设计模式-创建型-原型模式

• 通过原型对象，复制（拷贝）一个与原型对象相同的新对象。
• 其实就是拷贝对象。可分为 浅拷贝（对象内的对象属性与原型对象地址引用一样） 和 深拷贝（对象内的对象属性是拷贝的新对象）

• 在对象特别复杂时，或者有性能或安全问题时，可以考虑使用原型模式

• Java中Object类的clone()方法实现了浅拷贝
• 实现Cloneable，并重写clone()方法，即可进行浅拷贝

public class Test1 {

    public static void main(String[] args) throws CloneNotSupportedException {
        
        // 浅克隆可以拷贝基本类型
        Duck duck = new Duck();
        duck.setName("duck");
        Duck clone = duck.clone();
        clone.setName("clone");
        System.out.println(duck == clone);
        duck.show();
        clone.show();

        // 浅克隆对引用类型是进行地址拷贝
        BlackDuck blackDuck = new BlackDuck();
        duck.setBlackDuck(blackDuck);
        blackDuck.setName("duck");

        clone.setBlackDuck(blackDuck);
        clone.getBlackDuck().setName("clone");
        duck.say();
        clone.say();
    }
}

// 实现Cloneable接口。（规范，不实现该接口会CloneNotSupportedException）
class Duck implements Cloneable{

    private String name;

    public Duck() {
        System.out.println("clone没有调用构造函数");
    }

    @Override
    //重写Object的clone方法（clone方法是protected需重写）
    protected Duck clone() throws CloneNotSupportedException {
        return (Duck) super.clone();
    }

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

    public void show() {
        System.out.println(name);
    }

    // 浅拷贝地址一样，需深拷贝
    private BlackDuck blackDuck;

    public void say() {
        System.out.println(blackDuck.getName());
    }

    public void setBlackDuck(BlackDuck blackDuck) {
        this.blackDuck = blackDuck;
    }

    public BlackDuck getBlackDuck() {
        return blackDuck;
    }
}

class BlackDuck {
    private String name;

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

    public String getName() {
        return name;
    }
}

• 可以通过序列化，反序列化进行深拷贝

public class Test {
    public static void main(String[] args) throws Exception {

        Duck duck = new Duck();
        BlackDuck blackDuck = new BlackDuck();
        blackDuck.setName("duck");
        duck.setBlackDuck(blackDuck);

        // 深拷贝
        write(duck);
        Duck clone = (Duck) read();
        clone.getBlackDuck().setName("clone");
        duck.say();
        clone.say();
    }

    private static void write(Object o) throws Exception {
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("D:\work\study\design\single.txt"));
        out.writeObject(o);
        out.close();
    }

    private static Object read() throws Exception {
        ObjectInputStream input = new ObjectInputStream(new FileInputStream("D:\work\study\design\single.txt"));
        Object o = input.readObject();
        return o;
    }
}

class Duck implements Serializable {

    private BlackDuck blackDuck;

    public void say() {
        System.out.println(blackDuck.getName());
    }

    public void setBlackDuck(BlackDuck blackDuck) {
        this.blackDuck = blackDuck;
    }

    public BlackDuck getBlackDuck() {
        return blackDuck;
    }
}

class BlackDuck implements Serializable {
    private String name;

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

    public String getName() {
        return name;
    }
}