设计模式（八）-抽象工厂模式（Abstract Factory Pattern）——将关联零件组装诚产品

r囧r小猫 2022-06-01 10:19 36阅读 0赞

抽象工厂的工作是将“抽象零件”组装为“抽象产品”。

抽象工厂模式（Abstract Factory Pattern）不关心零件的具体实现，而是只关心接口（API）。仅使用该接口（API）将零件组装成为产品。

抽象工厂模式中，子类负责方法的具体实现，子类这一层有具体的工厂，他负责将具体的零件组装成为具体的产品。

**Item.java**

package com.test.dp.AbstractFactory.Sample.factory;
    
    //抽象零件类，Link与Tray的父类
    public abstract class Item {
        protected String caption;
        public Item(String caption) {
            this.caption = caption;
        }
        public abstract String makeHTML();
    }

**Link.java**

package com.test.dp.AbstractFactory.Sample.factory;
    
    //抽象零件类，表示Html的超链接的类
    public abstract class Link extends Item {
        protected String url;
        public Link(String caption, String url) {
            super(caption);
            this.url = url;
        }
    }

**Tray.java**

package com.test.dp.AbstractFactory.Sample.factory;
    
    import java.util.ArrayList;
    
    //抽象零件类
    public abstract class Tray extends Item {
        protected ArrayList tray = new ArrayList();
        public Tray(String caption) {
            super(caption);
        }
        public void add(Item item) {
            tray.add(item);
        }
    }

**Page.java**

package com.test.dp.AbstractFactory.Sample.factory;
    import java.io.*;
    import java.util.ArrayList;
    
    //抽象的Html页面类
    public abstract class Page {
        protected String title;
        protected String author;
        protected ArrayList content = new ArrayList();
        public Page(String title, String author) {
            this.title = title;
            this.author = author;
        }
        public void add(Item item) {
            content.add(item);
        }
        public void output() {
            try {
                String filename = title + ".html";
                Writer writer = new FileWriter(filename);
                writer.write(this.makeHTML());
                writer.close();
                System.out.println(filename + " 编写完成。");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        public abstract String makeHTML();
    }

**Factory.java**

package com.test.dp.AbstractFactory.Sample.factory;
    
    //抽象的工厂类
    public abstract class Factory {
        public static Factory getFactory(String classname) {
            Factory factory = null;
            try {
                factory = (Factory)Class.forName(classname).newInstance();//动态读取类的实例，获取类信息
            } catch (ClassNotFoundException e) {
                System.err.println("没有找到 " + classname + "类。");
            } catch (Exception e) {
                e.printStackTrace();
            }
            return factory;
        }
        public abstract Link createLink(String caption, String url);
        public abstract Tray createTray(String caption);
        public abstract Page createPage(String title, String author);
    }

第一种产品：

**ListLink.java**

package com.test.dp.AbstractFactory.Sample.listfactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    
    //零件类
    public class ListLink extends Link {
        public ListLink(String caption, String url) {
            super(caption, url);
        }
        public String makeHTML() {
            return "  <li><a href=\"" + url + "\">" + caption + "</a></li>\n";
        }
    }

**ListTray.java**

package com.test.dp.AbstractFactory.Sample.listfactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    import java.util.Iterator;
    
    //零件类
    public class ListTray extends Tray {
        public ListTray(String caption) {
            super(caption);
        }
        public String makeHTML() {
            StringBuffer buffer = new StringBuffer();
            buffer.append("<li>\n");
            buffer.append(caption + "\n");
            buffer.append("<ul>\n");
            Iterator it = tray.iterator();
            while (it.hasNext()) {
                Item item = (Item)it.next();
                buffer.append(item.makeHTML());
            }
            buffer.append("</ul>\n");
            buffer.append("</li>\n");
            return buffer.toString();
        }
    }

**ListPage.java**

package com.test.dp.AbstractFactory.Sample.listfactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    import java.util.Iterator;
    
    //页面类
    public class ListPage extends Page {
        public ListPage(String title, String author) {
            super(title, author);
        }
        public String makeHTML() {
            StringBuffer buffer = new StringBuffer();
            buffer.append("<html><head><title>" + title + "</title></head>\n");
            buffer.append("<body>\n");
            buffer.append("<h1>" + title + "</h1>\n");
            buffer.append("<ul>\n");
            Iterator it = content.iterator();
            while (it.hasNext()) {
                Item item = (Item)it.next();
                buffer.append(item.makeHTML());
            }
            buffer.append("</ul>\n");
            buffer.append("<hr><address>" + author + "</address>");
            buffer.append("</body></html>\n");
            return buffer.toString();
        }
    }

**ListFactory.java**

package com.test.dp.AbstractFactory.Sample.listfactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    
    //工厂类
    public class ListFactory extends Factory {
        public Link createLink(String caption, String url) {
            return new ListLink(caption, url);
        }
        public Tray createTray(String caption) {
            return new ListTray(caption);
        }
        public Page createPage(String title, String author) {
            return new ListPage(title, author);
        }
    }

**第二种产品：**

**TableLink.java**

package com.test.dp.AbstractFactory.Sample.tablefactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    
    //零件类
    public class TableLink extends Link {
        public TableLink(String caption, String url) {
            super(caption, url);
        }
        public String makeHTML() {
            return "<td><a href=\"" + url + "\">" + caption + "</a></td>\n";
        }
    }

**TableTray.java**

package com.test.dp.AbstractFactory.Sample.tablefactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    import java.util.Iterator;
    
    //零件类
    public class TableTray extends Tray {
        public TableTray(String caption) {
            super(caption);                     // 使用super(...)表达式  
        }
        public String makeHTML() {
            StringBuffer buffer = new StringBuffer();
            buffer.append("<td>");
            buffer.append("<table width=\"100%\" border=\"1\"><tr>");
            buffer.append("<td bgcolor=\"#cccccc\" align=\"center\" colspan=\""+ tray.size() + "\"><b>" + caption + "</b></td>");
            buffer.append("</tr>\n");
            buffer.append("<tr>\n");
            Iterator it = tray.iterator();
            while (it.hasNext()) {
                Item item = (Item)it.next();
                buffer.append(item.makeHTML());
            }
            buffer.append("</tr></table>");
            buffer.append("</td>");
            return buffer.toString();
        }
    }

**TablePage.java**

package com.test.dp.AbstractFactory.Sample.tablefactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    import java.util.Iterator;
    
    //页面类
    public class TablePage extends Page {
        public TablePage(String title, String author) {
            super(title, author);
        }
        public String makeHTML() {
            StringBuffer buffer = new StringBuffer();
            buffer.append("<html><head><title>" + title + "</title></head>\n");
            buffer.append("<body>\n");
            buffer.append("<h1>" + title + "</h1>\n");
            buffer.append("<table width=\"80%\" border=\"3\">\n");
            Iterator it = content.iterator();
            while (it.hasNext()) {
                Item item = (Item)it.next();
                buffer.append("<tr>" + item.makeHTML() + "</tr>");
            }
            buffer.append("</table>\n");
            buffer.append("<hr><address>" + author + "</address>");
            buffer.append("</body></html>\n");
            return buffer.toString();
        }
    }

**TableFactory.java**

package com.test.dp.AbstractFactory.Sample.tablefactory;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    
    //工厂实现类
    public class TableFactory extends Factory {
        public Link createLink(String caption, String url) {
            return new TableLink(caption, url);
        }
        public Tray createTray(String caption) {
            return new TableTray(caption);
        }
        public Page createPage(String title, String author) {
            return new TablePage(title, author);
        }
    }

**Main.java**

package com.test.dp.AbstractFactory.Sample;
    
    import com.test.dp.AbstractFactory.Sample.factory.*;
    
    public class Main {
        public static void main(String[] args) {
            if (args.length != 1) {
                System.out.println("Usage: java Main class.name.of.ConcreteFactory");
                System.out.println("Example 1: java Main listfactory.ListFactory");
                System.out.println("Example 2: java Main tablefactory.TableFactory");
                System.exit(0);
            }
            Factory factory = Factory.getFactory(args[0]);
    
            Link people = factory.createLink("人民日报", "http://www.people.com.cn/");
            Link gmw = factory.createLink("光明日报", "http://www.gmw.cn/");
    
            Link us_yahoo = factory.createLink("Yahoo!", "http://www.yahoo.com/");
            Link jp_yahoo = factory.createLink("Yahoo!Japan", "http://www.yahoo.co.jp/");
            Link excite = factory.createLink("Excite", "http://www.excite.com/");
            Link google = factory.createLink("Google", "http://www.google.com/");
    
            Tray traynews = factory.createTray("日报");
            traynews.add(people);
            traynews.add(gmw);
    
            Tray trayyahoo = factory.createTray("Yahoo!");
            trayyahoo.add(us_yahoo);
            trayyahoo.add(jp_yahoo);
    
            Tray traysearch = factory.createTray("检索引擎");
            traysearch.add(trayyahoo);
            traysearch.add(excite);
            traysearch.add(google);
    
            Page page = factory.createPage("LinkPage", "山外山");
            page.add(traynews);
            page.add(traysearch);
            page.output();
        }
    }

**执行结果**：略

**总结：**

**应用实例：**工作了，为了参加一些聚会，肯定有两套或多套衣服吧，比如说有商务装（成套，一系列具体产品）、时尚装（成套，一系列具体产品），甚至对于一个家庭来说，可能有商务女装、商务男装、时尚女装、时尚男装，这些也都是成套的，即一系列具体产品。假设一种情况（现实中是不存在的，要不然，没法进入共产主义了，但有利于说明抽象工厂模式），在您的家中，某一个衣柜（具体工厂）只能存放某一种这样的衣服（成套，一系列具体产品），每次拿这种成套的衣服时也自然要从这个衣柜中取出了。用 OO 的思想去理解，所有的衣柜（具体工厂）都是衣柜类的（抽象工厂）某一个，而每一件成套的衣服又包括具体的上衣（某一具体产品），裤子（某一具体产品），这些具体的上衣其实也都是上衣（抽象产品），具体的裤子也都是裤子（另一个抽象产品）。

**优点：**当一个产品族中的多个对象被设计成一起工作时，它能保证客户端始终只使用同一个产品族中的对象。

**缺点：**产品族扩展非常困难，要增加一个系列的某一产品，既要在抽象的 Creator 里加代码，又要在具体的里面加代码。

**使用场景：**1、QQ 换皮肤，一整套一起换。2、生成不同操作系统的程序。

**注意事项：**产品族难扩展，产品等级易扩展。