原型模式

原型模式(Prototype): 用原型实例指定创建对象的种类，并且通过拷贝原型来创建新的实例对象。它允许一个对象再创建另外一个可定制的对象，根本无需知道任何创建细节，工作原理，通过将一个原型对象传给那个要发动创建的对象，这个发动创建对象通过请求原型对象拷贝它们自己来创建。
通俗点，就是通过拷贝来进行创建实例。
原型模式适合在什么场景使用？一是类初始化需要消化非常多的资源，这个资源包括数据、硬件资源
等；二是通过new 产生一个对象需要非常繁琐的数据准备或访问权限，则可以使用原型模式；三是一个对
象需要提供给其他对象访问，而且各个调用者可能都需要修改其值时，可以考虑使用原型模式拷贝多个对
象供调用者使用。在实际项目中，原型模式很少单独出现，一般是和工厂方法模式一起出现，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。

package pattern.prototype;

public class Car implements Cloneable {
	private String name;
	private Wheel wheel;

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

	public String getName() {
		return name;
	}

	public void setWheel(Wheel wheel) {
		this.wheel = wheel;
	}

	public Wheel getWheel() {
		return wheel;
	}

	public Object clone() {
		Car car = null;
		try {
			car = (Car) super.clone();
			car.wheel= (Wheel) this.wheel.clone();
		} catch (CloneNotSupportedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return car;
	}
}

package pattern.prototype;

public class Wheel implements Cloneable {
	private String name;

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

	public String getName() {
		return name;
	}

	public Object clone() {
		Wheel wheel = null;
		try {
			wheel = (Wheel) super.clone();
		} catch (CloneNotSupportedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return wheel;
	}
}

package pattern.prototype;

public class Test {
	public static void main(String[] args) {
		Car car1 = new Car();
		car1.setName("Benz");
		Wheel w = new Wheel();
		w.setName("AA");
		car1.setWheel(w);
		Car car2=(Car) car1.clone();
		System.out.println(car1.getName());
		System.out.println(car1.getWheel().getName());
		System.out.println("*********************************");
		car2.getWheel().setName("BB");
		car2.setName("toyota");
		System.out.println(car2.getName());
		System.out.println(car2.getWheel().getName());
		System.out.println("*********************************");

		System.out.println(car1.getName());
		System.out.println(car1.getWheel().getName());
	}
}

下面是通过Java序列化实现的原型模式,通过将对象序列化,可以实现深拷贝,这种方式可以不用在每个关联对象中添加clone方法,只须实现Serializable接口.故是一种提倡用法:

package pattern.prototype;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class Car implements Serializable {
	/**
	 * 
	 */

	private String name;
	private Wheel wheel;

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

	public String getName() {
		return name;
	}

	public void setWheel(Wheel wheel) {
		this.wheel = wheel;
	}

	public Wheel getWheel() {
		return wheel;
	}

	// public Object clone() {
	// Car car = null;
	// try {
	// car = (Car) super.clone();
	// car.wheel= (Wheel) this.wheel.clone();
	// } catch (CloneNotSupportedException e) {
	// // TODO Auto-generated catch block
	// e.printStackTrace();
	// }
	// return car;
	// }

	public static Object copy(Object oldObj) {
		Object obj = null;
		try {
			System.out.println(oldObj + " dfdf");
			// Write the object out to a byte array
			ByteArrayOutputStream bos = new ByteArrayOutputStream();
			ObjectOutputStream out = new ObjectOutputStream(bos);
			out.writeObject(oldObj);
			out.flush();
			out.close();
			// Retrieve an input stream from the byte array and read
			// a copy of the object back in.
			ByteArrayInputStream bis = new ByteArrayInputStream(bos
					.toByteArray());
			ObjectInputStream in = new ObjectInputStream(bis);
			obj = in.readObject();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException cnfe) {
			cnfe.printStackTrace();
		}
		return obj;
	}

}

package pattern.prototype;

import java.io.Serializable;

public class Wheel implements Serializable {
	private String name;

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

	public String getName() {
		return name;
	}

	public Object clone() {
		Wheel wheel = null;
		try {
			wheel = (Wheel) super.clone();
		} catch (CloneNotSupportedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return wheel;
	}
}

package pattern.prototype;

public class Test {
	public static void main(String[] args) {
		Car car1 = new Car();
		car1.setName("Benz");
		Wheel w = new Wheel();
		w.setName("AA");
		car1.setWheel(w);
		Car car2=(Car) Car.copy(car1);
		System.out.println(car1.getName());
		System.out.println(car1.getWheel().getName());
		System.out.println("*********************************");
		car2.getWheel().setName("BB");
		car2.setName("toyota");
		System.out.println(car2.getName());
		System.out.println(car2.getWheel().getName());
		System.out.println("*********************************");

		System.out.println(car1.getName());
		System.out.println(car1.getWheel().getName());
	}
}