设计模式之工厂模式

最新推荐文章于 2025-05-01 17:40:29 发布

hanjiangb

最新推荐文章于 2025-05-01 17:40:29 发布

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分类专栏：设计模式文章标签：设计模式 java

本文链接：https://blog.youkuaiyun.com/hanjiangb/article/details/113767767

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案例

披萨项目：要便于披萨种类的扩展，要便于维护

披萨的种类很多（比如GreekPizz，CheesePizz等）
披萨的制作有prepare，bake，cut，box
完成披萨店订购功能
设计如下图

public abstract class Pizza {
    protected String name;

    /**
     * 准备原材料，不同的披萨不一样
     */
    public abstract void prepare();

    public void cut() {
        System.out.println(name + "cutting");
    }

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

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

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

public class CheesePizza extends Pizza {

    @Override
    public void prepare() {
        System.out.println("制作奶酪披萨，准备原材料中");
    }
}

public class GreekPizza extends Pizza {
    @Override
    public void prepare() {
        System.out.println("给希腊披萨准备原材料中");
    }
}

public class PepperPizza extends Pizza {
    @Override
    public void prepare() {
        System.out.println("给胡椒披萨准备原材料");
    }
}

public class OrderPizza {
    public OrderPizza() {
        Pizza pizza = null;
        String orderType;//订购披萨的类型
        do {
            orderType = getType();
            if (orderType.equals("greek")) {
                pizza = new GreekPizza();
                pizza.setName(" greek ");
            } else if (orderType.equals("cheese")) {
                pizza = new CheesePizza();
                pizza.setName(" cheese ");
            } else if (orderType.equals("pepper")){
                pizza = new PepperPizza();
                pizza.setName(" pepper ");
            } else {
                break;
            }
            pizza.prepare();
            pizza.bake();
            pizza.cut();
            pizza.box();
        } while (true);
    }

    private String getType() {
        try {
            BufferedReader strin = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("input pizza type");
            String str = strin.readLine();
            return str;
        } catch (Exception e) {
            System.out.println(e.getMessage());
            return "";
        }
    }
}

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

改进的思路分析

分析：修改代码可以接受，但是如果我们在其他地方也有创建pizza代码，就意味着也需要修改，而创建Pizza的代码往往有多处
思路：把创建Pizza对象封装到一个类中，这样我们有新的Pizza种类时，只需要修改该类就可以了，其他有创建到Pizza对象的代码就不需要修改了->简单工厂模式

简单工厂模式

public abstract class Pizza {
    protected String name;

    /**
     * 准备原材料，不同的披萨不一样
     */
    public abstract void prepare();

    public void cut() {
        System.out.println(name + "cutting");
    }

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

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

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

public class CheesePizza extends Pizza {

    @Override
    public void prepare() {
        System.out.println("制作奶酪披萨，准备原材料中");
    }
}

public class GreekPizza extends Pizza {
    @Override
    public void prepare() {
        System.out.println("给希腊披萨准备原材料中");
    }
}

public class PepperPizza extends Pizza {
    @Override
    public void prepare() {
        System.out.println("给胡椒披萨准备原材料");
    }
}

public class SimpleFactory {
    public Pizza createPizza(String orderType){
        System.out.println("使用简单工厂模式");
        Pizza pizza = null;
        if (orderType.equals("greek")) {
            pizza = new GreekPizza();
            pizza.setName(" greek ");
        } else if (orderType.equals("cheese")) {
            pizza = new CheesePizza();
            pizza.setName(" cheese ");
        } else if (orderType.equals("pepper")){
            pizza = new PepperPizza();
            pizza.setName(" pepper ");
        }
        return pizza;
    }
}

public class OrderPizza {
    SimpleFactory simpleFactory;
    Pizza pizza = null;

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

    public void setFactory(SimpleFactory simpleFactory) {
        String orderType = "";
        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 ");
                break;
            }
        } while (true);
    }

    private String getType() {
        try {
            BufferedReader strin = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("input pizza type");
            String str = strin.readLine();
            return str;
        } catch (Exception e) {
            System.out.println(e.getMessage());
            return "";
        }
    }
}

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

改进后的效果

当新增一种pizza类型时，只需要新增一个类，和SimpleFactory需要多写一个判断并且添加一个类型就够了，这样我们其他想创建pizza对象实例的时候，直接用SimpleFactory的create方法即可，整体代码可以有更好的方式（例如工厂内可以用枚举类判断加+反射创建类，），我这里只阐述简单工厂的思想。

工厂方法模式

介绍

工厂方法模式设计方案：将披萨项目的实例化功能抽象成抽象方法，在不同的口味点餐子类中去实现。
工厂方法模式：定义了一个创建对象的抽象方法，由子类决定要实例化的类。工厂方法模式将对象的实例化推迟到子类

public abstract class Pizza {
    protected String name;

    /**
     * 准备原材料，不同的披萨不一样
     */
    public abstract void prepare();

    public void cut() {
        System.out.println(name + "cutting");
    }

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

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

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

public class LDPepperPizza extends Pizza {
    @Override
    public void prepare() {
        setName("伦敦的胡椒pizza");
        System.out.println(" 伦敦的胡椒pizza 准备原材料 ");
    }
}

public class LDCheesePizza extends Pizza {
    @Override
    public void prepare() {
        setName("伦敦的奶酪pizza");
        System.out.println(" 伦敦的奶酪pizza 准备原材料 ");
    }
}

public class BJPepperPizza extends Pizza {
    @Override
    public void prepare() {
        setName("北京的胡椒pizza");
        System.out.println(" 北京的胡椒pizza 准备原材料 ");
    }
}

public class BJCheesePizza extends Pizza {
    @Override
    public void prepare() {
        setName("北京的奶酪pizza");
        System.out.println(" 北京的奶酪pizza 准备原材料 ");
    }
}

public abstract class OrderPizza {
    /**
     * 定义一个抽象方法，让各个工厂子类自己实现
     * @param orderType
     * @return
     */
    abstract Pizza createPizza(String orderType);

    public OrderPizza() {
        String orderType;
        Pizza pizza;
        do {
            orderType = getType();
            pizza = createPizza(orderType);
            if (pizza != null) {
                pizza.prepare();
                pizza.bake();
                pizza.cut();
                pizza.box();
            } else {
                System.out.println(" 订购失败 ");
                break;
            }
        } while (true);
    }

    private String getType() {
        try {
            BufferedReader strin = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("input pizza type");
            String str = strin.readLine();
            return str;
        } catch (Exception e) {
            System.out.println(e.getMessage());
            return "";
        }
    }
}

public class LDOrderPizza extends OrderPizza {
    @Override
    Pizza createPizza(String orderType) {
        Pizza pizza = null;
        if (orderType.equals("pepper")) {
            pizza = new LDPepperPizza();
            pizza.setName(" greek ");
        } else if (orderType.equals("cheese")) {
            pizza = new LDCheesePizza();
            pizza.setName(" cheese ");
        }
        return pizza;
    }
}

public class BJOrderPizza extends OrderPizza {
    @Override
    Pizza createPizza(String orderType) {
        Pizza pizza = null;
        if (orderType.equals("pepper")) {
            pizza = new BJPepperPizza();
            pizza.setName(" greek ");
        } else if (orderType.equals("cheese")) {
            pizza = new BJCheesePizza();
            pizza.setName(" cheese ");
        }
        return pizza;
    }
}

public class PizzaStore {
    public static void main(String[] args) {
        new BJOrderPizza();//这里new哪个就是当地的创建形式
    }
}

抽象工厂模式

基本介绍

定义了一个interface用于创建相关或有依赖关系的对象簇，而无需指明具体的类
抽象工厂模式可以将简单工厂模式和工厂方法模式进行整合
从设计层面看，抽象工厂模式就是对简单工厂模式的改进
将工厂抽象为两层，AbsFactory和具体实现的工厂子类。我们可以根据创建对象类型使用对应的工厂子类。这样讲单个的简单工厂类变成了工厂簇，更利于代码的维护和扩展

public abstract class Pizza {
    protected String name;

    /**
     * 准备原材料，不同的披萨不一样
     */
    public abstract void prepare();

    public void cut() {
        System.out.println(name + "cutting");
    }

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

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

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

public class LDPepperPizza extends Pizza {
    @Override
    public void prepare() {
        setName("伦敦的胡椒pizza");
        System.out.println(" 伦敦的胡椒pizza 准备原材料 ");
    }
}

public class LDCheesePizza extends Pizza {
    @Override
    public void prepare() {
        setName("伦敦的奶酪pizza");
        System.out.println(" 伦敦的奶酪pizza 准备原材料 ");
    }
}

public class BJPepperPizza extends Pizza {
    @Override
    public void prepare() {
        setName("北京的胡椒pizza");
        System.out.println(" 北京的胡椒pizza 准备原材料 ");
    }
}

public class BJCheesePizza extends Pizza {
    @Override
    public void prepare() {
        setName("北京的奶酪pizza");
        System.out.println(" 北京的奶酪pizza 准备原材料 ");
    }
}

public interface AbsFactory {
    /**
     * 创建披萨，让下面的工厂子类自己实现
     *
     * @param orderType
     * @return
     */
    Pizza createPizza(String orderType);
}

public class BJFactory implements AbsFactory {
    public Pizza createPizza(String orderType) {
        Pizza pizza = null;
        if (orderType.equals("cheese")) {
            pizza = new BJCheesePizza();
        } else if (orderType.equals("pepper")) {
            pizza = new BJPepperPizza();
        }
        return pizza;
    }
}

public class LDFactory implements AbsFactory {
    public Pizza createPizza(String orderType) {
        Pizza pizza = null;
        if (orderType.equals("cheese")) {
            pizza = new LDCheesePizza();
        } else if (orderType.equals("pepper")) {
            pizza = new LDPepperPizza();
        }
        return pizza;
    }
}

public class OrderPizza {
    AbsFactory factory;

    public OrderPizza(AbsFactory factory){
        setFactory(factory);
    }

    private void setFactory(AbsFactory factory){
        Pizza pizza;
        this.factory = factory;
        String orderType;
        do {
            orderType = getType();
            pizza = factory.createPizza(orderType);
            if (pizza != null) {
                pizza.prepare();
                pizza.bake();
                pizza.cut();
                pizza.box();
            } else {
                System.out.println(" 订购失败 ");
                break;
            }
        } while (true);
    }

    private String getType() {
        try {
            BufferedReader strin = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("input pizza type");
            String str = strin.readLine();
            return str;
        } catch (Exception e) {
            System.out.println(e.getMessage());
            return "";
        }
    }
}

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

小结

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管理和维护，达到和主项目的依赖关系解耦。从而提高项目的扩展性和维护性
三种工厂模式（简单工厂模式、工厂方法模式、抽象工厂模式）
设计模式的依赖抽象原则