设计模式2-简单工厂模式

Posted 2021-08-11 yuec1998

工厂模式的意义：
将实例化对象的代码提取出来，放到一个类中统一维护和管理，达到和主项目的依赖关系的解耦，从而提高项目的扩展和维护性。

例子1
「反例：」

String medalType = "guest";
if ("guest".equals(medalType)) {
    System.out.println("嘉宾勋章");
 } else if ("vip".equals(medalType)) {
    System.out.println("会员勋章");
} else if ("guard".equals(medalType)) {
    System.out.println("展示守护勋章");
}

…

首先，我们把每个条件逻辑代码块，抽象成一个公共的接口，我们根据每个逻辑条件，定义相对应的策略实现类，可得以下代码：

//勋章接口
public interface IMedalService {
    void showMedal();
}

//守护勋章策略实现类
public class GuardMedalServiceImpl implements IMedalService {
    @Override
    public void showMedal() {
        System.out.println("展示守护勋章");
    }
}
//嘉宾勋章策略实现类
public class GuestMedalServiceImpl implements IMedalService {
    @Override
    public void showMedal() {
        System.out.println("嘉宾勋章");
    }
}
//VIP勋章策略实现类
public class VipMedalServiceImpl implements IMedalService {
    @Override
    public void showMedal() {
        System.out.println("会员勋章");
    }
}

接下来，我们再定义策略工厂类，用来管理这些勋章实现策略类，如下：

//勋章服务工产类
public class MedalServicesFactory {

    private static final Map<String, IMedalService> map = new HashMap<>();
    static {
        map.put("guard", new GuardMedalServiceImpl());
        map.put("vip", new VipMedalServiceImpl());
        map.put("guest", new GuestMedalServiceImpl());
    }
    public static IMedalService getMedalService(String medalType) {
        return map.get(medalType);
    }
}

优化后，正例如下：

ublic class Test {
public static void main(String[] args) {
String medalType = “guest”;
IMedalService medalService = MedalServicesFactory.getMedalService(medalType);
medalService.showMedal();
}
}

例子2

public class Factory {
    public static void main(String[] args) {
        new OrderPizza(new SimpleFactory());
    }
}

//订购pizza
class OrderPizza{
    SimpleFactory simpleFactory;
    Pizza pizza;

    public OrderPizza (SimpleFactory simpleFactory){
        setFactory(simpleFactory);
    }

    public void setFactory(SimpleFactory simpleFactory){
        String orderType="";//用户输入
        this.simpleFactory = simpleFactory;
        do {
            orderType=getType();
            pizza=this.simpleFactory.createPizza(orderType);
            if (pizza!=null){
                pizza.prepare();
                pizza.bake();
                pizza.cut();
                pizza.box();
            }else {
                System.out.println("订购失败");
            }

        }while(true);
    }

    public String getType(){
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入你要订购的pizza：");
        return scanner.nextLine();
    }
}



//简单工厂
class SimpleFactory {
    Pizza pizza;
    public Pizza createPizza(String orderType) {
        if (orderType.equals("cheese")) {
            pizza = new CheesePizza();
            pizza.setName("奶酪披萨");
        }else if(orderType.equals("pepper")){
            pizza = new PepperPizza();
            pizza.setName("胡椒披萨");
        }
        return pizza;
    }
}

//芝士披萨
class CheesePizza extends Pizza {
    @Override
    public void prepare() {
        System.out.println("准备芝士");
    }
}

//胡椒披萨
class PepperPizza extends Pizza {
    @Override
    public void prepare() {
        System.out.println("准备胡椒");
    }
}

//pizza
abstract class Pizza {
    protected String name;

    //准备原材料不同的pizza，抽象方法
    public abstract void prepare();

    //烘烤
    public void bake() {
        System.out.println(name + "baking");
    }

    //切割
    public void cut() {
        System.out.println(name + "cuting");
    }

    //打包
    public void box() {
        System.out.println(name + "boxing");
    }

    public void setName(String name) {
        this.name = name;
    }
}