109 {
110 public:
111     GeneralManager(string name)
112         : Manager(name)
113     {
114         
115     }
116 
117     virtual void RequestApplications(Request* request)
118     {
119         if(request->GetRequestType() == "请假")
120         {
121             cout << "  姓名 = " << name << "  请求类型 = " << request->GetRequestType();
122             cout << "  数量 = " << request->GetNumber() << "  批准" << endl; 
123         }
124         else if(request->GetRequestType() ==  "加薪" && request->GetNumber() <= 500)
125         {
126             if(superior != NULL)
127             {
128                 cout << "  姓名 = " << name << "  请求类型 = " << request->GetRequestType();
129                 cout << "  数量 = " << request->GetNumber() << "  批准" << endl; 
130             }
131         }
132         else if(request->GetRequestType() ==  "加薪" && request->GetNumber() > 500)
133         {
134             cout << "  姓名 = " << name << "  请求类型 = " << request->GetRequestType();
135             cout << "  数量 = " << request->GetNumber() << "  加薪太高了，再讲吧" << endl;
136         }
137     }
138 };
139 
140 
141 void main()
142 {
143     CommonManager* jinli = new CommonManager("金利");
144     Majordomo* zongjian = new Majordomo("总监");
145     GeneralManager* zhongjingli = new GeneralManager("总经理");
146     jinli->SetSuperior(zongjian);
147     zongjian->SetSuperior(zhongjingli);
148 
149     Request* request1 = new Request();
150     request1->SetRequestType("请假");
151     request1->SetNumber(1);
152     jinli->RequestApplications(request1);
153     
154     Request* request2 = new Request();
155     request2->SetRequestType("请假");
156     request2->SetNumber(4);
157     jinli->RequestApplications(request2);
158     
159     Request* request3 = new Request();
160     request3->SetRequestType("加薪");
161     request3->SetNumber(400);
162     jinli->RequestApplications(request3);
163     
164     Request* request4 = new Request();
165     request4->SetRequestType("加薪");
166     request4->SetNumber(1000);
167     jinli->RequestApplications(request4);
168 
169     delete jinli;
170     jinli = NULL;
171     delete zongjian;
172     zongjian = NULL;
173     delete zhongjingli;
174     zhongjingli = NULL;
175 
176     delete request1;
177     request1 = NULL;
178     delete request2;
179     request2 = NULL;
180     delete request3;
181     request3 = NULL;
182     delete request4;
183     request4 = NULL;
184 }

2014-12-07 16:58:38

posted on 2014-12-07 16:55 xiaoheike 阅读(251) 评论(0) 收藏举报

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