转载 http://blog.csdn.net/u011179993/article/details/51672734
参考:http://www.cnblogs.com/charlesblc/p/6124224.html?utm_source=itdadao&utm_medium=referral
一、实例
class MyBeanPostProcessor implements BeanPostProcessor { @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { System.out.println("=======BeanPostProcessor的postProcessBeforeInitialization========="); return bean; } @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { System.out.println("=======BeanPostProcessor的postProcessAfterInitialization========="); return bean; }} public class Tester implements InitializingBean, DisposableBean, BeanNameAware { private String p; public Tester() { System.out.println("---构造方法---"); System.out.println("p===" + p); } public void setP(String p) { this.p = p; } @Override public void setBeanName(String name) { System.out.println("p===" + p); System.out.println("---BeanNameAware接口setBeanName---"); } @Override public void afterPropertiesSet() throws Exception { System.out.println("---InitializingBean接口afterPropertiesSet---"); } public void initMethod() { System.out.println("---指定的InitMethod---"); } @Override public void destroy() throws Exception { System.out.println("---DisposableBean的destroy方法---"); } public void destroyMethod() { System.out.println("--指定的Destroy方法---"); } @Override public String toString() { return "toString+++"+p; } public static void main(String[] args) throws Exception { DefaultListableBeanFactory factory = new DefaultListableBeanFactory(); factory.addBeanPostProcessor(new MyBeanPostProcessor()); RootBeanDefinition definition = new RootBeanDefinition(Tester.class); definition.setInitMethodName("initMethod"); definition.setDestroyMethodName("destroyMethod"); Map<String, Object> map = new HashMap<>(); map.put("p", "jack"); definition.setPropertyValues(new MutablePropertyValues(map)); factory.registerBeanDefinition("tester", definition); factory.getBean("tester"); factory.destroySingleton("tester"); }}
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去掉多余日志,输出如下:
---构造方法---p===nullp===jack---BeanNameAware接口setBeanName---=======BeanPostProcessor的postProcessBeforeInitialization=========---InitializingBean接口afterPropertiesSet------指定的InitMethod---=======BeanPostProcessor的postProcessAfterInitialization=========---DisposableBean的destroy方法-----指定的Destroy方法---
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我们可以得到实例化bean的大致过程~
1:调用Bean的默认构造方法(当然也可以是指定的其它构造方法),生成bean实例。
2:检查BeanDefinition中是否注入了Bean的属性值,如果有注入,则在bean实例的基础上对其属性进行注入。
3 : 调用Aware相关接口的方法
4 :postProcessBeforeInitialization
5:检查Bean是否实现了InitializingBean接口,如果实现了此接口,则调用afterPropertiesSet()方法。
6:检查Bean配置文件中是否指定了initMethodName属性,如果已指定,则调用此属性对应方法。
7 : postProcessAfterInitialization
销毁过程
1:检查Bean是否实现了DisposableBean 接口,如果实现了此接口,则调用destroy()方法。
2:检查Bean配置文件中是否指定了destroyMethodName属性,如果已指定,则调用此属性对应方法
二、AbstractBeanFactory#doGetBean(..)源码
无论以何种方式获取Bean,都会调用AbstractBeanFactory#doGetBean(..)方法。
去除了这个方法的非重点代码, 保留了部分重要的代码,如下:
protected <T> T doGetBean( String name, Class<T> requiredType, Object[] args, boolean typeCheckOnly) { final String beanName = transformedBeanName(name); Object bean; Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null) { bean = getObjectForBeanInstance(sharedInstance, name, beanName, null); } else { BeanFactory parentBeanFactory = getParentBeanFactory(); if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { String nameToLookup = originalBeanName(name); if (args != null) { return (T) parentBeanFactory.getBean(nameToLookup, args); } else { return parentBeanFactory.getBean(nameToLookup, requiredType); } } final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); checkMergedBeanDefinition(mbd, beanName, args); String[] dependsOn = mbd.getDependsOn(); if (dependsOn != null) { for (String dependsOnBean : dependsOn) { registerDependentBean(dependsOnBean, beanName); getBean(dependsOnBean); } } if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() { @Override public Object getObject() throws BeansException { return createBean(beanName, mbd, args); } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } else if (mbd.isPrototype()) { } } if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) { return getTypeConverter().convertIfNecessary(bean, requiredType); } return (T) bean; }
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1.查找手动注册的Bean实例 或者已经创建过的Bean实例
获取DefaultSingletonBeanRegistry中保存的Bean
2.
代码中 //***之间就是创建Bean的主要代码。下面将针对这部分进行讲解。
三 ,创建Bean重点代码
//********************重点*******************// 创建单实例Beanif (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() { @Override public Object getObject() throws BeansException { return createBean(beanName, mbd, args); //1 } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);}//***************************************
1中进入匿名类ObjectFactory的createBean部分,他实际调用AbstractAutowireCapableBeanFactory#createBean(..)方法
AbstractAutowireCapableBeanFactory#createBean(..)方法
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) { RootBeanDefinition mbdToUse = mbd; Class<?> resolvedClass = resolveBeanClass(mbd, beanName); if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) { mbdToUse = new RootBeanDefinition(mbd); mbdToUse.setBeanClass(resolvedClass); } mbdToUse.prepareMethodOverrides(); Object bean = resolveBeforeInstantiation(beanName, mbdToUse); if (bean != null) { return bean; } Object beanInstance = doCreateBean(beanName, mbdToUse, args); return beanInstance;}
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AbstractAutowireCapableBeanFactory#doCreateBean(..)
重点代码如下:
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) { BeanWrapper instanceWrapper = null; if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } if (instanceWrapper == null) { instanceWrapper = createBeanInstance(beanName, mbd, args); } final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null); Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null); synchronized (mbd.postProcessingLock) { if (!mbd.postProcessed) { applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); mbd.postProcessed = true; } } Object exposedObject = bean; populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) { exposedObject = initializeBean(beanName, exposedObject, mbd); } registerDisposableBeanIfNecessary(beanName, bean, mbd); return exposedObject;}
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调用的是AbstractAutowireCapableBeanFactory#initializeBean(..)方法
这个方法代码简化如下
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) { invokeAwareMethods(beanName, bean); Object wrappedBean = bean; wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); invokeInitMethods(beanName, wrappedBean, mbd); wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName); return wrappedBean;}
一个非常重要的部分就是建立 Bean 对象实例之间的关系,这也是 Spring 框架的核心竞争力,何时、如何建立他们之间的关系请看下面的时序图:
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