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原型模式详解

一、原型模式概述

原型模式(Prototype Pattern)是一种创建型设计模式，它通过复制现有对象来创建新对象，而不是通过new关键字实例化。

核心特点

克隆代替新建：通过复制现有对象创建新实例
性能优势：避免昂贵的初始化过程
灵活性：运行时动态改变对象类型
简化创建：隐藏对象创建细节

二、原型模式的实现方式

1. 基本实现（浅拷贝）

// 实现Cloneable接口
public class Sheep implements Cloneable {private String name;private int age;public Sheep(String name, int age) {this.name = name;this.age = age;}// 重写clone方法@Overridepublic Sheep clone() {try {return (Sheep) super.clone();} catch (CloneNotSupportedException e) {throw new AssertionError();}}// getter和setterpublic String getName() {return name;}
}// 使用示例
Sheep original = new Sheep("Dolly", 2);
Sheep cloned = original.clone();

2. 深拷贝实现

public class DeepCloneExample implements Cloneable {private String data;private List<String> items;public DeepCloneExample(String data, List<String> items) {this.data = data;this.items = new ArrayList<>(items);}@Overridepublic DeepCloneExample clone() {try {DeepCloneExample cloned = (DeepCloneExample) super.clone();// 对引用类型进行深拷贝cloned.items = new ArrayList<>(this.items);return cloned;} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}

3. 使用序列化实现深拷贝

import java.io.*;public class DeepCopySerializable implements Serializable {private String name;private Date birthDate;public DeepCopySerializable deepCopy() {try {ByteArrayOutputStream bos = new ByteArrayOutputStream();ObjectOutputStream oos = new ObjectOutputStream(bos);oos.writeObject(this);ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());ObjectInputStream ois = new ObjectInputStream(bis);return (DeepCopySerializable) ois.readObject();} catch (Exception e) {throw new RuntimeException("深拷贝失败", e);}}
}

三、原型模式的应用场景

1. 对象初始化成本高

public class ExpensiveObject implements Cloneable {private String data;private List<String> cachedResults;public ExpensiveObject() {// 模拟耗时初始化this.data = loadDataFromDatabase();this.cachedResults = computeExpensiveResults();}@Overridepublic ExpensiveObject clone() {try {return (ExpensiveObject) super.clone();} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}// 使用示例
ExpensiveObject prototype = new ExpensiveObject();
ExpensiveObject copy = prototype.clone();

2. 游戏开发中的角色克隆

public abstract class GameCharacter implements Cloneable {protected String name;protected int health;protected List<Item> inventory;@Overridepublic GameCharacter clone() {try {GameCharacter clone = (GameCharacter) super.clone();// 深拷贝inventoryclone.inventory = new ArrayList<>(this.inventory);return clone;} catch (CloneNotSupportedException e) {throw new AssertionError();}}public abstract void render();
}

3. 配置对象复制

public class SystemConfig implements Cloneable {private String theme;private int timeout;private Map<String, String> preferences;@Overridepublic SystemConfig clone() {try {SystemConfig clone = (SystemConfig) super.clone();// 深拷贝Mapclone.preferences = new HashMap<>(this.preferences);return clone;} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}

四、原型模式的变体

1. 原型管理器

import java.util.HashMap;
import java.util.Map;public class PrototypeManager {private static Map<String, Cloneable> prototypes = new HashMap<>();static {prototypes.put("default", new DefaultPrototype());prototypes.put("custom", new CustomPrototype());}public static Cloneable getPrototype(String type) {return prototypes.get(type).clone();}
}

2. 结合工厂方法

public abstract class Shape implements Cloneable {public abstract void draw();@Overridepublic Shape clone() {try {return (Shape) super.clone();} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}public class ShapeFactory {private static Map<String, Shape> shapeMap = new HashMap<>();static {shapeMap.put("circle", new Circle());shapeMap.put("square", new Square());}public static Shape getShape(String type) {return shapeMap.get(type).clone();}
}

五、原型模式的注意事项

深拷贝与浅拷贝
- 浅拷贝：基本类型复制值，引用类型复制引用
- 深拷贝：引用类型也创建新对象
Cloneable接口问题
- clone()方法是Object类的protected方法
- 需要重写为public方法
- 考虑使用复制构造函数或工厂方法替代
final字段问题
- 克隆后无法修改final字段的值
- 需要特别注意final引用类型的字段