目录
- 定义
- 解决的问题
- 核心要点
- 类图
- 浅复制与深复制的区别
- 代码实现
- 未使用设计模式
- 实现Cloneable接口
- 深复制-重写clone
- 深复制-通过对象序列化实现(推荐)
- 拓展
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); } }
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