10 创建型模式-原型模式

引言：
创建对象的五种方式：

1. 通过new关键字
2. 通过Class类的newInstance()方法
3. 通过Constructor类的newInstance()方法
4. 利用Clone方法
5. 反序列化

Clone方法：
其实现方式正是通过调用 Object 类的 clone() 方法来完成。

protected native Object clone() throws CloneNotSupportedException;

public class Person implements Cloneable{public String pname;public int page;public Address address;public Person() {}public Person(String pname,int page){this.pname = pname;this.page = page;this.address = new Address();}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}public void setAddress(String provices,String city ){address.setAddress(provices, city);}public void display(String name){System.out.println(name+":"+"pname=" + pname + ", page=" + page +","+ address);}public String getPname() {return pname;}public void setPname(String pname) {this.pname = pname;}public int getPage() {return page;}public void setPage(int page) {this.page = page;}}

public class Address {private String provices;private String city;public void setAddress(String provices,String city){this.provices = provices;this.city = city;}@Overridepublic String toString() {return "Address [provices=" + provices + ", city=" + city + "]";}}

这是一个我们要进行赋值的原始类 Person。下面我们产生一个 Person 对象，并调用其 clone 方法复制一个新的对象。
注意：调用对象的 clone 方法，必须要让类实现 Cloneable 接口，并且覆写 clone 方法。
测试：

@Test
public void testShallowClone() throws Exception{Person p1 = new Person("zhangsan",21);p1.setAddress("湖北省", "武汉市");Person p2 = (Person) p1.clone();System.out.println("p1:"+p1);System.out.println("p1.getPname:"+p1.getPname().hashCode());System.out.println("p2:"+p2);System.out.println("p2.getPname:"+p2.getPname().hashCode());p1.display("p1");p2.display("p2");p2.setAddress("湖北省", "荆州市");System.out.println("将复制之后的对象地址修改：");p1.display("p1");p2.display("p2");
}

深拷贝

如何实现深拷贝？

1. 让每个引用类型属性内部都重写clone() 方法
2. 利用序列化

1 原型模式介绍

定义: 原型模式(Prototype Design Pattern)用一个已经创建的实例作为原型，通过复制该原型对象来创建一个和原型对象相同的新对象。

西游记中的孙悟空 拔毛变小猴,孙悟空这种根据自己的形状复制出多个身外化身的技巧,在面向对象软件设计领域被称为原型模式.孙悟空就是原型对象.

2 原型模式原理

3 深克隆与浅克隆

3) 浅克隆代码实现：

测试

@Test
public void test01() throws CloneNotSupportedException {ConcretePrototype c1 = new ConcretePrototype();ConcretePrototype c2 = c1.clone();//输出falseSystem.out.println("对象c1和c2是同一个对象？" + (c1==c2));
}

4) 深克隆代码实现

/*** 具体原型类* 实现Cloneable标识接口,表示当前类对象可复制**/
public class ConcretePrototype implements Cloneable, Serializable {private Person person;public Person getPerson() {return person;}public void setPerson(Person person) {this.person = person;}public void show(){System.out.println("嫌疑人姓名: " + person.getName());}public ConcretePrototype() {System.out.println("具体原型对象创建成功!");}@Overrideprotected ConcretePrototype clone() throws CloneNotSupportedException {System.out.println("克隆对象复制成功!");return (ConcretePrototype) super.clone();}
}

import java.io.Serializable;public class Person implements Serializable {private String name;public Person() {}public Person(String name) {this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

//浅拷贝@Testpublic void test02() throws CloneNotSupportedException {ConcretePrototype c1 = new ConcretePrototype();Person p1 = new Person("峰哥");c1.setPerson(p1);//复制c1ConcretePrototype c2 = c1.clone();Person p2 = c2.getPerson();p2.setName("凡哥");c1.show();c2.show();//输出true，克隆对象和原型对象还是共享name属性的System.out.println("对象p1和对象p2是同一个对象吗?" + (p1 == p2));}

如果有需求场景中不允许共享同一对象,那么就需要使用深拷贝,如果想要进行深拷贝需要使用到对象序列化流 (对象序列化之后,再进行反序列化获取到的是不同对象).

4 原型模式应用实例

代码实现

广告模板代码

/*** 广告模板**/
public class AdvTemplate {//广告信名称private String advSubject = "xx银行本月还款达标,可抽iPhone 13等好礼!";//广告信内容private String advContext = "达标用户请在2022年3月1日到2022年3月30日参与抽奖......";public String getAdvSubject() {return advSubject;}public void setAdvSubject(String advSubject) {this.advSubject = advSubject;}public String getAdvContext() {return advContext;}public void setAdvContext(String advContext) {this.advContext = advContext;}
}

邮件类代码

/*** 邮件类**/
public class Mail {private String receiver; //收件人private String subject; //邮件名称private String appellation; //称呼private String context;  //邮件内容private String tail; //邮件尾部 "xx版权所有"public Mail(AdvTemplate advTemplate) {this.subject = advTemplate.getAdvSubject();this.context = advTemplate.getAdvContext();}public String getReceiver() {return receiver;}public void setReceiver(String receiver) {this.receiver = receiver;}public String getSubject() {return subject;}public void setSubject(String subject) {this.subject = subject;}public String getAppellation() {return appellation;}public void setAppellation(String appellation) {this.appellation = appellation;}public String getContext() {return context;}public void setContext(String context) {this.context = context;}public String getTail() {return tail;}public void setTail(String tail) {this.tail = tail;}
}

客户类

/*** 业务场景**/
public class Client {//发送邮件的数量private static int MAX_COUNT = 6;//发送邮件public static void sendMail(Mail mail){System.out.println("标题: " + mail.getSubject() + "\t 收件人: " + mail.getReceiver()+ "\t ...发送成功!");}public static void main(String[] args) {int i = 0;//定义模板Mail mail = new Mail(new AdvTemplate());mail.setTail("xxx银行版权所有");while(i < MAX_COUNT){//每封邮件不同的信息mail.setAppellation(" 先生 (女士)");Random random = new Random();int num = random.nextInt(999999999);mail.setReceiver(num + "@"+"mashibing.com");//发送邮件sendMail(mail);i++;}}}

代码重构
Mail类

public class Mail implements Cloneable {private String receiver; //收件人private String subject; //邮件名称private String appellation; //称呼private String context;  //邮件内容private String tail; //邮件尾部 "xx版权所有"public Mail(AdvTemplate advTemplate) {this.subject = advTemplate.getAdvSubject();this.context = advTemplate.getAdvContext();}public String getReceiver() {return receiver;}public void setReceiver(String receiver) {this.receiver = receiver;}public String getSubject() {return subject;}public void setSubject(String subject) {this.subject = subject;}public String getAppellation() {return appellation;}public void setAppellation(String appellation) {this.appellation = appellation;}public String getContext() {return context;}public void setContext(String context) {this.context = context;}public String getTail() {return tail;}public void setTail(String tail) {this.tail = tail;}@Overrideprotected Mail clone() {Mail mail = null;try {return  (Mail)super.clone();} catch (CloneNotSupportedException e) {e.printStackTrace();return null;}}
}

Client类

public class Client {//发送邮件的数量private static int MAX_COUNT = 6;//发送邮件public static void sendMail(Mail mail){System.out.println("标题: " + mail.getSubject() + "\t 收件人: " + mail.getReceiver()+ "\t ...发送成功!");}public static void main(String[] args) {int i = 0;//定义模板Mail mail = new Mail(new AdvTemplate());mail.setTail("xxx银行版权所有");while(i < MAX_COUNT){//每封邮件不同的信息Mail cloneMail = mail.clone();cloneMail.setAppellation(" 先生 (女士)");Random random = new Random();int num = random.nextInt(999999999);cloneMail.setReceiver(num + "@"+"mashibing.com");//发送邮件sendMail(cloneMail);i++;}}
}

5 原型模式总结

原型模式的优点:



原型模式缺点:
需要为每一个类配备一个克隆方法,而且该克隆方法位于一个类的内部,当对已有的类进行改造时需要修改源代码,违背了开闭原则.

使用场景