原型模式(Prototype Pattern)
是指原型实例指定创建对象的种类,并且通过拷贝这些原型创建新的对象;调用者不需要知道任何创建的细节,不调用构造函数;属于创建型模式;
适用场景:
类初始化消耗资源较多;new 产生的一个对象需要非常繁琐的过程(数据准备、访问权限等);构造函数比较复杂;
循环体中生成大量的对象;
代码示例:
BeanUtils.copy();
JSON.parseObject();
Guava copy工具类
浅克隆
需要创建新对象,但是克隆对象中的属性与原对象指向的是同一地址空间,一个对象中的属性值改变会引起其他克隆对象的值的改变;
public interface Prototype {
Prototype clone();
}
@Data
public class ConcretePrototypeA implements Prototype {
private String name;
private List<String> type;
@Override
public Prototype clone() {
ConcretePrototypeA concretePrototypeA = new ConcretePrototypeA();
concretePrototypeA.setName(this.name);
concretePrototypeA.setType(this.type);
return concretePrototypeA;
}
}
public class SimplePrototypeTest {
public static void main(String[] args) {
ConcretePrototypeA concretePrototypeA = new ConcretePrototypeA();
List<String> list = new ArrayList<>();
list.add("typeAdd_A");
concretePrototypeA.setType(list);
concretePrototypeA.setName("testA");
ConcretePrototypeA copy = (ConcretePrototypeA)concretePrototypeA.clone();
System.out.println("原对象:"+concretePrototypeA.getType());
System.out.println("克隆对象:"+copy.getType());
boolean flag = concretePrototypeA.getType()==copy.getType();
System.out.println("原对象与克隆属性指向的地址是否相等:"+flag);
}
}
测试结果:
原对象:[typeAdd_A]
克隆对象:[typeAdd_A]
原对象与克隆属性指向的地址是否相等:true
深克隆
与单例模式相反,需要重新创建对象,并且将原对象的值赋给新创建的克隆对象,对象属性指向不同的地址空间。
实现方式:
1、可以使用JDK内置的Cloneable方法,需要重写clone()方法;
public interface IDeepPrototype {
IDeepPrototype clone();
}
@Data
public class DeepPrototypeImpl implements IDeepPrototype, Cloneable, Serializable {
private String name;
private List<String> type;
@Override
public IDeepPrototype clone() {
return this.cloneDeep();
}
private IDeepPrototype cloneDeep() {
DeepPrototypeImpl ob = null;
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
System.out.println(this);
try {
ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
objectOutputStream.writeObject(this);
objectOutputStream.flush();
objectOutputStream.close();
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(outputStream.toByteArray());
ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
ob = (DeepPrototypeImpl)objectInputStream.readObject();
System.out.println(ob);
} catch (Exception e) {
e.printStackTrace();
}
return ob;
}
}
public class DeepPrototypeTest {
public static void main(String[] args) {
DeepPrototypeImpl deepPrototype = new DeepPrototypeImpl();
deepPrototype.setName("test1");
List<String> list = new ArrayList<>();
list.add("listAdd1");
deepPrototype.setType(list);
System.out.println("原对象:" + deepPrototype.getType());
try {
DeepPrototypeImpl deepPrototype1 = (DeepPrototypeImpl)deepPrototype.clone();
System.out.println("克隆对象:" + deepPrototype1.getType());
boolean flag = deepPrototype.getType() == deepPrototype1.getType();
System.out.println("原对象与克隆对象属性是否指向同一地址:" + flag);
} catch (Exception e) {
e.printStackTrace();
}
}
}
测试结果:
原对象:[listAdd1]
DeepPrototypeImpl(name=test1, type=[listAdd1])
DeepPrototypeImpl(name=test1, type=[listAdd1])
克隆对象:[listAdd1]
原对象与克隆对象属性是否指向同一地址:false