关于spring:深度分析java设计模式中的原型模式看完就没有说不懂的

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：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：孙大圣插入猴毛，变出其余孙大圣

原型模式类图实例

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）

Sheep 类实现 Cloneable 接口重写 clone 办法

 public class Sheep implements Cloneable{

    private String name;
    private int age;
    private 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;}

    @Override
    public String toString() {
        return "Sheep{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", color='" + color + '\'' +
                '}';
    }

    // 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 (Exception e) {System.out.println(e.getMessage());
        }
        return sheep;
    }
}

Client 类测试创立多个 Sheep 的实例，查看是否状态统一。

public class Client {public static void main(String[] args) {System.out.println("原型模式实现对象的创立");
        Sheep sheep=new Sheep("tom",1,"红色");
        Sheep sheep2=(Sheep)sheep.clone();
        Sheep sheep3=(Sheep)sheep.clone();
        Sheep sheep4=(Sheep)sheep.clone();
        System.out.println("sheep2:"+sheep2);
        System.out.println("sheep3:"+sheep3);
        System.out.println("sheep4:"+sheep4);

    }
}

Spring 中原型 Bean 的创立，就是原型模型的利用
代码剖析
ProtoType 类的测试用例

public class ProtoType {public static void main(String[] args) {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
        Object bean = applicationContext.getBean("id01");
        System.out.println("bean" + bean);

        Object bean2 = applicationContext.getBean("id01");

        System.out.println(bean==bean2);

    }
}

beans.xml 配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- 这里咱们的 scope="prototype" 即 原型模式 -->
    <bean id="id01" class="com.spring.bean.Monster" scope="prototype"></bean>
</beans>

追踪 applicationContext.getBean(“id01”)：进入 AbstractApplicationContext 类的 getBean 办法

//---------------------------------------------------------------------
    // Implementation of BeanFactory interface
    //---------------------------------------------------------------------

    @Override
    public Object getBean(String name) throws BeansException {assertBeanFactoryActive();
        return getBeanFactory().getBean(name);
    }

追踪 getBeanFactory(): 进入 AbstractRefreshableApplicationContext 类的 getBeanFactory（）办法

@Override
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");
        }
        return this.beanFactory;
    }
}

追踪 getBean(): 进入 AbstractBeanFactory 类的 getBean()办法

@Override
    public Object getBean(String name) throws BeansException {return doGetBean(name, null, null, false);
    }

追踪 doGetBean(): 进入 doGetBean()办法
通过 if (mbd.isSingleton()) 和 else if (mbd.isPrototype())判断 scope 的作用域,
通过 createBean()创立一个原型模型，返回一个 bean。

/**
     * Return an instance, which may be shared or independent, of the specified bean.
     * @param name the name of the bean to retrieve
     * @param requiredType the required type of the bean to retrieve
     * @param args arguments to use when creating a bean instance using explicit arguments
     * (only applied when creating a new instance as opposed to retrieving an existing one)
     * @param typeCheckOnly whether the instance is obtained for a type check,
     * not for actual use
     * @return an instance of the bean
     * @throws BeansException if the bean could not be created
     */
    @SuppressWarnings("unchecked")
    protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
            @Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {final String beanName = transformedBeanName(name);
        Object bean;

        // Eagerly check singleton cache for manually registered singletons.
        Object sharedInstance = getSingleton(beanName);
        if (sharedInstance != null && args == null) {if (logger.isTraceEnabled()) {if (isSingletonCurrentlyInCreation(beanName)) {
                    logger.trace("Returning eagerly cached instance of singleton bean'" + beanName +
                            "'that is not fully initialized yet - a consequence of a circular reference");
                }
                else {logger.trace("Returning cached instance of singleton bean'" + beanName + "'");
                }
            }
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        }

        else {
            // Fail if we're already creating this bean instance:
            // We're assumably within a circular reference.
            if (isPrototypeCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName);
            }

            // Check if bean definition exists in this factory.
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // Not found -> check parent.
                String nameToLookup = originalBeanName(name);
                if (parentBeanFactory instanceof AbstractBeanFactory) {return ((AbstractBeanFactory) parentBeanFactory).doGetBean(nameToLookup, requiredType, args, typeCheckOnly);
                }
                else if (args != null) {
                    // Delegation to parent with explicit args.
                    return (T) parentBeanFactory.getBean(nameToLookup, args);
                }
                else if (requiredType != null) {
                    // No args -> delegate to standard getBean method.
                    return parentBeanFactory.getBean(nameToLookup, requiredType);
                }
                else {return (T) parentBeanFactory.getBean(nameToLookup);
                }
            }

            if (!typeCheckOnly) {markBeanAsCreated(beanName);
            }

            try {final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                checkMergedBeanDefinition(mbd, beanName, args);

                // Guarantee initialization of beans that the current bean depends on.
                String[] dependsOn = mbd.getDependsOn();
                if (dependsOn != null) {for (String dep : dependsOn) {if (isDependent(beanName, dep)) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "Circular depends-on relationship between'" + beanName + "'and'" + dep + "'");
                        }
                        registerDependentBean(dep, beanName);
                        try {getBean(dep);
                        }
                        catch (NoSuchBeanDefinitionException ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "'"+ beanName +"' depends on missing bean '"+ dep +"'", ex);
                        }
                    }
                }

                // Create bean instance.
                if (mbd.isSingleton()) {sharedInstance = getSingleton(beanName, () -> {
                        try {return createBean(beanName, mbd, args);
                        }
                        catch (BeansException ex) {
                            // Explicitly remove instance from singleton cache: It might have been put there
                            // eagerly by the creation process, to allow for circular reference resolution.
                            // Also remove any beans that received a temporary reference to the bean.
                            destroySingleton(beanName);
                            throw ex;
                        }
                    });
                    bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
                }

                else if (mbd.isPrototype()) {
                    // It's a prototype -> create a new instance.
                    Object prototypeInstance = null;
                    try {beforePrototypeCreation(beanName);
                        prototypeInstance = createBean(beanName, mbd, args);
                    }
                    finally {afterPrototypeCreation(beanName);
                    }
                    bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
                }

                else {String scopeName = mbd.getScope();
                    final Scope scope = this.scopes.get(scopeName);
                    if (scope == null) {throw new IllegalStateException("No Scope registered for scope name'" + scopeName + "'");
                    }
                    try {Object scopedInstance = scope.get(beanName, () -> {beforePrototypeCreation(beanName);
                            try {return createBean(beanName, mbd, args);
                            }
                            finally {afterPrototypeCreation(beanName);
                            }
                        });
                        bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
                    }
                    catch (IllegalStateException ex) {
                        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",
                                ex);
                    }
                }
            }
            catch (BeansException ex) {cleanupAfterBeanCreationFailure(beanName);
                throw ex;
            }
        }

        // Check if required type matches the type of the actual bean instance.
        if (requiredType != null && !requiredType.isInstance(bean)) {
            try {T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
                if (convertedBean == null) {throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
                }
                return convertedBean;
            }
            catch (TypeMismatchException ex) {if (logger.isTraceEnabled()) {
                    logger.trace("Failed to convert bean'" + name + "'to required type'" +
                            ClassUtils.getQualifiedName(requiredType) + "'", ex);
                }
                throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
            }
        }
        return (T) bean;
    }

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，某个类型的对象等，那么浅拷贝会进行援用传递，也就是只是该成员变量的援用值（内存地址）复制一份给新的对象，因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。
克隆羊的案例就是浅拷贝
浅拷贝是应用默认的 clone（）办法来实现 sheep=（Sheep）super。clone（）；

在原有的 Sheep 类根底上增加 public Sheep friend;

public class Sheep implements Cloneable{

    private String name;
    private int age;
    private String color;
    private String address="蒙古羊";
    public Sheep friend;

    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;}

    @Override
    public String toString() {
        return "Sheep{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", color='" + color + '\'' +
                '}';
    }

    // 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 (Exception e) {System.out.println(e.getMessage());
        }
        return sheep;
    }
}

编写 Client 的测试用例，打印 sheep.friend 的 hashCode 值，察看它是否产生了新的对象。

public class Client {public static void main(String[] args) {System.out.println("原型模式实现对象的创立");
        Sheep sheep = new Sheep("tom", 1, "红色");
        sheep.friend=new Sheep("jack",2,"彩色");
        Sheep sheep2 = (Sheep) sheep.clone();
        Sheep sheep3 = (Sheep) sheep.clone();
        Sheep sheep4 = (Sheep) sheep.clone();
        System.out.println("sheep2:" + sheep2+"sheep.friend2="+sheep2.friend.hashCode());
        System.out.println("sheep3:" + sheep3+"sheep.friend3="+sheep3.friend.hashCode());
        System.out.println("sheep4:" + sheep4+"sheep.friend4="+sheep4.friend.hashCode());
    }
}

复制对象的所有根本数据类型的成员变量值
为所有的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，晓得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进行拷贝
深拷贝实现形式一：重写 clone 办法来实现深拷贝
深拷贝实现形式二：通过对象序列化来实现深拷贝

DeepCloneableTarget 类

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，因而咱们这里应用默认的 clone 实现即可.
    @Override
    protected Object clone() throws CloneNotSupportedException {return super.clone();
    }
}

DeepProtoType 类

public class DeepProtoType implements Serializable, Cloneable {

    public String name;
    public DeepCloneableTarget deepCloneableTarget;

    public DeepProtoType() {super();
    }

    // 深拷贝 - 形式 1 应用 clone 办法

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object deep = null;
        // 实现对根本数据类型（属性）和 String 的克隆
        deep = super.clone();
        // 对援用类型的属性，进行独自的解决。DeepProtoType deepProtoType = (DeepProtoType) deep;
        deepProtoType.deepCloneableTarget = (DeepCloneableTarget) deepCloneableTarget.clone();

        return deep;
    }
}

测试用例：Client

public class Client {public static void main(String[] args) throws  Exception{DeepProtoType p = new DeepProtoType();
        p.name="宋江";
        p.deepCloneableTarget=new DeepCloneableTarget("大牛","小牛的");

        // 形式 1 实现深拷贝

        DeepProtoType p2=(DeepProtoType)p.clone();
        System.out.println("p.name="+p.name+"p.deepCloneableTarget="+p.deepCloneableTarget.hashCode());
        System.out.println("p2.name="+p2.name+"p.deepCloneableTarget="+p2.deepCloneableTarget.hashCode());

    }
}

DeepCloneableTarget 类

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，因而咱们这里应用默认的 clone 实现即可.
    @Override
    protected Object clone() throws CloneNotSupportedException {return super.clone();
    }
}

DeepProtoType 类

public class DeepProtoType implements Serializable, Cloneable {

    public String name;
    public DeepCloneableTarget deepCloneableTarget;

    public DeepProtoType() {super();
    }

    // 深拷贝 -  形式 2 通过对象序列化实现（举荐应用）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) {e.printStackTrace();
            return null;
        } finally {
            try {bos.close();
                oos.close();
                bis.close();
                ois.close();} catch (Exception e2) {e2.printStackTrace();
            }
        }
    }
}

Client 测试用例

public class Client {public static void main(String[] args) throws Exception {DeepProtoType p = new DeepProtoType();
        p.name = "宋江";
        p.deepCloneableTarget = new DeepCloneableTarget("大牛", "小牛的");

        // 形式 2 实现深拷贝
        DeepProtoType p3=(DeepProtoType) p.deepClone();

        System.out.println("p.name=" + p.name + "p.deepCloneableTarget=" + p.deepCloneableTarget.hashCode());
        System.out.println("p3.name=" + p3.name + "p.deepCloneableTarget=" + p3.deepCloneableTarget.hashCode());

    }
}

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
如果院士对象发生变化（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。

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关于spring:深度分析java设计模式中的原型模式看完就没有说不懂的

前言

原型模式类图实例

原型模式 java 代码实例

原型模式在 Spirng 框架中源码剖析

浅拷贝

浅拷贝代码实例：

根本介绍

深拷贝代码实例：

形式一：重写 clone 办法

形式二：通过对象序列化来实现深拷贝（举荐应用）

原型模式的注意事项和细节

最初