Java原型模式
小小张自由—>张有博 人气:0定义
用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。
原型模式其实就是从一个对象在创建另外一个可定制的对象，不需要知道任何创建的细节
解决的问题
在运行期建立和删除原型。
经常用于：
类初始化消耗资源较多
构造函数比较复杂
核心要点
1.实现cloneable 接口，重写Object的clone方法
2.利用已有的一个原型对象，快速地生成和原型对象一样的实例。
类图
浅复制与深复制的区别
浅复制：基本数据类型进行值传递、引用数据类型的指针仍是指向原来的对象（成员变量）。
深复制：基本数据类型进行值传递、引用数据类型开辟新的内存空间。
代码实现
需求：实现克隆羊
有一头羊，需要经过赋值再克隆出两头。
未使用设计模式
/**
* 克隆羊类
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 14:51
*/
public class Sheep {
private String name;
private Integer age;
private String color;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public Sheep() {
}
public Sheep(String name, Integer age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
}Main方法
/**
*
* 传统模式
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 14:47
*/
public class Client {
public static void main(String[] args) {
//小羊
Sheep sheep=new Sheep("小红",8,"红色");
//克隆羊
Sheep sheep2=sheep;
Sheep sheep3=sheep;
System.out.println("通过赋值，指针还是指向sheep");
System.out.println(sheep);
System.out.println(sheep2);
System.out.println(sheep3);
}
}
//通过赋值，指针还是指向sheep
//com.promsing.creational.prototype.type1.Sheep@1b6d3586
//com.promsing.creational.prototype.type1.Sheep@1b6d3586
//com.promsing.creational.prototype.type1.Sheep@1b6d3586
实现Cloneable接口
Cloneable是标记型的接口，它们内部都没有方法和属性，实现 Cloneable来表示该对象能被克隆，能使用Object.clone()方法。
如果没有实现 Cloneable的类对象调用clone()就会抛出CloneNotSupportedException。
实现Cloneable默认是浅复制
/**
* 克隆羊
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 14:53
*/
public class Sheep implements Cloneable {
private String name;
private Integer age;
private String color;
/**
* 羊的朋友
*/
private Sheep friend;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public Sheep() {
}
public Sheep getFriend() {
return friend;
}
public void setFriend(Sheep friend) {
this.friend = friend;
}
public Sheep(String name, Integer age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
/**
* 克隆该实例，调用object.clone的方法
* @return
*/
@Override
protected Sheep clone() {
Sheep sheep = null;
try {
sheep = (Sheep) super.clone();
} catch (CloneNotSupportedException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
return sheep;
}
}
Main方法
/**
* 浅复制：浅复制：基本数据类型进行值传递、引用数据类型的指针仍是指向原来的对象（成员变量）。
*/
public class ShallowClient {
public static void main(String[] args) {
Sheep sheep=new Sheep("小红",9,"红色");
sheep.setFriend(new Sheep("小黑",10,"黑色"));
Sheep sheep1 = sheep.clone();//开辟了新的空间
Sheep sheep2 = sheep.clone();
//浅复制
System.out.println("原型羊"+sheep);
System.out.println("克隆羊"+sheep1+"-朋友羊-"+sheep1.getFriend());
System.out.println("克隆羊"+sheep2+"-朋友羊-"+sheep2.getFriend());
//原型羊com.promsing.creational.prototype.type3.Sheep@1b6d3586
//克隆羊com.promsing.creational.prototype.type3.Sheep@4554617c-朋友羊-com.promsing.creational.prototype.type3.Sheep@74a14482
//克隆羊com.promsing.creational.prototype.type3.Sheep@1540e19d-朋友羊-com.promsing.creational.prototype.type3.Sheep@74a14482
}
}
一定要实现接口cloneable 否则报错：
Exception in thread "main" java.lang.CloneNotSupportedException: com.promsing.creational.prototype.type4.Sheep
at java.lang.Object.clone(Native Method)
at com.promsing.creational.prototype.type4.Sheep.clone(Sheep.java:76)
at com.promsing.creational.prototype.type4.DeepClient.main(DeepClient.java:14)
深复制-重写clone
羊类、房子类都需要实现Cloneable接口
房子类
/**
* 房子类
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 15:27
*/
public class House implements Cloneable {
//地址
private String address;
//尺寸
private Integer size;
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Integer getSize() {
return size;
}
public void setSize(Integer size) {
this.size = size;
}
/**
* 克隆的方法
* @return
* @throws CloneNotSupportedException
*/
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}羊类
/**
* 克隆羊-深拷贝
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 15:26
*/
public class Sheep implements Cloneable {
private String name;
private Integer age;
private String color;
/**
* 羊的房子:引用类型
*/
private House house;
public House getHouse() {
return house;
}
public void setHouse(House house) {
this.house = house;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public Sheep() {
}
public Sheep(String name, Integer age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
/**
* 克隆该实例，调用object，clone的方法
*
* @return
* @throws CloneNotSupportedException
*/
@Override
protected Object clone() throws CloneNotSupportedException {
//对基本数据类型进行处理
Sheep deep = null;
deep = (Sheep) super.clone();
//对引用类型进行处理
//进行再次克隆
House clone = (House) deep.getHouse().clone();
deep.setHouse(clone);
return deep;
}
}Main
/**
* 深复制:羊类、房子类都需要重写clone的接口，比较麻烦。不符合开闭
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 15:38
*/
public class DeepClient {
public static void main(String[] args) throws CloneNotSupportedException {
Sheep sheep=new Sheep("黑",90,"heisee");
sheep.setHouse(new House());
Sheep clone = (Sheep)sheep.clone();
System.out.println("原本的对象");
System.out.println(sheep);
System.out.println(sheep.getHouse());
System.out.println("克隆的对象");
System.out.println(clone);
System.out.println(clone.getHouse());
//开辟了新的内存空间
//原本的对象
//com.promsing.creational.prototype.type4.Sheep@1b6d3586
//com.promsing.creational.prototype.type4.House@4554617c
//克隆的对象
//com.promsing.creational.prototype.type4.Sheep@74a14482
//com.promsing.creational.prototype.type4.House@1540e19d
}
}
深复制-通过对象序列化实现（推荐）
羊类、房子类都需要实现Serializable接口。注意这里可以不实现Cloneable了。
房子类
/**
* 房子类
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 15:27
*/
public class House implements Serializable{
//地址
private String address;
//尺寸
private Integer size;
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Integer getSize() {
return size;
}
public void setSize(Integer size) {
this.size = size;
}
}
羊类
/**
* 克隆羊-深拷贝
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 15:26
*/
public class Sheep implements Serializable {
private String name;
private Integer age;
private String color;
/**
* 羊的房子:引用类型
*/
private House house;
public House getHouse() {
return house;
}
public void setHouse(House house) {
this.house = house;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public Sheep() {
}
public Sheep(String name, Integer age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
/**
* 序列化的方式：进行深复制
* 写着麻烦：用着简单。支持开闭原则
* @return
*/
public Object deepClone() {
//创建流对象
ByteArrayOutputStream bos = null;
ObjectOutputStream oos = null;
ByteArrayInputStream bis = null;
ObjectInputStream ois = null;
try {
//序列化
bos = new ByteArrayOutputStream();
oos = new ObjectOutputStream(bos);
oos.writeObject(this); //当前这个对象以对象流的方式输出
//反序列化
bis = new ByteArrayInputStream(bos.toByteArray());
ois = new ObjectInputStream(bis);
Sheep copyObj = (Sheep) ois.readObject();
return copyObj;
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
return null;
} finally {
//关闭流
try {
bos.close();
oos.close();
bis.close();
ois.close();
} catch (Exception e2) {
// TODO: handle exception
System.out.println(e2.getMessage());
}
}
}
}
Main
/**
* 深复制
*
* @author Promsing(张有博)
* @version 1.0.0
* @since 2022/9/3 - 15:38
*/
public class DeepClient {
public static void main(String[] args) throws CloneNotSupportedException {
Sheep sheep=new Sheep("黑",90,"heisee");
sheep.setHouse(new House());
Sheep clone = (Sheep)sheep.deepClone();
System.out.println("原本的对象");
System.out.println(sheep);
System.out.println(sheep.getHouse());
System.out.println("克隆的对象");
System.out.println(clone);
System.out.println(clone.getHouse());
}
}
拓展
Spring使用原型模式：@scope(“prototype”)
public static void main(String[] args) throws IOException {
//new一个容器
AnnotationConfigWebApplicationContext context =
new AnnotationConfigWebApplicationContext();
System.out.println("run success");
OrderService bean = context.getBean(OrderService.class);
}
//根据getBean点进去
public <T> T getBean(Class<T> requiredType) throws BeansException {
assertBeanFactoryActive();
return getBeanFactory().getBean(requiredType);
}
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
后续走到了。AbstractBeanFactory类中的doGetBean方法中里边代码做判断mbd.isPrototype()
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
//代码省略~~~~
}
else {
//代码省略~~~~
try {
//代码省略~~~~
// Create bean instance.
//判断是否是单例
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
//判断是否是多例（原型）
//这里会创建一个新的对象
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
//代码省略~~~~
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
//代码省略~~~~
}
return (T) bean;
}
ArrayList实现了Cloneable接口
public Object clone() {
try {
ArrayList<?> v = (ArrayList<?>) super.clone();
v.elementData = Arrays.copyOf(elementData, size);
v.modCount = 0;
return v;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError(e);
}
}加载全部内容