java23种设计模式——四、原型模式

源码在我的github和gitee中获取

目录

java23种设计模式—— 一、设计模式介绍

java23种设计模式—— 二、单例模式

java23种设计模式——三、工厂模式

java23种设计模式——四、原型模式

java23种设计模式——四、原型模式

这种模式是实现了一个原型接口，该接口用于创建当前对象的克隆。当直接创建对象的代价比较大时，则采用这种模式。例如，一个对象需要在一个高代价的数据库操作之后被创建。我们可以缓存该对象，在下一个请求时返回它的克隆，在需要的时候更新数据库，以此来减少数据库调用。

举个例子，就是当我们需要给电脑安装win10系统时需要去官网上下载win10系统的安装包。而安装包的大小都是很耗时的，还需要另一台电脑来操作。如果我们下载了一个安装包放在我们的u盘里，之后需要安装win10时是不是就省去了中间寻找，下载等时间呢

原型模式的克隆分为浅克隆和深克隆，Java 中的 Object 类提供了浅克隆的 clone() 方法，具体原型类只要实现 Cloneable 接口就可实现对象的浅克隆，这里的 Cloneable 接口就是抽象原型类。其代码如下

浅克隆

新建一个实体类Sheep实现Cloneable 接口，重写clone()方法

/**
 * @author codermy
 * @createTime 2020/5/14
 */
public class Sheep implements Cloneable{
    private String name;
    private int age;
    private String sex;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Sheep(String name, int age, String sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "Sheep{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                '}';
    }
    //克隆该实例，使用默认的clone方法
    @Override
    protected Object clone() throws CloneNotSupportedException {
        Sheep sheep =null;
        sheep = (Sheep)super.clone();
        return sheep;
    }
}

测试

/**
 * @author codermy
 * @createTime 2020/5/14
 */
public class Client {
    public static void main(String[] args) throws CloneNotSupportedException {
        Sheep sheep = new Sheep("tom",1,"male");
        Sheep sheep1 = (Sheep)sheep.clone();
        System.out.println(sheep.hashCode());
        System.out.println(sheep);
        System.out.println(sheep1.hashCode());
        System.out.println(sheep1);
        sheep1.setAge(2);
        System.out.println(sheep1);
        System.out.println(sheep);
    }
}

输出

1163157884
Sheep{name='tom', age=1, sex='male'}
1956725890
Sheep{name='tom', age=1, sex='male'}
Sheep{name='tom', age=2, sex='male'}
Sheep{name='tom', age=1, sex='male'}

在浅克隆中，被复制对象的所有普通成员变量都具有与原来对象相同的值，而所有的对其他对象的引用仍然指向原来的对象。也就是说，浅克隆仅仅复制所考虑的对象，不会复制它所引用的成员对象。

我们先新建一个Pearson类，作为对象属性

/**
 * @author codermy
 * @createTime 2020/7/24
 */
public class Person implements Cloneable{
    String name;

    public String getName() {
        return name;
    }

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

    public Person(){

    }
    public Person(String name){
        this.name = name;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                '}';
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

}

我们先给Sheep实体类种添加一个对象属性

/**
 * @author codermy
 * @createTime 2020/6/16
 */
public class Sheep implements Cloneable {
    private String name;
    private int age;
    private String sex;
    public Person owner;//对象引用

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Person getOwner() {
        return owner;
    }

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

    public Sheep(String name, int age, String sex, Person owner) {
        this.name = name;
        this.age = age;
        this.sex = sex;
        this.owner = owner;
    }

    @Override
    public String toString() {
        return "Sheep{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                ", owner=" + owner +
                '}';
    }

    //克隆该实例，使用默认的clone方法
    @Override
    protected Object clone() throws CloneNotSupportedException {
        Sheep sheep =null;
        sheep = (Sheep)super.clone();
        return sheep;
    }
}

测试类中测试

/**
 * @author codermy
 * @createTime 2020/6/16
 */
public class Client {
    public static void main(String[] args) throws CloneNotSupportedException {
        Person owner = new Person("马云");
        Sheep sheep = new Sheep("tom",1,"male", owner);//新建sheep类

        Sheep sheep1 = (Sheep)sheep.clone();//克隆该类
        System.out.println(sheep.hashCode() + "  " + sheep.owner.hashCode());
        System.out.println(sheep + " "+ sheep.owner);
        System.out.println(sheep1.hashCode()+ " " + sheep1.owner.hashCode());
        System.out.println(sheep1 + " " + sheep1.owner);
        sheep1.owner.setName("马化腾");
        System.out.println(sheep.owner);
        System.out.println(sheep1.owner);
    }
}

输出

1163157884  1956725890
Sheep{name='tom', age=1, sex='male', owner=Person{name='马云'}} Person{name='马云'}
356573597 1956725890
Sheep{name='tom', age=1, sex='male', owner=Person{name='马云'}} Person{name='马云'}
Person{name='马化腾'}
Person{name='马化腾'}

我们可以看出浅克隆时对象的引用仅仅是指向了原空间，而并没有复制对象。

深克隆

在深克隆中，对值类型的成员变量进行值的复制,对引用类型的成员变量也进行引用对象的复制。

自定义clone过程实现深克隆

将上面Sheep类中的clone方法改写

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Sheep sheep =null;
        sheep = (Sheep)super.clone();
        sheep.owner = (Person) sheep.owner.clone();//引用对象的克隆方法
        return sheep;
    }

测试类测试

public class Client {
    public static void main(String[] args) throws CloneNotSupportedException {
        Person owner = new Person("马云");
        Sheep sheep = new Sheep("tom",1,"male", owner);

        Sheep sheep1 = (Sheep)sheep.clone();
        System.out.println(sheep.hashCode() + "  " + sheep.owner.hashCode());
        System.out.println(sheep + " "+ sheep.owner);
        System.out.println(sheep1.hashCode()+ " " + sheep1.owner.hashCode());
        System.out.println(sheep1 + " " + sheep1.owner);
        sheep1.owner.setName("马化腾");
        System.out.println(sheep.owner);
        System.out.println(sheep1.owner);
    }
}

输出

1163157884  1956725890
Sheep{name='tom', age=1, sex='male', owner=Person{name='马云'}} Person{name='马云'}
356573597 1735600054
Sheep{name='tom', age=1, sex='male', owner=Person{name='马云'}} Person{name='马云'}
Person{name='马云'}
Person{name='马化腾'}

这时候我们已经实现了深克隆，但是总觉得有点“浅浅克隆”的意思，如果person类中还有对象引用那不就是。。

禁止套娃

序列化实现深克隆

两个实体类实现序列化接口

Person类

public class Person implements Serializable {
    String name;

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                '}';
    }

    public Person(String name){
        this.name = name;
    }

}

Sheep类

/**
 * @author codermy
 * @createTime 2020/6/16
 */
public class Sheep implements  Serializable {
    private String name;
    private int age;
    private String sex;
    public Person owner;//对象引用

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Person getOwner() {
        return owner;
    }

    public void setOwner(Person owner) {
        this.owner = owner;
    }
    public Sheep() {
    }
    public Sheep(String name, int age, String sex, Person owner) {
        this.name = name;
        this.age = age;
        this.sex = sex;
        this.owner = owner;
    }

    @Override
    public String toString() {
        return "Sheep{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                ", owner=" + owner +
                '}';
    }

}

实现

**
 * @author codermy
 * @createTime 2020/7/24
 */
public class Client {
    public static void main(String[] args) throws Exception {
        Person owner = new Person("马云");
        Sheep sheep = new Sheep("tom",1,"male", owner);
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(sheep);
        ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()));
        Sheep sheep1 =(Sheep) ois.readObject();
        bos.flush();oos.flush();
        bos.close();oos.close();
        ois.close();
        System.out.println("Sheep: " + sheep);
        System.out.println("Sheep1: " + sheep1);
        System.out.println("================================");
        System.out.println("Sheep: " + sheep.hashCode() + "++++++++++" + sheep.owner.hashCode());
        System.out.println("Sheep1: " + sheep1.hashCode() + "++++++++++" + sheep1.owner.hashCode());
        System.out.println("================================");
        sheep1.owner.setName("马化腾");
        System.out.println("Sheep: " + sheep.owner);
        System.out.println("Sheep1: " + sheep1.owner);
    }
}

输出

1163157884  1956725890
Sheep{name='tom', age=1, sex='male', owner=Person{name='马云'}} Person{name='马云'}
356573597 1735600054
Sheep{name='tom', age=1, sex='male', owner=Person{name='马云'}} Person{name='马云'}
Person{name='马云'}
Person{name='马化腾'}

原型模式的优缺点

优点：原型模式是在内存中二进制流的拷贝，要比new一个对象的性能要好，特别是需要产生大量对象时。

缺点：直接在内存中拷贝，构造函数是不会执行的。