java学习笔记之原型模式及深浅拷贝 (2)

第一种方式：重写clone()方法实现深克隆，参考下面代码实现：

public class Sheep implements Cloneable { private String sname; private Date birthday; public Mother mother; public Sheep() { } public Sheep(String sname, Date birthday,Mother mother ) { this.sname = sname; this.birthday = birthday; this.mother=mother; } @Override public String toString() { return "Sheep{" + "sname='" + sname + '\'' + ", birthday=" + birthday + ", mother=" + mother + '}'; } @Override protected Object clone() throws CloneNotSupportedException { Sheep sheep=null; try { Object obj= super.clone(); sheep=(Sheep) obj; sheep.mother=(Mother) mother.clone(); } catch (Exception e) { e.printStackTrace(); } return sheep; } }

多利的妈咪

public class Mother implements Cloneable { private int age; private String name; public Mother(int age, String name) { this.age = age; this.name = name; } @Override protected Object clone() throws CloneNotSupportedException { return super.clone(); } }

客户端测试：

public class Client { public static void main(String[] args) throws CloneNotSupportedException { Sheep sheep=new Sheep("多利",new Date(),new Mother(12,"多利的妈妈")); Sheep sheep1=(Sheep) sheep.clone(); System.out.println("sheep:"+sheep); System.out.println("sheep1:"+sheep1); System.out.println("sheephashcode:"+sheep.mother.hashCode()); System.out.println("sheep1hashcode:"+sheep1.mother.hashCode()); } }

运行结果：hashcode 的值不一样

sheep:Sheep{sname='多利', birthday=Sun May 17 13:20:51 CST 2020, mother=com.designpattern.pattern.prototypepattern.sprototype.Mother@7adf9f5f}
sheep1:Sheep{sname='多利', birthday=Sun May 17 13:20:51 CST 2020, mother=com.designpattern.pattern.prototypepattern.sprototype.Mother@85ede7b}
sheephashcode:2061475679
sheep1hashcode:140435067

第二种方式：序列化和反序列化

需要在Sheep ,Mother 类实现一个序列化 Serializable，具体代码和上面第一种方式的代码一样，就是这Sheep代码中增加以下这段核心代码：

// 通过对象的序列化实现 public Object deepClone() throws Exception { ByteArrayOutputStream bos=new ByteArrayOutputStream(); ObjectOutputStream oos=new ObjectOutputStream(bos); oos.writeObject(this); ObjectInputStream ois=new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray())); Sheep sheep=(Sheep) ois.readObject(); return sheep; }

运行结果：

sheep:Sheep{sname='多利', birthday=Sun May 17 13:51:23 CST 2020, mother=com.designpattern.pattern.prototypepattern.sprototype.Mother@72ea2f77}
sheep1:Sheep{sname='多利', birthday=Sun May 17 13:51:23 CST 2020, mother=com.designpattern.pattern.prototypepattern.sprototype.Mother@17f052a3}
sheephashcode:1927950199
sheep1hashcode:401625763

三、原型模式的应用场景

Spring 中bean 的scope 属性的声明：

<bean scope="prototype"/> public class ProtoType { public static void main(String[] args) { // TODO Auto-generated method stub ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); // 获取monster[通过id获取monster] Object bean = applicationContext.getBean("student"); System.out.println("bean:" + bean); Object bean2 = applicationContext.getBean("student"); System.out.println("bean1" + bean2); System.out.println(bean == bean2); } }

运行结果

bean:com.atguigu.spring.bean.Student@52bf72b5
bean1com.atguigu.spring.bean.Student@37afeb11
false

四、小结

优点：

1、创建新的对象比较复杂时，可以利用原型模式创建新的对象，不用重新初始化对象，而是动态地获得对象运行时的状态。

2、如果原始对象发生变化，其克隆的对象也会发生响应的变化，不需要修改代码来实现

缺点：

需要为每一个类配置一个克隆方法，需要器修改源代码，不符合OCP原则。