设计模式-抽象工厂（Abstract Factory）

时间 2019-11-11

标签设计模式抽象工厂 abstract factory 繁體版

原文原文链接

2018-1-21 by Atlashtml

设计思想

客户类和工厂类分开。消费者任什么时候候须要某套产品集合时，只需向抽象工厂请求便可。抽象工厂会再向具体的工厂生产出符合产品集规格的产品。app

应用场景

抽象替代具体，下降客户方对具体工厂的耦合，只给客户方提供接口和抽象类。
优势：下降依赖具体，下降耦合。
缺点：完工的工厂越多，新增其余零件须要的修改就越多。ide

UML 类图

AbstractProduct（抽象产品）参与者
AbstractProduct参与者规定由AbstractFactory参与者所产生的抽象零件和产品的接口。

AbstractFactory（抽象工厂）参与者
AbstractFactory参与者规定用来产生AbstractProduct参与者的对象实例的接口。

Client（客户）参与者
Client参与者是一个只使用AbstractFactory参与者和AbstractProduct参与者的接口来完成工做的参与者。Client参与者并不知道具体零件、产品和工厂。

ConcreteProduct（具体产品）参与者
ConcreteProduct参与者是AbstractProduct参与者的具体实现。

ConcreteFactory（具体工厂）参与者
ConcreteFactory参与者是AbstractFactory参与者的具体实现。

标准示例

public abstract class Item {
    protected String caption;
    public Item(String caption){
        this.caption = caption;
    }
    public abstract String makeHTML();
}
public abstract class Link extends Item {
    protected String url;
    public Link(String caption, String url){
        super(caption);
        this.url = url;
    }
}
public abstract class Tray extends Item {
    protected Vector tray = new Vector();
    public Tray(String caption){
        super(caption);
    }
    public void add(Item item){
        tray.add(item);
    }
}
public abstract class Page {
    protected String title;
    protected String autor;
    protected Vector content = new Vector();
    public Page(String title, String autor){
        this.title = title;
        this.autor = autor;
    }
    public void add(Item item){
        content.add(item);
    }
    public abstract String makeHTML();
    public void output(){
        try {
            String filename = title + ".html";
            Writer writer = new FileWriter(filename);
            writer.write(this.makeHTML());
            writer.close();
            System.out.println("已产生" + filename + "。");
        } catch (IOException e){
            e.printStackTrace();
        }
    }
}

public abstract class Factory {
    public static Factory getFactory(String className){
        Factory factory = null;
        try {
            factory = (Factory) Class.forName(className).newInstance();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (Exception ex){
            ex.printStackTrace();
        }
        return factory;
    }
    public abstract Link createLink(String caption, String url);
    public abstract Tray createTray(String caption);
    public abstract Page createPage(String title, String autor);
}

public class ListLink extends Link {
    public ListLink(String caption, String url){
        super(caption, url);
    }
    @Override
    public String makeHTML() {
        return "<li><a href=\"" + url + "\">" + caption + "</a></li>\n";
    }
}
public class ListTray extends Tray {
    public ListTray(String caption){
        super(caption);
    }
    @Override
    public String makeHTML() {
        StringBuffer buffer = new StringBuffer();
        buffer.append("<li>\n");
        buffer.append(caption).append("\n");
        buffer.append("<ul>\n");
        Iterator iterator = tray.iterator();
        while(iterator.hasNext()){
            Item item = (Item) iterator.next();
            buffer.append(item.makeHTML());
        }
        buffer.append("</ul>\n");
        buffer.append("</li>\n");
        return buffer.toString();
    }
}
public class ListPage extends Page {
    public ListPage(String title, String autor){
        super(title, autor);
    }
    @Override
    public String makeHTML() {
        StringBuffer buffer = new StringBuffer();
        buffer.append("<html><head><title>").append(title).append("</title></head>\n");
        buffer.append("<body>\n");
        buffer.append("<h1>").append(title).append("</h1>\n");
        buffer.append("<ul>\n");
        Iterator iterator = content.iterator();
        while(iterator.hasNext()){
            Item item = (Item) iterator.next();
            buffer.append(item.makeHTML());
        }
        buffer.append("</ul>\n");
        buffer.append("<hr><address>").append(autor).append("</address>");
        buffer.append("</body><html>\n");
        return buffer.toString();
    }
}

public class ListFactory extends Factory {
    @Override
    public Link createLink(String caption, String url) {
        return new ListLink(caption, url);
    }
    @Override
    public Tray createTray(String caption) {
        return new ListTray(caption);
    }
    @Override
    public Page createPage(String title, String autor) {
        return new ListPage(title, autor);
    }
}

public class Main {
    public static void main(String[] args){
        Scanner scanner=new Scanner(System.in);
        String className = scanner.next();
        Factory factory = Factory.getFactory(className);
        Link asahi = factory.createLink("朝日新闻", "http://www.asahi.com/");
        Link yomiuri = factory.createLink("读卖新闻", "http://www.yomiuri.co.jp/");
        Link us_yahoo = factory.createLink("Yahoo!", "http://www.yahoo.com/");
        Link google = factory.createLink("Google", "http://www.google.com/");
        Tray trayews = factory.createTray("新闻");
        trayews.add(asahi);
        trayews.add(yomiuri);
        Tray trayyahoo = factory.createTray("Yahoo!");
        trayyahoo.add(us_yahoo);
        Tray traysearch = factory.createTray("搜索引擎");
        traysearch.add(google);
        Page page = factory.createPage("LinkPage", "Atlas");
        page.add(trayews);
        page.add(trayyahoo);
        page.add(traysearch);
        page.output();
    }
}

抽象产品参与者是Link类、Tray类和Page类。
抽象工厂参与者是Factory类。
具体产品参与者是ListLink类、ListTray类和ListPage类。
具体工厂参与者是ListFactory类。this

案例鉴赏

搜寻中...搜索引擎