原型模式-克隆一个对象

在开发一个界面的时候，里面有多个Button，这些对象的属性内容相似。如果一个个实例化Button对象，并设置其属性，那么代码量将会增多。

通过一个原型对象克隆出多个一模一样的对象，该模式被称为原型模式。

图原型模式

Prototype: 抽象原型类，是声名克隆方法的接口，也可以是具体原型类的公共父类。

ConcretePrototype：具体原型类，实现了克隆方法，在克隆方法中返回自己的一个克隆对象。

Client：客户类，让一个原型对象克隆自身从而创建一个新的对象。

public interface ButtonClone {ButtonClone cloneBtn();}public class Button implements ButtonClone{private Double width;private Double height;public Double getWidth() {return width;}public void setWidth(Double width) {this.width = width;}public Double getHeight() {return height;}public void setHeight(Double height) {this.height = height;}@Overridepublic ButtonClone cloneBtn() {Button newBtn = new Button();newBtn.setHeight(this.height);newBtn.setWidth(this.width);return newBtn;}
}

1 浅克隆与深克隆

浅克隆，如果源对象的成员变量是值类型，将复制一份给克隆对象，如果源对象的成员变量是引用类型，则将引用对象的地址复制一份给对象。

深克隆，无论源对象的成员变量是值类型还是引用类型，都将复制一份给目标对象。

1.1 浅克隆

Java的Object类提供了一个clone()方法，可以将一个Java对象浅克隆。能实现克隆Java类必须实现一个标识接口Cloneable，表示这个类支持被复制。

public class ConcretePrototype implements Cloneable{private String name;private String type;private List<String> list = new ArrayList<>();public ConcretePrototype(String name, String type) {this.name = name;this.type = type;}@Overridepublic String toString() {return "ConcretePrototype{" +"name='" + name + '\'' +", type='" + type + '\'' +", list=" + list +'}';}public static void main(String[] args) throws CloneNotSupportedException {ConcretePrototype prototype = new ConcretePrototype("实际类型", "浅克隆");System.out.println("prototype:" + prototype);Object clone = prototype.clone();System.out.println("clone:" + clone);prototype.list.add("hello");System.out.println("clone:" + clone);}}

1.2 深克隆

深克隆，除了对象本身被复制外，对象所包含的所有成员变量也将被复制。在Java中，如果需要实现深克隆，可以通过序列化等方式来实现。需要实例化的对象其类必须实现Serializable接口，否则无法实现序列化操作。

public class CusForm implements Serializable , Cloneable{private String name;private CusFile cusFile;public CusForm(String name, CusFile cusFile) {this.name = name;this.cusFile = cusFile;}public static void main(String[] args) throws IOException, ClassNotFoundException, CloneNotSupportedException {CusForm cusForm = new CusForm("表单", new CusFile());System.out.println(cusForm);System.out.println(cusForm.clone()); //java浅克隆，对象成员变量直接复制地址CusForm deepCloneObj = cusForm.deepClone();System.out.println(deepCloneObj);//        运行结果
//        CusForm{name='表单', cusFile=com.huangmingfu.prototype.deep.CusForm$CusFile@1b6d3586}
//        CusForm{name='表单', cusFile=com.huangmingfu.prototype.deep.CusForm$CusFile@1ddc4ec2}
//        CusForm{name='表单', cusFile=com.huangmingfu.prototype.deep.CusForm$CusFile@1b6d3586}}public CusForm deepClone() throws IOException, ClassNotFoundException {ByteArrayOutputStream outputStream = new ByteArrayOutputStream();ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);objectOutputStream.writeObject(this);ByteArrayInputStream inputStream = new ByteArrayInputStream(outputStream.toByteArray());ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);return (CusForm) objectInputStream.readObject();}@Overridepublic String toString() {return "CusForm{" +"name='" + name + '\'' +", cusFile=" + cusFile +'}';}private static class CusFile implements Serializable{}
}

2 原型管理器

将多个原型对象存储在一个集合中供客户端使用，它是一个专门复制克隆对象的工厂。其中定义了一个集合用于存储原型对象。

图原型管理器

public class DeepClone implements Serializable {public DeepClone deepClone()  {try {ByteArrayOutputStream outputStream = new ByteArrayOutputStream();ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);objectOutputStream.writeObject(this);ByteArrayInputStream inputStream = new ByteArrayInputStream(outputStream.toByteArray());ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);return (DeepClone)objectInputStream.readObject();} catch (Exception e) {System.out.println(e.getMessage());}return null;}
}public class ConcreteA extends DeepClone{private final String name = "concreteA";@Overridepublic String toString() {return "ConcreteA{" +"name='" + name + '\'' +'}' + super.toString();}}public class ConcreteB extends DeepClone{private final String name = "ConcreteB";@Overridepublic String toString() {return "ConcreteB{" +"name='" + name + '\'' +'}' + super.toString();}
}public class PrototypeManager {private final Map<Class<? extends DeepClone>,DeepClone> prototypeMap = new HashMap<>();private final Set<Class<? extends DeepClone>> classes = new HashSet<>();private PrototypeManager() {}private static class HolderClass {private final static PrototypeManager instance = new PrototypeManager();}public static PrototypeManager getInstance() {return HolderClass.instance;}public void addPrototype(DeepClone deepClone) {if (classes.add(deepClone.getClass())) {prototypeMap.put(deepClone.getClass(),deepClone);}}public DeepClone getClone(Class<? extends DeepClone> cls) {DeepClone deepClone = prototypeMap.get(cls);if (deepClone == null) {throw new RuntimeException("克隆体不存在");}return deepClone.deepClone();}}public class Client {public static void main(String[] args) {ConcreteA concreteA = new ConcreteA();ConcreteB concreteB = new ConcreteB();PrototypeManager prototypeManager = PrototypeManager.getInstance();System.out.println(concreteA);System.out.println(concreteB);prototypeManager.addPrototype(concreteA);prototypeManager.addPrototype(concreteB);System.out.println("克隆分割线---------------");DeepClone deepCloneA = prototypeManager.getClone(ConcreteA.class);DeepClone deepCloneB = prototypeManager.getClone(ConcreteB.class);System.out.println(deepCloneA);System.out.println(deepCloneB);//        运行结果
//        ConcreteA{name='concreteA'}com.huangmingfu.prototype.manager.ConcreteA@1b6d3586
//        ConcreteB{name='ConcreteB'}com.huangmingfu.prototype.manager.ConcreteB@4554617c
//        克隆分割线---------------
//        ConcreteA{name='concreteA'}com.huangmingfu.prototype.manager.ConcreteA@30dae81
//        ConcreteB{name='ConcreteB'}com.huangmingfu.prototype.manager.ConcreteB@1b2c6ec2}}