原型模式
作用:为了实现可定制的拷贝,人为的控制拷贝哪些东西
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:
实现:
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