原型模式在Spring框架应用

• 创建1个spring项目

package com.atguigu.spring.bean;
 
public class Monster {
 
	private Integer id = 10 ;
	
	private String nickname = "牛魔王";
	
	private String skill = "芭蕉扇";
	
	public Monster() {
		System.out.println("monster 创建..");
	}
	
	public Monster(Integer id, String nickname, String skill) {
		//System.out.println("Integer id, String nickname, String skill被调用");
		this.id = id;
		this.nickname = nickname;
		this.skill = skill;
	}
	
	public Monster( String nickname, String skill,Integer id) {
		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;
	}
	
	@Override
	public String toString() {
		return "Monster [id=" + id + ", nickname=" + nickname + ", skill="
				+ skill + "]";
	}
	
}

• 编写beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<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:util="http://www.springframework.org/schema/util"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
 
 <!-- 这里我们的 scope="prototype" 即 原型模式来创建 -->
 <bean id="id01" class="com.atguigu.spring.bean.Monster" 
 	scope="prototype"/>
 
</beans>

• 测试

package com.atguigu.spring.test;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
 
public class ProtoType {
 
	public static void main(String[] args) {
		ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
		// 获取monster[通过id获取monster]
		Object bean = applicationContext.getBean("id01");
		System.out.println("bean" + bean); // 输出 "牛魔王" .....
		
		Object bean2 = applicationContext.getBean("id01");
		System.out.println("bean2" + bean2); //输出 "牛魔王" .....
 
		System.out.println(bean == bean2); // false
		// ConfigurableApplicationContext
	}
 
}

• 查看getBean方法

Object getBean(String name) throws BeansException;

• 查看实现

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

• 查看getBeanFactory方法

@Override
public abstract ConfigurableListableBeanFactory getBeanFactory() throws IllegalStateException;

• 查看实现

	@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;
		}
	}

• 查看getBean方法

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

• 查看实现

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

• 查看doGetBean方法

protected <T> T doGetBean(
			final String name, final Class<T> requiredType, 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.isDebugEnabled()) {
				if (isSingletonCurrentlyInCreation(beanName)) {
					logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
							"' that is not fully initialized yet - a consequence of a circular reference");
				}
				else {
					logger.debug("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 (args != null) {
					// Delegation to parent with explicit args.
					return (T) parentBeanFactory.getBean(nameToLookup, args);
				}
				else {
					// No args -> delegate to standard getBean method.
					return parentBeanFactory.getBean(nameToLookup, requiredType);
				}
			}
 
			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 dependsOnBean : dependsOn) {
						if (isDependent(beanName, dependsOnBean)) {
							throw new BeanCreationException("Circular depends-on relationship between '" +
									beanName + "' and '" + dependsOnBean + "'");
						}
						registerDependentBean(dependsOnBean, beanName);
						getBean(dependsOnBean);
					}
				}
 
				// Create bean instance.
				if (mbd.isSingleton()) {        // 是否是单例
					sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
						@Override
						public Object getObject() throws BeansException {
							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()) {    // 是否是原型
					// 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 '" + scopeName + "'");
					}
					try {
						Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
							@Override
							public Object getObject() throws BeansException {
								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;
			}
		}