Java Web 设计模式之开闭原则

浏览数：29 / 时间：2015年06月08日

1.开闭原则(OCP)

遵循开闭原则设计出的模块具有两个主要特征：

（1）对于扩展是开放的（Open for extension）。这意味着模块的行为是可以扩展的。当应用的需求改变时，我们可以对模块进行扩展，使其具有满足那些改变的新行为。也就是说，我们可以改变模块的功能。

（2）对于修改是关闭的（Closed for modification）。对模块行为进行扩展时，不必改动模块的源代码或者二进制代码。模块的二进制可执行版本，无论是可链接的库、DLL或者.EXE文件，都无需改动。

2.通过UML认识OCP

3.代码

(1)IShoe接口

1 package com.alibaba.www.miao;
2 
3 public interface IShoe {
4     
5     public String getName();
6     public String getType();
7     public int getValue();
8 }

View Code

(2)MenShoe实现IShoe接口

 1 package com.alibaba.www.miao;
 2 
 3 public class MenShoe implements IShoe {
 4 
 5     private String name;
 6     private String type;
 7     private int value;
 8 
 9     public MenShoe(String name, String type, int value) {
10         super();
11         this.name = name;
12         this.type = type;
13         this.value = value;
14     }
15 
16     @Override
17     public String getName() {
18         return this.name;
19     }
20 
21     @Override
22     public String getType() {
23         return this.type;
24     }
25 
26     @Override
27     public int getValue() {
28         return this.value;
29     }
30 
31 }

View Code

(3)GirlShoe实现IShoe接口

 1 package com.alibaba.www.miao;
 2 
 3 public class GirlShoe implements IShoe {
 4 
 5     private String name;
 6     private String type;
 7     private int value;
 8     
 9     public GirlShoe(String name, String type, int value) {
10         super();
11         this.name = name;
12         this.type = type;
13         this.value = value;
14     }
15 
16     @Override
17     public String getName() {
18         return this.name;
19     }
20 
21     @Override
22     public String getType() {
23         return this.type;
24     }
25 
26     @Override
27     public int getValue() {
28         return this.value;
29     }
30 
31 }

View Code

(4)PriceCutMenShoe继承MenShoe类

 1 package com.alibaba.www.miao;
 2 
 3 public class PriceCutMenShoe extends MenShoe {
 4 
 5     public PriceCutMenShoe(String name, String type, int value) {
 6         super(name, type, value);
 7     }
 8 
 9     public int getValue() {
10         int primeCost = super.getValue();
11         int cutPrice = 0;
12         if (primeCost > 200) {
13             cutPrice = cutPrice * 80 / 100;
14         }
15         if (primeCost > 150) {
16             cutPrice = cutPrice * 85 / 100;
17         }
18         return cutPrice;
19     }
20 }

View Code

(5)PriceCutGirlShoe继承GirlShoe类

 1 package com.alibaba.www.miao;
 2 
 3 public class PriceCutGirlShoe extends GirlShoe {
 4 
 5     public PriceCutGirlShoe(String name, String type, int value) {
 6         super(name, type, value);
 7     }
 8 
 9     public int getValue() {
10         int primeCost = super.getValue();
11         int cutPrice = 0;
12         if (primeCost > 200) {
13             cutPrice = cutPrice * 75 / 100;
14             System.out.println("如果原价大于200元，则打折7.5折");
15         }
16         if (primeCost > 150) {
17             cutPrice = cutPrice * 80 / 100;
18             System.out.println("如果原价大于150元，则打折8折");
19         } else {
20             cutPrice = cutPrice * 85 / 100;
21             System.out.println("其他。则打8.5折");
22         }
23         return primeCost;
24     }
25 }

View Code

(6)测试ocp.jsp，验证开闭原则

 1 <%@page import="com.alibaba.www.miao.PriceCutGirlShoe"%>
 2 <%@ page language="java" contentType="text/html; charset=UTF-8"
 3     pageEncoding="UTF-8"%>
 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 5 <html>
 6 <head>
 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 8 <title>Insert title here</title>
 9 </head>
10 <body>
11     
12     <%
13         PriceCutGirlShoe a = new PriceCutGirlShoe("女鞋名","女鞋类型",160);
14         out.print("鞋价为:"+a.getValue());
15     %>
16     
17 </body>
18 </html>