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Java设计模式四: 原型模式(Prototype Pattern)

Posted on 2012-12-02 00:27  IT职涯  阅读(22865)  评论(0编辑  收藏  举报

原型模式是一种创建型设计模式,它通过复制一个已经存在的实例来返回新的实例,而不是新建实例.被复制的实例就是我们所称的原型,这个原型是可定制的.
原型模式多用于创建复杂的或者耗时的实例, 因为这种情况下,复制一个已经存在的实例可以使程序运行更高效,或者创建值相等,只是命名不一样的同类数据.

原型模式中的拷贝分为"浅拷贝"和"深拷贝":
浅拷贝: 对值类型的成员变量进行值的复制,对引用类型的成员变量只复制引用,不复制引用的对象.
深拷贝: 对值类型的成员变量进行值的复制,对引用类型的成员变量也进行引用对象的复制.

类图:

实例一:浅拷贝
public class Prototype implements Cloneable {
 private String name;

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

 public Object clone() {
  try {
   return super.clone();
  } catch (CloneNotSupportedException e) {   
   e.printStackTrace();
   return null;
  }
 } 
 
}

public class TestMain {

 public static void main(String[] args) {
  testPrototype();
 }
 
 private static void testPrototype(){
  Prototype pro = new Prototype();
  pro.setName("original object");
  Prototype pro1 = (Prototype)pro.clone();
  pro.setName("changed object1");
  
  System.out.println("original object:" + pro.getName());
  System.out.println("cloned object:" + pro1.getName());
  
 }

}
结果:
original object:changed object1
cloned object:original object


实例二: 浅拷贝
public class Prototype{
 private String name;

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 } 
 
}
public class NewPrototype implements Cloneable {
 
 private String id;
 
 public String getId() {
  return id;
 }

 public void setId(String id) {
  this.id = id;
 }

 private Prototype prototype;
 
 public Prototype getPrototype() {
  return prototype;
 }

 public void setPrototype(Prototype prototype) {
  this.prototype = prototype;
 }


 public Object clone(){ 
  try {
   return super.clone();
  } catch (CloneNotSupportedException e) {
   e.printStackTrace();
   return null;
  }  
 }

}
public class TestMain {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  testPrototype();
 }
 
 private static void testPrototype(){
  Prototype pro = new Prototype();
  pro.setName("original object");
  NewPrototype newObj = new NewPrototype();
  newObj.setId("test1");
  newObj.setPrototype(pro);
  
  NewPrototype copyObj = (NewPrototype)newObj.clone();
  copyObj.setId("testCopy");
  copyObj.getPrototype().setName("changed object");
  
  System.out.println("original object id:" + newObj.getId());
  System.out.println("original object name:" + newObj.getPrototype().getName());
  
  System.out.println("cloned object id:" + copyObj.getId());
  System.out.println("cloned object name:" + copyObj.getPrototype().getName());
  
 }

}

结果:
original object id:test1
original object name:changed object
cloned object id:testCopy
cloned object name:changed object


实例三: 深拷贝
public class Prototype implements Cloneable {
 private String name;

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

 public Object clone() {
  try { 
   return super.clone();
  } catch (CloneNotSupportedException e) {   
   e.printStackTrace();
   return null;
  }
 } 
 
}

public class NewPrototype implements Cloneable {
 
 private String id;
 
 public String getId() {
  return id;
 }

 public void setId(String id) {
  this.id = id;
 }

 private Prototype prototype;
 
 public Prototype getPrototype() {
  return prototype;
 }

 public void setPrototype(Prototype prototype) {
  this.prototype = prototype;
 }


 public Object clone(){
  NewPrototype ret = null;
  try {
   ret = (NewPrototype)super.clone();
   ret.prototype = (Prototype)this.prototype.clone();
   return ret;
  } catch (CloneNotSupportedException e) {
   e.printStackTrace();
   return null;
  }  
 }

}

public class TestMain {

 /**
  * @param args
  */
 public static void main(String[] args) {
  testDeepCopy();
 }
 
 private static void testDeepCopy(){
  Prototype pro = new Prototype();
  pro.setName("original object");
  NewPrototype newObj = new NewPrototype();
  newObj.setId("test1");
  newObj.setPrototype(pro);
  
  NewPrototype copyObj = (NewPrototype)newObj.clone();
  copyObj.setId("testCopy");
  copyObj.getPrototype().setName("changed object");
  
  System.out.println("original object id:" + newObj.getId());
  System.out.println("original object name:" + newObj.getPrototype().getName());
  
  System.out.println("cloned object id:" + copyObj.getId());
  System.out.println("cloned object name:" + copyObj.getPrototype().getName());
  
 }

}

结果:
original object id:test1
original object name:original object
cloned object id:testCopy
cloned object name:changed object

实例四: 利用串行化来做深复制
把对象写道流里的过程是串行化(Serilization)过程;把对象从流中读出来是并行化(Deserialization)过程. 写在流里的是对象的一个拷贝,然后再从流里读出来重建对象.
public class PrototypeSe implements Serializable {

 private String name;

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

}

public class NewPrototypeSe implements Serializable {
 
 private String id;
 
 public String getId() {
  return id;
 }

 public void setId(String id) {
  this.id = id;
 }

 private PrototypeSe prototype;
 
 public PrototypeSe getPrototype() {
  return prototype;
 }

 public void setPrototype(PrototypeSe prototype) {
  this.prototype = prototype;
 }
 
 public Object deepClone(){
  try {
   ByteArrayOutputStream bo = new ByteArrayOutputStream();
   ObjectOutputStream oo = new ObjectOutputStream(bo);   
   oo.writeObject(this);   
   
   ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());
   ObjectInputStream oi = new ObjectInputStream(bi);
   return oi.readObject(); 
  } catch (IOException | ClassNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
   return null;
  }
 }

}

public class TestDeepClone {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  PrototypeSe po = new PrototypeSe();
  po.setName("test1");
  NewPrototypeSe se = new NewPrototypeSe();
  se.setPrototype(po);
  
  NewPrototypeSe deepClone = (NewPrototypeSe)se.deepClone();
  deepClone.getPrototype().setName("test2");
  
  System.out.println("original name:" + se.getPrototype().getName());
  System.out.println("cloned name:" + deepClone.getPrototype().getName());

 }
}
结果:
original name:test1
cloned name:test2