构造型模式之Prototype（原型）模式

1.如果你期望根据给定的例子创建一个对象，可使用Prototype（原型）模式

2.区分Shallow Clone&Deep Clone

Shallow Clone: 对基本类型的成员变量进行值的复制,对引用类型的成员变量只复制引用,不复制引用的对象.

Deep Clone: 对基本类型的成员变量进行值的复制,对引用类型的成员变量也进行引用对象的复制.

参考：http://blog.csdn.net/shootyou/article/details/3945221

3.举例

//第一个原型类：clone()方法包括了Shallow Clone与Deep Clone的实现
public class FirstPrototype implements Cloneable{
private String name;
private SecondPrototype secondPrototype;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public SecondPrototype getSecondPrototype() {
return secondPrototype;
}
public void setSecondPrototype(SecondPrototype secondPrototype) {
this.secondPrototype = secondPrototype;
}
@Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
//Shallow Clone
//return super.clone();
//Deep Clone
FirstPrototype clone = (FirstPrototype) super.clone();
clone.setSecondPrototype((SecondPrototype) secondPrototype.clone());
return clone;
}

}

//第二个原型类：该类没有引用类型的成员变量
public class SecondPrototype implements Cloneable{
private int age;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
return super.clone();
}
}

//测试类
public class Test {
public static void main(String[] args){
SecondPrototype sp0 = new SecondPrototype();
sp0.setAge(0);
FirstPrototype fp0 = new FirstPrototype();
fp0.setName("fp0");
fp0.setSecondPrototype(sp0);

System.out.println(fp0.getName());
System.out.println(fp0.getSecondPrototype().getAge());

try {
FirstPrototype fp1 = (FirstPrototype) fp0.clone();
fp1.setName("fp1");
fp1.getSecondPrototype().setAge(1);
System.out.println("clone: " + fp1.getName());
System.out.println("clone: " + fp1.getSecondPrototype().getAge());
} catch (CloneNotSupportedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

System.out.println(fp0.getName());
System.out.println(fp0.getSecondPrototype().getAge());

}
}

//Shallow Clone结果
fp0
0
clone: fp1
clone: 1
fp0
1
//Deep Clone结果
fp0
0
clone: fp1
clone: 1
fp0
0

4.总结：Prototype（原型）模式不通过实例化类来创建一个新的未初始化的实例，而是通过复制一个现有对象来生成新的对象。该模式要注意Shallow Clone与Deep Clone的区别，否则会造成原来实例化对象数据被修改而造成逻辑错误。