设计模式——原型模式

最新推荐文章于 2024-11-05 09:00:00 发布

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设计模式——原型模式

1原型模式的定义

原型模式：原型模式（Prototype Pattern）就是根据现有的实例生成新的实例的一种模式。在实际应用中可能对象的生成很复杂，可能对象中包含的对象太多，总之对象的生成比较复杂，此时就可以根据原型模式通过克隆的方式生成新的对象。

No BB，Show Code！

2原型模式的代码实现

2-1定义接口

定义一个继承了Cloneable的产品接口Product，在此接口中也定义了克隆生成新的对象的方法，代码如下：

package designPattern.test.prototype;

import java.io.Serializable;

/**
 * 产品接口，继承于Cloneable
 */
public interface Product extends Cloneable, Serializable {

    //使用方法
    void use(String s);

    //创建克隆对象方法
    Product createClone();
}

2-2定义具体的产品

在本例中定义了3种具体的产品实现Product接口，分别为Bike、Car、Parking，代码如下：

Bike：

package designPattern.test.prototype;

/**
 * 自行车对象
 */
public class Bike implements Product {

    private String owner;

    public String getOwner() {
        return owner;
    }

    public void setOwner(String owner) {
        this.owner = owner;
    }

    public Bike() {
    }

    public Bike(String owner) {
        this.owner = owner;
    }

    @Override
    public void use(String s) {
        System.out.println("=====Bike====" + s);
    }

    //调用clone方法并返回
    @Override
    public Product createClone() {
        Product p = null;
        try {
            p = (Product) clone();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return p;
    }

    public Object clone() {
        Object obj = null;
        try {
            obj = super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return obj;
    }
}

Car：

package designPattern.test.prototype;

/**
 * 汽车对象
 */
public class Car implements Product {

    private String owner;

    public Car() {
    }

    public Car(String owner) {
        this.owner = owner;
    }

    public String getOwner() {
        return owner;
    }

    public void setOwner(String owner) {
        this.owner = owner;
    }

    @Override
    public void use(String s) {
        System.out.println("=====Car====" + s);
    }

    //调用clone方法并返回
    @Override
    public Product createClone() {
        Product p = null;
        try {
            p = (Product) clone();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return p;
    }

    public Object clone() {
        Object obj = null;
        try {
            obj = super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return obj;
    }
}

Parking：

package designPattern.test.prototype;

import java.util.List;
import java.util.Map;

/**
 * 停车场类
 */
public class Parking implements Product {

    private String name;

    private List<Bike> bikeList;

    private List<Car> carList;

    private Map<String, Object> map;

    public String getName() {
        return name;
    }

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

    public List<Bike> getBikeList() {
        return bikeList;
    }

    public void setBikeList(List<Bike> bikeList) {
        this.bikeList = bikeList;
    }

    public List<Car> getCarList() {
        return carList;
    }

    public void setCarList(List<Car> carList) {
        this.carList = carList;
    }

    public Map<String, Object> getMap() {
        return map;
    }

    public void setMap(Map<String, Object> map) {
        this.map = map;
    }

    @Override
    public void use(String s) {
        System.out.println("-----Parking-----" + s);
    }

    @Override
    public Product createClone() {
        Product p = null;
        try {
            p = (Product) clone();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return p;
    }

    public Object clone() {
        Object obj = null;
        try {
            obj = super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return obj;
    }
}

2-3定义管理类

定义一个管理类用于管理通过克隆方式生成新对象，代码如下：

package designPattern.test.prototype;

import java.util.HashMap;
import java.util.Map;

/**
 * 管理类
 */
public class Manager {

    private Map<String, Product> productMap = new HashMap();

    //注册产品
    public void register(String name, Product product) {
        productMap.put(name, product);
    }

    //克隆出产品并返回
    public Product create(String name) {
        Product p = productMap.get(name);
        return p.createClone();
    }
}

3测试

测试代码如下：

package designPattern.test.prototype;

import com.google.common.collect.Lists;
import org.junit.Test;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.HashMap;
import java.util.Map;

/**
 * 原型模式测试
 */
public class ProtoTypeTest {

    @Test
    public void testPrototype() {
        Manager manager = new Manager();
        Bike bike1 = new Bike("小明");
        Bike bike2 = new Bike("小强");
        Bike bike3 = new Bike("小红");
        Car car1 = new Car("王总");
        Car car2 = new Car("李总");
        Car car3 = new Car("余总");
        manager.register(bike1.getOwner(), bike1);
        manager.register(bike2.getOwner(), bike1);
        manager.register(bike3.getOwner(), bike1);
        manager.register(car1.getOwner(), car1);
        manager.register(car2.getOwner(), car2);
        manager.register(car3.getOwner(), car3);
        Bike bike1Clone = (Bike) manager.create(bike1.getOwner());
        Parking parking = new Parking();
        String name = "保安";
        parking.setName(name);
        parking.setBikeList(Lists.newArrayList(bike1, bike2, bike3));
        parking.setCarList(Lists.newArrayList(car1, car2, car3));
        Map<String, Object> map = new HashMap();
        map.put("aa", "aa");
        map.put("bb", 2);
        map.put("cc", Lists.newArrayList(1.1, 2.2));
        parking.setMap(map);
        manager.register(parking.getName(), parking);
        System.out.println(bike1 == bike1Clone);
        Parking parkingClone = (Parking) manager.create("保安");
        System.out.println(parking == parkingClone);
        parking.getBikeList().add(bike1Clone);
        System.out.println(parkingClone.getBikeList().size());
        Parking parkingDeepClone = null;
        try {
            parkingDeepClone = (Parking) deepClone(parking);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(parking == parkingDeepClone);
        parking.getBikeList().remove(bike2);
        parking.getBikeList().remove(bike1);
        System.out.println(parkingDeepClone.getBikeList().size());
    }

    /**
     * 深度克隆方法:通过对象流的方式实现的深度克隆
     */
    private Product deepClone(Product product) throws Exception {
        //将对象写到流里
        ByteArrayOutputStream bo = new ByteArrayOutputStream();
        ObjectOutputStream oo = new ObjectOutputStream(bo);
        oo.writeObject(product);
        //从流里读出来
        ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());
        ObjectInputStream oi = new ObjectInputStream(bi);
        return (Product) oi.readObject();
    }
}

打印结果：

false
false
4
false
4

总结：使用原型模式需要注意的是如果没有重写clone方法的话，那么克隆就是浅克隆，即只是复制了复制了对象的引用并没有创建一个新的对象，在测试代码中通过原型模式克隆对象的方式克隆了parking得到parkingClone，但是修改parking对象的bikeList属性后，parkingClone的bikeList也变化了，可知浅克隆只是复制了引用，并没有创建新对象，而通过对象流的方式克隆则是深克隆，parkingDeepClone就是与parking完全是两个不同对象了！