Factory Method模式（设计模式）

父类决定实例的生成方式，但不决定要生成的具体的类，具体的处理全部交给子类负责。

将生成实例的框架和实际负责生成实例的类解耦。

从而实现不管我们需要什么样的产品和工厂，他们的实例生成方式已经由框架里面的抽象类决定了，他们只需要使用子类去实现满足不同场景需求的产品具体生成。

小案例

Factory.java

package framework;
/**
 * @Author:DarknessShadow
 * @description:工厂，用来生成产品和注册产品
 * @date 2020/5/11 13:46
 */
public abstract class Factory {

    public final Product create(String owner) {
        Product p = createProduct(owner);
        registerProduct(p);
        return p;
    }

    protected abstract Product createProduct(String owner);

    protected abstract void registerProduct(Product product);
}

Product.java

package framework;
/**
 * @Author:DarknessShadow
 * @description:产品父类
 * @date 2020/5/11 13:46
 */
public abstract class Product {
    public abstract void use();
}

IDCardFactory.java

package idcard;
import framework.Factory;
import framework.Product;
import java.util.HashMap;
import java.util.Map;
/**
 * @Author:DarknessShadow
 * @description:继承工厂类，完成IDCard类实例产生的具体生成操作
 * @date 2020/5/11 13:47
 */
public class IDCardFactory extends Factory {

    private Map<String,Integer> owners = new HashMap<>();
    private int index = 0;

    @Override
    protected Product createProduct(String owner) {
        return new IDCard(owner);
    }

    @Override
    protected void registerProduct(Product product) {
        owners.put(((IDCard) product).getOwner(), index);
        ((IDCard) product).setId(index);
        this.index  ++;
    }

    public Map<String, Integer> getOwners() {
        return owners;
    }
}

IDCard.java

package idcard;
import framework.Product;
/**
 * @Author:DarknessShadow
 * @description:IDCard类是产品Product类的子类
 * @date 2020/5/11 13:47
 */
public class IDCard extends Product {

    private String owner;
    private int id;

    IDCard(String owner) {
        System.out.println("制作" + owner + "的ID卡。");
        this.owner = owner;
    }

    @Override
    public void use() {
        System.out.println("使用" + owner + "的ID卡,所对应的编号为：" + id );
    }

    public String getOwner() {
        return owner;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }
}

Main.java

import framework.Factory;
import framework.Product;
import idcard.IDCardFactory;
/**
 * @Author:DarknessShadow
 * @description:主测试程序
 * @date 2020/5/11 13:47
 */
public class Main {
    public static void main(String[] args) {
        Factory factory = new IDCardFactory();
        Product card1 = factory.create("小明");
        Product card2 = factory.create("小红");
        Product card3 = factory.create("小话");
        card1.use();
        card2.use();
        card3.use();

    }
}