需求
现在有一只羊tom 姓 名为 : tom, 年龄为:1 颜 色为:白色,请编写程序创建和 tom羊属性完全相同的5只羊 。
传统写法
sheep
public class Sheep { private String name; private int age; private String color; public Sheep(String name, int age, String color) { super(); this.name = name; this.age = age; this.color = color; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } @Override public String toString() { return "Sheep [name=" + name + ", age=" + age + ", color=" + color + "]"; } }
客户端测试Client
public class Client { public static void main(String[] args) { // TODO Auto-generated method stub //传统的方法 Sheep sheep = new Sheep("tom", 1, "白色"); Sheep sheep2 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor()); Sheep sheep3 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor()); Sheep sheep4 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor()); Sheep sheep5 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor()); //.... System.out.println(sheep); System.out.println(sheep2); System.out.println(sheep3); System.out.println(sheep4); System.out.println(sheep5); } }
运行结果:
优缺点:
1)优点是比较好理解,简单易操作。
2)在 创建新的对 象 时 总是需要重新获取原始对象的属性,如果创建的对象比较复杂时,效率较低
3)总是需要重新初始化对象,而不是动态地获得对象运行时的状态 , 不够灵活
4)改进的思路分析
思路
Java 中 Object 类是所有类的根类 Object 类提供了一个 clone() 方法,该方法可以将一 个 Java 对象复制一份 ,但是需要实现 clone Java 类必须要实现一个接口 Cloneable该接口表示该类能够复制且具有复制的能 力即**原型模式**.
原型模式
基本介绍
UML类图
原型模式解决决克隆羊问题
Sheep
public class Sheep implements Cloneable { private String name; private int age; private String color; private String address = "蒙古羊"; public Sheep friend; //是对象, 克隆是会如何处理 public Sheep(String name, int age, String color) { super(); this.name = name; this.age = age; this.color = color; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } @Override public String toString() { return "Sheep [name=" + name + ", age=" + age + ", color=" + color + ", address=" + address + "]"; } //克隆该实例,使用默认的clone方法来完成 @Override protected Object clone() { Sheep sheep = null; try { sheep = (Sheep) super.clone(); } catch (Exception e) { // TODO: handle exception System.out.println(e.getMessage()); } // TODO Auto-generated method stub return sheep; } }
Client
public class Client { public static void main(String[] args) { System.out.println("原型模式完成对象的创建"); // TODO Auto-generated method stub Sheep sheep = new Sheep("tom", 1, "白色"); sheep.friend = new Sheep("jack", 2, "黑色"); Sheep sheep2 = (Sheep)sheep.clone(); //克隆 Sheep sheep3 = (Sheep)sheep.clone(); //克隆 Sheep sheep4 = (Sheep)sheep.clone(); //克隆 Sheep sheep5 = (Sheep)sheep.clone(); //克隆 System.out.println("sheep2 =" + sheep2 + "sheep2.friend=" + sheep2.friend.hashCode()); System.out.println("sheep3 =" + sheep3 + "sheep3.friend=" + sheep3.friend.hashCode()); System.out.println("sheep4 =" + sheep4 + "sheep4.friend=" + sheep4.friend.hashCode()); System.out.println("sheep5 =" + sheep5 + "sheep5.friend=" + sheep5.friend.hashCode()); } }
运行结果:
原型模式在Spring框架中源码分析
如果我们配置的生成bean的方式是 property,追踪代码会看到,在第4步是通过原型模式来生成多个实例。
浅拷贝
这里的friend作为一个引用类型,其地址被每个实例化得到,如果一个实例改了friend,其他的实例也会受到影响,这就是浅拷贝,我们的目标只是想得到其全部属性就行了,而不是得到这个引用对象的地址。我们需要的是深拷贝。
深拷贝
引用对象成员 DeepCloneableTarget
public class DeepCloneableTarget implements Serializable, Cloneable{ private static final long serialVersionUID = 1L; private String cloneName; private String cloneClass; public DeepCloneableTarget(String cloneName, String cloneClass) { this.cloneName = cloneName; this.cloneClass = cloneClass; } //因为该类的属性,都是String , 因此我们这里使用默认的clone完成即可 @Override protected Object clone() throws CloneNotSupportedException { return super.clone(); } @Override public String toString() { return "DeepCloneableTarget{" + "cloneName='" + cloneName + '\'' + ", cloneClass='" + cloneClass + '\'' + '}'; } }
实现拷贝的类 DeepProtoType
public class DeepProtoType implements Serializable, Cloneable { public String name; //String 属性 public DeepCloneableTarget deepCloneableTarget;// 引用类型 public DeepProtoType() { super(); } //深拷贝 - 方式 1 使用clone 方法 @Override protected Object clone() throws CloneNotSupportedException { Object deep = null; //这里完成对基本数据类型(属性)和String的克隆 deep = super.clone(); //对引用类型的属性,进行单独处理 DeepProtoType deepProtoType = (DeepProtoType)deep; deepProtoType.deepCloneableTarget = (DeepCloneableTarget)deepCloneableTarget.clone(); // TODO Auto-generated method stub return deepProtoType; } //深拷贝 - 方式2 通过对象的序列化实现 (推荐) 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); DeepProtoType copyObj = (DeepProtoType)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()); } } } }
重写clone方式
通过对象的序列化实现 (推荐)
测试Client
public class Client { public static void main(String[] args) throws Exception { // TODO Auto-generated method stub DeepProtoType p = new DeepProtoType(); p.name = "宋江"; p.deepCloneableTarget = new DeepCloneableTarget("大牛", "小牛"); //方式1 完成深拷贝 DeepProtoType p1 = (DeepProtoType) p.clone(); System.out.println("p.name=" + p.name + "p.deepCloneableTarget=" + p.deepCloneableTarget.hashCode() +"=="+ p.deepCloneableTarget); System.out.println("p1.name=" + p.name + "p1.deepCloneableTarget=" + p1.deepCloneableTarget.hashCode()+"=="+ p1.deepCloneableTarget); //方式2 完成深拷贝 DeepProtoType p2 = (DeepProtoType) p.deepClone(); System.out.println("p.name=" + p.name + "p.deepCloneableTarget=" + p.deepCloneableTarget.hashCode()+"=="+ p.deepCloneableTarget); System.out.println("p2.name=" + p.name + "p2.deepCloneableTarget=" + p2.deepCloneableTarget.hashCode()+"=="+ p.deepCloneableTarget); } }
测试结果:
可以看到hashcode 不一样,也就是引用地址不是一个,属性也深度克隆了。完美实现!!
原型模式的注意事项和细节
源码地址
https://github.com/hufanglei/java-design/tree/master/src/com/atguigu/prototype
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