Java设计模式之抽象工厂模式详解

一、什么是抽象工厂模式

为创建一组相关或相互依赖的对象提供一个接口，而且无需指定他们的具体类，这称之为抽象工厂模式（Abstract Factory）。我们并不关心零件的具体实现，而是只关心接口（API）。我们仅使用该接口（API）将零件组装称为产品。

二、示例程序

1、抽象的零件:Item类

package com.as.module.abstractfactory;

/**
 * 抽象的零件
 * @author Andy
 * @date 2021/4/29 23:16
 */
public abstract class Item {
    protected String caption;

    public Item(String caption) {
        this.caption = caption;
    }

    public abstract String makeHTML();
}

2、抽象的零件:Link类

package com.as.module.abstractfactory;

/**
 * TODO
 *
 * @author Andy
 * @date 2021/4/29 23:18
 */
public abstract class Link extends Item {
    protected String url;
    public Link(String caption,String url) {
        super(caption);
        this.url = url;
    }

}

3、抽象的零件:Tray类

package com.as.module.abstractfactory;

import java.util.ArrayList;

/**
 * TODO
 *
 * @author Andy
 * @date 2021/4/29 23:20
 */
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);
    }
}

4、抽象的产品:Page类

package com.as.module.abstractfactory;

import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.ArrayList;

/**
 * 抽象的产品
 * @author Andy
 * @date 2021/4/29 23:22
 */
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(){
        String filename = title+".html";
        try {
            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();

}

5、抽象的工厂:Factory类

package com.as.module.abstractfactory;

/**
 * 抽象的工厂
 * @author Andy
 * @date 2021/4/29 23:31
 */
public abstract class Factory {
    public static Factory getFactory(String className){
        Factory factory = null;
        try {
            factory = (Factory)Class.forName(className).newInstance();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } 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);

}

6、具体的工厂:ListFactory类

package com.as.module.abstractfactory;

/**
 * 具体的工厂
 * @author Andy
 * @date 2021/4/29 23:36
 */
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 author) {
        return new ListPage(title,author);
    }
}

7、具体的零件:ListLink类

package com.as.module.abstractfactory;

/**
 * 具体的零件
 * @author Andy
 * @date 2021/4/29 23:37
 */
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";
    }

}

8、具体的零件:ListTray类

package com.as.module.abstractfactory;

import java.util.Iterator;

/**
 * TODO
 *
 * @author Andy
 * @date 2021/4/29 23:43
 */
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+"\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();
    }
}

9、具体的零件:ListPage类

package com.as.module.abstractfactory;

import java.util.Iterator;

/**
 * 具体的产品
 * @author Andy
 * @date 2021/5/4 10:42
 */
public class ListPage extends Page {

    public ListPage(String title, String author) {
        super(title, author);
    }

    @Override
    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();
    }
}

10、抽象工厂方法测试用例

package com.as.module.abstractfactory;

import java.util.List;

/**
 *
 * @author Andy
 * @date 2021/5/4 10:54
 */
public class TestAbstractFactory {

    public static void main(String[] args) {
        Factory factory = Factory.getFactory("com.as.module.abstractfactory.ListFactory");
        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 baidu = factory.createLink("Baidu","http://www.baidu.com/");
        Link google = factory.createLink("Google","http://www.google.com/");

        Tray traynews = factory.createTray("日报");
        traynews.add(people);
        traynews.add(gmw);

        Tray traysearch = factory.createTray("搜索引擎");
        traysearch.add(baidu);
        traysearch.add(google);

        Page page = factory.createPage("LinkPage","Andy");
        page.add(traynews);
        page.add(traysearch);
        page.output();

    }
}

运行结果：

三、UML

登场角色：

1、AbstractProduct(抽象产品)

AbstractProduct角色负责定义AbstractPFactory角色所生成的抽象零件和产品的接口。在示例程序中，由Link类，Tray类和Page类扮演此角色

2、AbstractFactory(抽象工厂)

AbstractFactory角色负责定义用于生成抽象产品的接口。在示例程序中，由Factory

3、Client(委托者)

Client角色仅会调用AbstractProduct角色和AbstractFactory角色来进行工作，对于具体的零件，产品，工厂一无所知。示例程序中，由具体的TestAbstractFactory 扮演此角色

4、ConcreteProduct(具体产品)

ConcreteProduct角色负责实现抽象产品角色的接口，示例程序中，由ListLink,ListTray,ListPage类扮演此角色

5、ConcreteFactory(具体工厂)

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