设计模式系列：原型模式

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概念

原型模式是特殊的创建模式，它创建对象不通过直接new的方式产生，而是通过已有的对象复制。

实现

浅拷贝

  • 类图：

图片

Product

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public class Product implements Serializable {

    private String name;

    private String value;

    private ProductB productB;

    public ProductB getProductB() {
        return productB;
    }

    public void setProductB(ProductB productB) {
        this.productB = productB;
    }

    public String getName() {
        return name;
    }

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

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public void display() {
        System.out.println("product name:" + this.name);
        System.out.println("product value:" + this.value);
        System.out.println("productB name:" + this.productB.getName());
    }

    public Product deepClone(){
        try {
            ByteArrayOutputStream bo = new ByteArrayOutputStream();
            ObjectOutputStream oo = new ObjectOutputStream(bo);
            oo.writeObject(this);
            ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());
            ObjectInputStream oi = new ObjectInputStream(bi);
            return (Product)oi.readObject();
        } catch (IOException | ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }
    }

}

ProductB

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public class ProductB implements Serializable {

    private String name;

    public String getName() {
        return name;
    }

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

Client

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public class Client {

    public static void main(String[] args) {
        Product product = new Product();
        ProductB productB = new ProductB();
        productB.setName("B");
        product.setName("X");
        product.setValue("XX");
        product.setProductB(productB);
        Product clone = product.deepClone();
        clone.getProductB().setName("newXX");
        product.display();
        clone.display();
    }

}

执行结果：
Connected to the target VM, address: ‘127.0.0.1:58904’, transport: ‘socket’
product name:X
product value:XX
productB name:B
product name:X
product value:XX
productB name:newXX
Disconnected from the target VM, address: ‘127.0.0.1:58904’, transport: ‘socket’

深拷贝

  • 类图：

图片

Product 

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public class Product implements Cloneable {

    private String name;

    private String value;

    private ProductB productB;

    public ProductB getProductB() {
        return productB;
    }

    public void setProductB(ProductB productB) {
        this.productB = productB;
    }

    public String getName() {
        return name;
    }

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

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public void display() {
        System.out.println("product name:" + this.name);
        System.out.println("product value:" + this.value);
        System.out.println("productB name:" + this.productB.getName());
    }

    public Product clone() {
        try {
            return (Product)super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return null;
    }
}

ProductB

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public class ProductB {

    private String name;

    public String getName() {
        return name;
    }

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

Client

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public class Client {

    public static void main(String[] args) {
        Product product = new Product();
        ProductB productB = new ProductB();
        productB.setName("B");
        product.setName("X");
        product.setValue("XX");
        product.setProductB(productB);
        Product clone = product.clone();
        clone.getProductB().setName("newXX");
        product.display();
        clone.display();
    }

}

执行结果：
Connected to the target VM, address: ‘127.0.0.1:58962’, transport: ‘socket’
product name:X
product value:XX
productB name:newXX
product name:X
product value:XX
productB name:newXX
Disconnected from the target VM, address: ‘127.0.0.1:58962’, transport: ‘socket’

场景

总结

浅拷贝 拷贝后的对象如果有嵌套的复杂对象，那么改变嵌套对象会跟着改变。只拷贝表层的对象信息。
深拷贝，是所有的都拷贝，包括嵌套对象。这里的实现是通过序列化的方式实现。