【设计模式】建造模式

  1 package com.lcw.design;
  2 
  3 /**
  4  * @description：我们知道媒体可以存在不同的表达形式，比如书籍、杂志和网络。
  5  * 这个例子表示不同形式的媒体构造的步骤是相似的，所以可以被提取到指导者角色中去。
  6  * @author 刘成伟（wwwlllll@126.com）
  7  * @date Jun 25, 2014 10:04:23 PM
  8  */
  9 
 10 import java.util.ArrayList;
 11 import java.util.Arrays;
 12 import java.util.Iterator;
 13 import java.util.List;
 14 
 15 //媒体形式
 16 class Media extends ArrayList {
 17 }
 18 
 19 //不同的媒体形式:
 20 class Book extends Media {
 21 }
 22 
 23 class Magazine extends Media {
 24 }
 25 
 26 class WebSite extends Media {
 27 }
 28 
 29 //媒体构成元素
 30 class MediaItem {
 31     private String s;
 32 
 33     public MediaItem(String s) {
 34         this.s = s;
 35     }
 36 
 37     public String toString() {
 38         return s;
 39     }
 40 }
 41 
 42 //不同的媒体构成元素:
 43 class Chapter extends MediaItem {
 44     public Chapter(String s) {
 45         super(s);
 46     }
 47 }
 48 
 49 class Article extends MediaItem {
 50     public Article(String s) {
 51         super(s);
 52     }
 53 }
 54 
 55 class WebItem extends MediaItem {
 56     public WebItem(String s) {
 57         super(s);
 58     }
 59 
 60     // 抽象建造者角色，它规范了所有媒体建造的步骤:
 61     class MediaBuilder {
 62         public void buildBase() {
 63         }
 64 
 65         public void addMediaItem(MediaItem item) {
 66         }
 67 
 68         public Media getFinishedMedia() {
 69             return null;
 70         }
 71     }
 72 
 73     //具体建造者角色
 74     class BookBuilder extends MediaBuilder {
 75         private Book b;
 76 
 77         public void buildBase() {
 78             System.out.println("Building book framework");
 79             b = new Book();
 80         }
 81 
 82         public void addMediaItem(MediaItem chapter) {
 83             System.out.println("Adding chapter " + chapter);
 84             b.add(chapter);
 85         }
 86 
 87         public Media getFinishedMedia() {
 88             return b;
 89         }
 90     }
 91 
 92     class MagazineBuilder extends MediaBuilder {
 93         private Magazine m;
 94 
 95         public void buildBase() {
 96             System.out.println("Building magazine framework");
 97             m = new Magazine();
 98         }
 99 
100         public void addMediaItem(MediaItem article) {
101             System.out.println("Adding article " + article);
102             m.add(article);
103         }
104 
105         public Media getFinishedMedia() {
106             return m;
107         }
108     }
109 
110     class WebSiteBuilder extends MediaBuilder {
111         private WebSite w;
112 
113         public void buildBase() {
114             System.out.println("Building web site framework");
115             w = new WebSite();
116         }
117 
118         public void addMediaItem(MediaItem webItem) {
119             System.out.println("Adding web item " + webItem);
120             w.add(webItem);
121         }
122 
123         public Media getFinishedMedia() {
124             return w;
125         }
126     }
127 
128     //指导者角色，也叫上下文
129     class MediaDirector {
130         private MediaBuilder mb;
131 
132         public MediaDirector(MediaBuilder mb) {
133             this.mb = mb; //具有策略模式相似特征的
134         }
135 
136         public Media produceMedia(List input) {
137             mb.buildBase();
138             for (Iterator it = input.iterator(); it.hasNext();)
139                 mb.addMediaItem((MediaItem) it.next());
140             return mb.getFinishedMedia();
141         }
142     }
143 
144     //测试程序——客户程序角色
145     public class BuildMedia {
146         private List input = Arrays.asList(new MediaItem[] { new MediaItem("item1"), new MediaItem("item2"), new MediaItem("item3"), new MediaItem("item4"), });
147 
148         public void testBook() {
149             MediaDirector buildBook = new MediaDirector(new BookBuilder());
150             Media book = buildBook.produceMedia(input);
151             String result = "book: " + book;
152             System.out.println(result);
153         }
154 
155         public void testMagazine() {
156             MediaDirector buildMagazine = new MediaDirector(new MagazineBuilder());
157             Media magazine = buildMagazine.produceMedia(input);
158             String result = "magazine: " + magazine;
159             System.out.println(result);
160         }
161 
162         public void testWebSite() {
163             MediaDirector buildWebSite = new MediaDirector(new WebSiteBuilder());
164             Media webSite = buildWebSite.produceMedia(input);
165             String result = "web site: " + webSite;
166 
167             System.out.println(result);
168         }
169 
170         public void main(String[] args) {
171             BuildMedia media = new BuildMedia();
172             media.testBook();
173             media.testMagazine();
174             media.testWebSite();
175         }
176     }
177 }