【GOF23设计模式】原型模式

来源：http://www.bjsxt.com/ 
一、【GOF23设计模式】_原型模式、prototype、浅复制、深复制、Cloneable接口 

浅复制

package com.test.prototype;

import java.util.Date;

/**
 * 浅复制
 */
public class Sheep implements Cloneable{//Cloneable为标记接口
    private String sname;
    private Date birthday;

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object obj = super.clone();//直接调用object对象的clone()方法
        return obj;
    }

    public Sheep() {
    }

    public Sheep(String sname, Date birthday) {
        super();
        this.sname = sname;
        this.birthday = birthday;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
}

package com.test.prototype;

import java.util.Date;
/**
 * 测试原型模式(浅复制)
 */
public class Client {
    public static void main(String[] args) throws Exception {
        Date date = new Date(3333332323L);
        Sheep s1 = new Sheep("少利", date);
        Sheep s2 = (Sheep) s1.clone();

        System.out.println(s1);
        System.out.println(s1.getSname());
        System.out.println(s1.getBirthday());
        date.setTime(332324355555555L);//浅复制：s1和s2指向同一date对象的地址，一改全改
        System.out.println(s1.getBirthday());//s1.getBirthday() == s2.getBirthday()

        s2.setSname("多利");
        System.out.println(s2);
        System.out.println(s2.getSname());
        System.out.println(s2.getBirthday());
    }
}

控制台输出：s1修改时间后，s2的也跟着改(Fri Dec 10 00:59:15 CST 12500)

com.test.prototype.Sheep@1db9742
少利
Sun Feb 08 21:55:32 CST 1970
Fri Dec 10 00:59:15 CST 12500
com.test.prototype.Sheep@647e05
多利
Fri Dec 10 00:59:15 CST 12500

深复制

package com.test.prototype;

import java.util.Date;

/**
 * 深复制
 */
public class Sheep2 implements Cloneable{//Cloneable为标记接口
    private String sname;
    private Date birthday;

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object obj = super.clone();//直接调用object对象的clone()方法

        //添加如下代码实现深复制(Deep Clone)
        Sheep2 s = (Sheep2) obj;
        s.birthday = (Date) this.birthday.clone();//属性克隆！

        return obj;
    }

    public Sheep2() {
    }

    public Sheep2(String sname, Date birthday) {
        super();
        this.sname = sname;
        this.birthday = birthday;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
}

package com.test.prototype;

import java.util.Date;
/**
 * 测试原型模式(深复制)
 */
public class Client2 {
    public static void main(String[] args) throws Exception {
        Date date = new Date(3333332323L);
        Sheep2 s1 = new Sheep2("少利", date);
        Sheep2 s2 = (Sheep2) s1.clone();

        System.out.println(s1);
        System.out.println(s1.getSname());
        System.out.println(s1.getBirthday());
        date.setTime(332324355555555L);//浅复制：s1和s2指向同一date对象的地址，一改全改
        System.out.println(s1.getBirthday());//s1.getBirthday() == s2.getBirthday()

        s2.setSname("多利");
        System.out.println(s2);
        System.out.println(s2.getSname());
        System.out.println(s2.getBirthday());
    }
}

控制台输出：s1修改时间后，s2还是最初的(Sun Feb 08 21:55:32 CST 1970)

com.test.prototype.Sheep2@1db9742
少利
Sun Feb 08 21:55:32 CST 1970
Fri Dec 10 00:59:15 CST 12500
com.test.prototype.Sheep2@647e05
多利
Sun Feb 08 21:55:32 CST 1970

二、【GOF23设计模式】_原型模式、反序列化实现深复制、效率对比、创建型模式总结 
利用序列化和反序列化技术实现深复制

package com.test.prototype;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Date;
/**
 * 原型模式(使用序列化和反序列化的方式实现深复制)
 */
public class Client3 {
    public static void main(String[] args) throws Exception {
        Date date = new Date(3333332323L);
        Sheep s1 = new Sheep("少利", date);

        System.out.println(s1);
        System.out.println(s1.getSname());
        System.out.println(s1.getBirthday());

//      Sheep s2 = (Sheep) s1.clone();
        //使用序列化和反序列化实现深复制
        //序列化
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream    oos = new ObjectOutputStream(bos);
        oos.writeObject(s1);
        byte[] bytes = bos.toByteArray();

        //反序列化
        ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
        ObjectInputStream    ois = new ObjectInputStream(bis);

        Sheep s2 = (Sheep) ois.readObject();//深复制的对象

        System.out.println("修改原型对象的属性值");
        date.setTime(332324355555555L);
        System.out.println(s1.getBirthday());

        s2.setSname("多利");
        System.out.println(s2);
        System.out.println(s2.getSname());
        System.out.println(s2.getBirthday());
    }
}

短时间大量创建对象时，原型模式和普通new方式效率测试：

package com.test.prototype;
/**
 * 测试普通new方式创建对象和clone方式创建对象的效率差异！
 * 如果需要短时间创建大量对象，并且new的过程比较耗时，则可以考虑使用原型模式！
 */
public class Client4 {

    public static void testNew(int size){
        long start = System.currentTimeMillis();
        for (int i = 0; i < size; i++) {
            Laptop t = new Laptop();
        }
        long end = System.currentTimeMillis();
        System.out.println("new的方式创建耗时：" + (end - start));
    }

    public static void testClone(int size) throws CloneNotSupportedException{
        long start = System.currentTimeMillis();
        Laptop t = new Laptop();
        for (int i = 0; i < size; i++) {
            Laptop temp = (Laptop) t.clone();
        }
        long end = System.currentTimeMillis();
        System.out.println("clone的方式创建耗时：" + (end - start));
    }

    public static void main(String[] args) throws Exception {
        testNew(1000);
        testClone(1000);
    }
}

class Laptop implements Cloneable{//笔记本电脑
    public Laptop(){
        try{
            Thread.sleep(10);//模拟创建对象耗时的过程！
        }catch(InterruptedException e){
            e.printStackTrace();
        }
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object obj = super.clone();//直接调用object对象的clone()方法
        return obj;
    }
}

控制台输出：

new的方式创建耗时：10168
clone的方式创建耗时：10

开发中的应用场景： 
原型模式很少单独出现，一般和工厂模式一起出现，通过clone的方法创建一个对象，然后由工厂方法提供给调用者。 
spring中bean的创建实际就是两种：单例模式和原型模式（原型模式需要和工厂模式搭配起来）。

创建型模式的总结：