前言需要
接下里介绍的是Java 的设计模式之一：原型模式
当初有一只羊 tom
姓名为: tom, 年龄为：1，色彩为：红色
请编写程序创立和 tom 羊 属性完全相同的 10 只羊
请问你会怎么制作呢？
一、什么是原型模式
原型模式(Prototype 模式)是指：用原型实例指定创建对象的品种，并且通过拷贝这些原型，创立新的对象
原型模式是一种创立型设计模式，容许一个对象再创立另外一个可定制的对象，无需晓得如何创立的细节
工作原理是:通过将一个原型对象传给那个要动员创立的对象，这个要动员创立的对象通过申请原型对象拷贝它们本人来施行创立，即对象.clone()
形象的了解：齐天大圣孙悟空插入猴毛， 变出其它孙大圣
原理结构图阐明
Prototype : 原型类，申明一个克隆本人的接口
ConcretePrototype: 具体的原型类, 实现一个克隆本人的操作
Client: 让一个原型对象克隆本人，从而创立一个新的对象(属性一样）
二、通过示例阐明状况
咱们依照传统形式解决之前提出的克隆羊问题
class Sheep{ public String name; public int age; public String color; public Sheep(String name, int age, String color) { 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; }}咱们生成一只羊，而后依据这只羊的属性创立十只羊
public static void main(String[] args) { //传统的办法 Sheep sheep = new Sheep("tom", 1, "红色"); 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()); //......... }传统的形式的优缺点
- 长处是
比拟好了解，简略易操作。 - 在
创立新的对象时，总是须要从新获取原始对象的属性，如果创立的对象比较复杂时，效率较低 - 总是
须要从新初始化对象，而不是动静地取得对象运行时的状态, 不够灵便
改良的思路剖析
思路：Java 中 Object 类是所有类的根类，Object 类提供了一个 clone()办法.
该办法能够将一个 Java 对象复制一份，然而须要实现 clone 的Java 类必须要实现一个接口 Cloneable，该接口示意该类可能复制且具备复制的能力 =>原型模式
class Sheep implements Cloneable { //省略要害代码.... //克隆该实例，应用默认的clone办法来实现 @Override protected Object clone(){ Sheep sheep = null; try { sheep = (Sheep) super.clone(); } catch (CloneNotSupportedException e) { e.printStackTrace(); } return sheep; }}那么咱们是应用demo看看，与传统模式有何变动呢？
public static void main(String[] args) { //传统的办法 Sheep sheep = new Sheep("tom", 1, "红色"); Sheep sheep2 = (Sheep)sheep.clone(); Sheep sheep3 = (Sheep)sheep.clone(); Sheep sheep4 = (Sheep)sheep.clone(); //.........}咱们在应用原型模式的时候，克隆则就不无需每次new一个对象
并且如果Sheep办法，如何增加了一个字段属性，也会本人实现初始化
class Sheep implements Cloneable { private String name; private int age; private String color; private String address; public Sheep(String name, int age, String color, String address) { this.name = name; this.age = age; this.color = color; this.address = address; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; }}public static void main(String[] args) { //传统的办法 Sheep sheep = new Sheep("tom", 1, "红色","内蒙古"); Sheep sheep2 = (Sheep)sheep.clone(); Sheep sheep3 = (Sheep)sheep.clone(); Sheep sheep4 = (Sheep)sheep.clone(); //.........}三、Spring框架源码解析
Spring 中原型 bean 的创立，就是原型模式的利用
咱们应用一个类来举例说明一下
class Monster{ private Integer id = 10; private String nickName = "牛魔王"; private String skill = "芭蕉扇"; public Monster() { System.out.println("monster 创立...."); } public Monster(Integer id, String nickName, String skill) { this.id = id; this.nickName = nickName; this.skill = skill; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getNickName() { return nickName; } public void setNickName(String nickName) { this.nickName = nickName; } public String getSkill() { return skill; } public void setSkill(String skill) { this.skill = skill; }}同时咱们这里还有一个bean的xml文件配置
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:util="http://www.springframework.org/schema/util" xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation=" http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.2.xsd" <!--咱们这里的scope="prototype" 即原型模式来创立--> <bean id="id01" class="com.spring.bean.Monster" scope="prototype"/></beans>接下来咱们应用demo，测试原型模式下的bean，获取对象是否相等
public static void main(String[] args) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml"); Object bean1 =applicationContext.getBean("id01"); System.out.println("bean1 = "+bean1); Object bean2 =applicationContext.getBean("id01"); System.out.println("bean2 = "+bean2); System.out.println(bean1 == bean2);}运行后果如下：monster 创立....bean1=Monster{id=10,nickName='牛魔王', skill='芭蕉扇'}monster 创立....bean2=Monster{id=10,nickName='牛魔王', skill='芭蕉扇'}false阐明这两个对象，他的变量雷同，然而不是同一个对象，返回了false
那么咱们须要晓得他是在哪里用到了原型呢？咱们debug看看
public abstract class AbstractApplicationContext extends DefaultResourceLoader implements ConfigurableApplicationContext, DisposableBean { //省略其余要害代码.... public Object getBean(String name) throws BeansException { return this.getBeanFactory().getBean(name); } public <T> T getBean(String name, Class<T> requiredType) throws BeansException { return this.getBeanFactory().getBean(name, requiredType); } public <T> T getBean(Class<T> requiredType) throws BeansException { return this.getBeanFactory().getBean(requiredType); } public Object getBean(String name, Object... args) throws BeansException { return this.getBeanFactory().getBean(name, args); } public boolean containsBean(String name) { return this.getBeanFactory().containsBean(name); } public boolean isSingleton(String name) throws NoSuchBeanDefinitionException { return this.getBeanFactory().isSingleton(name); } public boolean isPrototype(String name) throws NoSuchBeanDefinitionException { return this.getBeanFactory().isPrototype(name); }}咱们发现他是采纳BeanFactory里的getBean，那么我进到外面去看
public abstract class AbstractRefreshableApplicationContext extends AbstractApplicationContext { //省略其余要害代码.... public final ConfigurableListableBeanFactory getBeanFactory() { synchronized(this.beanFactoryMonitor) { if (this.beanFactory == null) { throw new IllegalStateException("BeanFactory not initialized or already closed - call 'refresh' before accessing beans via the ApplicationContext"); } else { return this.beanFactory; } } }}返回工厂后，咱们就进BeanFactory的getBean办法里看看
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory { //省略其余要害代码.... public AbstractBeanFactory() {} public AbstractBeanFactory(BeanFactory parentBeanFactory) { this.parentBeanFactory = parentBeanFactory; } public Object getBean(String name) throws BeansException { return this.doGetBean(name, (Class)null, (Object[])null, false); } public <T> T getBean(String name, Class<T> requiredType) throws BeansException { return this.doGetBean(name, requiredType, (Object[])null, false); } public Object getBean(String name, Object... args) throws BeansException { return this.doGetBean(name, (Class)null, args, false); } public <T> T getBean(String name, Class<T> requiredType, Object... args) throws BeansException { return this.doGetBean(name, requiredType, args, false); } }发现是调用doGetBean办法，那咱们再进去doGetBean办法看看
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory { //省略其余要害代码.... protected <T> T doGetBean(String name, Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException { final String beanName = this.transformedBeanName(name); Object sharedInstance = this.getSingleton(beanName); Object bean; if (sharedInstance != null && args == null) { if (this.logger.isDebugEnabled()) { if (this.isSingletonCurrentlyInCreation(beanName)) { this.logger.debug("Returning eagerly cached instance of singleton bean '" + beanName + "' that is not fully initialized yet - a consequence of a circular reference"); } else { this.logger.debug("Returning cached instance of singleton bean '" + beanName + "'"); } } bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, (RootBeanDefinition)null); } else { if (this.isPrototypeCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } BeanFactory parentBeanFactory = this.getParentBeanFactory(); if (parentBeanFactory != null && !this.containsBeanDefinition(beanName)) { String nameToLookup = this.originalBeanName(name); if (args != null) { return parentBeanFactory.getBean(nameToLookup, args); } return parentBeanFactory.getBean(nameToLookup, requiredType); } if (!typeCheckOnly) { this.markBeanAsCreated(beanName); } try { final RootBeanDefinition mbd = this.getMergedLocalBeanDefinition(beanName); this.checkMergedBeanDefinition(mbd, beanName, args); String[] dependsOn = mbd.getDependsOn(); String[] arr$; if (dependsOn != null) { arr$ = dependsOn; int len$ = dependsOn.length; for(int i$ = 0; i$ < len$; ++i$) { String dependsOnBean = arr$[i$]; this.getBean(dependsOnBean); this.registerDependentBean(dependsOnBean, beanName); } } if (mbd.isSingleton()) { sharedInstance = this.getSingleton(beanName, new ObjectFactory<Object>() { public Object getObject() throws BeansException { try { return AbstractBeanFactory.this.createBean(beanName, mbd, args); } catch (BeansException var2) { AbstractBeanFactory.this.destroySingleton(beanName); throw var2; } } }); bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } else if (mbd.isPrototype()) { arr$ = null; Object prototypeInstance; try { this.beforePrototypeCreation(beanName); prototypeInstance = this.createBean(beanName, mbd, args); } finally { this.afterPrototypeCreation(beanName); } bean = this.getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); } else { String scopeName = mbd.getScope(); Scope scope = (Scope)this.scopes.get(scopeName); if (scope == null) { throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'"); } try { Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() { public Object getObject() throws BeansException { AbstractBeanFactory.this.beforePrototypeCreation(beanName); Object var1; try { var1 = AbstractBeanFactory.this.createBean(beanName, mbd, args); } finally { AbstractBeanFactory.this.afterPrototypeCreation(beanName); } return var1; } }); bean = this.getObjectForBeanInstance(scopedInstance, name, beanName, mbd); } catch (IllegalStateException var21) { throw new BeanCreationException(beanName, "Scope '" + scopeName + "' is not active for the current thread; " + "consider defining a scoped proxy for this bean if you intend to refer to it from a singleton", var21); } } } catch (BeansException var23) { this.cleanupAfterBeanCreationFailure(beanName); throw var23; } } if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) { try { return this.getTypeConverter().convertIfNecessary(bean, requiredType); } catch (TypeMismatchException var22) { if (this.logger.isDebugEnabled()) { this.logger.debug("Failed to convert bean '" + name + "' to required type [" + ClassUtils.getQualifiedName(requiredType) + "]", var22); } throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); } } else { return bean; } }}代码很多，我这里采纳图片的形式标注进去
对于在spring框架中原型模式，因为小编程度无限，暂且先理解这么多
四、浅拷贝和深拷贝
浅拷贝的介绍
对于数据类型是根本数据类型的成员变量，浅拷贝会间接进行值传递，也就是将该属性值复制一份给新的对象。
对于数据类型是援用数据类型的成员变量，比如说成员变量是某个数组、某个类的对象等，那么浅拷贝会进行援用传递，也就是只是将该成员变量的援用值（内存地址）复制一份给新的对象。
为实际上两个对象的该成员变量都指向同一个实例。
在这种状况下，在一个对象中批改该成员变量会影响到另一个对象的该成员变量值
比如说之前克隆羊，咱们增加一个对象字段
class Sheep implements Cloneable { //省略其余关键性代码..... private Sheep friend; public Sheep(String name, int age, String color, String address, Sheep friend) { this.name = name; this.age = age; this.color = color; this.address = address; this.friend = friend; } public Sheep getFriend() { return friend; } public void setFriend(Sheep friend) { this.friend = friend; }}这时咱们创立demo ，一起看看领会援用拷贝地址指向新对象
public static void main(String[] args) { Sheep friend = new Sheep("jack", 2, "彩色","内蒙古"); Sheep sheep = new Sheep("tom", 1, "红色","内蒙古",friend); Sheep sheep2 = (Sheep)sheep.clone(); Sheep sheep3 = (Sheep)sheep.clone(); Sheep sheep4 = (Sheep)sheep.clone(); System.out.println(sheep2 + "hashCode"+sheep2.friend.hashCode()); System.out.println(sheep3+ "hashCode"+sheep3.friend.hashCode()); System.out.println(sheep4+ "hashCode"+sheep4.friend.hashCode()); } 运行后果如下：Sheep{name='tom', age=1, color='红色', address='内蒙古}hashCode460141958Sheep{name='tom', age=1, color='红色', address='内蒙古}hashCode460141958Sheep{name='tom', age=1, color='红色', address='内蒙古}hashCode460141958有没有发现，咱们输入好敌人的时候，都是指向同一个地址
这证实咱们没有真正的拷贝一个好敌人的对象，咱们称这为浅拷贝
浅拷贝是应用默认的 clone()办法来实现：就是sheep = (Sheep) super.clone();
深拷贝根本介绍
复制对象的所有根本数据类型的成员变量值
为所有援用数据类型的成员变量申请存储空间，并复制每个援用数据类型成员变量所援用的对象，直到该对象可达的所有对象。也就是说，对象进行深拷贝要对整个对象(包含对象的援用类型)进行拷贝
深拷贝实现形式 1：重写 clone 办法来实现深拷贝
深拷贝实现形式 2：通过对象序列化实现深拷贝(举荐)
咱们通过新的示例类来举例说明这两种状况
class DeepCloneableTarget implements Cloneable { public String name; //String 属 性 public String cloneClass; //String 属 性 public DeepCloneableTarget() { super(); } public DeepCloneableTarget(String name, String cloneClass) { this.name = name; this.cloneClass = cloneClass; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getCloneClass() { return cloneClass; } public void setCloneClass(String cloneClass) { this.cloneClass = cloneClass; } @Override protected Object clone() throws CloneNotSupportedException { return super.clone(); }}咱们应用默认的拷贝办法，当初咱们增加多一个类增加对象援用
class DeepProtoType implements Cloneable { public String name; //String 属 性 public DeepCloneableTarget deepCloneableTarget;// 援用类型 public DeepProtoType() {} public DeepProtoType(String name, DeepCloneableTarget deepCloneableTarget) { this.name = name; this.deepCloneableTarget = deepCloneableTarget; } public String getName() { return name; } public void setName(String name) { this.name = name; } public DeepCloneableTarget getDeepCloneableTarget() { return deepCloneableTarget; } public void setDeepCloneableTarget(DeepCloneableTarget deepCloneableTarget) { this.deepCloneableTarget = deepCloneableTarget; }}那么咱们的第一种形式是：采纳重写 clone 办法来实现深拷贝
class DeepProtoType implements Cloneable { //省略其余要害代码.... @Override protected Object clone() throws CloneNotSupportedException { //实现对根本数据类型和String类型的拷贝 Object deep = null; deep = super.clone(); //再实现对类里的援用类型拷贝 DeepProtoType deepProtoType = (DeepProtoType)deep; deepProtoType.setDeepCloneableTarget((DeepCloneableTarget)deepCloneableTarget.clone()); return deepProtoType; }}接下里咱们应用demo 看看第一种形式的深拷贝成果怎么样？
public static void main(String[] args) { DeepCloneableTarget target = new DeepCloneableTarget("大牛", "大牛的类"); DeepProtoType p1 = new DeepProtoType(); p1.setName("小明"); p1.setDeepCloneableTarget(target); try { //形式 1 实现深拷贝 DeepProtoType p2 = (DeepProtoType)p1.clone(); System.out.println("p1.name = " + p1.name + " p1.deepCloneableTarget=" + p1.deepCloneableTarget.hashCode()); System.out.println("p2.name = " + p1.name + " p2.deepCloneableTarget=" + p2.deepCloneableTarget.hashCode()); } catch (CloneNotSupportedException e) { e.printStackTrace(); }}运行后果如下：p1.name = 小明 p1.deepCloneableTarget=460141958p2.name = 小明 p2.deepCloneableTarget=1163157884这种形式采纳先拷贝根本数据类型再拷贝援用类型
1.这种形式如果DeepCloneableTarget里也有援用类型的类，那么它也须要重写这个办法，这就会导致多重重写
2.如果多个类的援用就会导致很繁琐，工作量微小，关系简单
论断：只适宜一层关系的援用，理论不太举荐
那么咱们的第二种形式是：通过对象序列化实现深拷贝(举荐)
应用序列化的形式，咱们须要实现Serializable接口
public class DeepProtoType implements Serializable, Cloneable{ //省略其余要害代码....}public class DeepCloneableTarget implements Serializable, Cloneable{ //省略其余要害代码....}public class DeepProtoType implements Serializable, Cloneable{ //省略其余要害代码.... //深拷贝 - 形式 2 通过对象的序列化实现 (举荐) public Object deepClone() { //创立流对象 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); //以后这个对象以对象流的形式输入 //反序列化 bis = new ByteArrayInputStream(bos.toByteArray()); ois = new ObjectInputStream(bis); DeepProtoType copyObj = (DeepProtoType) ois.readObject(); return copyObj; } catch (Exception e) { return null; } finally { //敞开流 try { bos.close(); oos.close(); bis.close(); ois.close(); } catch (Exception e2) { } } } }接下里咱们应用demo 看看第二种形式的深拷贝成果怎么样？
public static void main(String[] args) { DeepCloneableTarget target = new DeepCloneableTarget("大牛", "小牛"); DeepProtoType p1 = new DeepProtoType(); p1.setName("小明"); p1.setDeepCloneableTarget(target); //形式 2 实现深拷贝 DeepProtoType p2 = (DeepProtoType) p1.deepClone(); System.out.println("p1.name = " + p1.name + " p1.deepCloneableTarget=" + p1.deepCloneableTarget.hashCode()); System.out.println("p2.name = " + p1.name + " p2.deepCloneableTarget=" + p2.deepCloneableTarget.hashCode());}运行后果如下：p1.name = 小明 p1.deepCloneableTarget=1836019240p2.name = 小明 p2.deepCloneableTarget=363771819五、原型模式的注意事项和细节
创立新的对象比较复杂时，能够利用原型模式简化对象的创立过程，同时也可能提高效率
不必从新初始化对象，而是动静地取得对象运行时的状态
如果原始对象发生变化(减少或者缩小属性)，其它克隆对象的也会产生相应的变动，无需批改代码
在实现深克隆的时候可能须要比较复杂的代码
毛病：须要为每一个类装备一个克隆办法，这对全新的类来说不是很难，但对已有的类进行革新时，须要批改其源代码，违反了 ocp 准则，这点请留神.
参考资料
尚硅谷：设计模式（韩顺平老师）：单例模式
Refactoring.Guru：《深刻设计模式》