妙的设计例如Bean工厂设计、Bean的生命周期、tx、aop、web、mvc等最核心基本的Bean设计是Spring

的框架的灵魂本文就Bean的生命周期全流程做源码程度上的解析欢迎各位大佬指点江山。

先上一张DefaultListableBeanFactory的UML图来来感受Spring

框架设计的强大跟着DefaultListableBeanFactory去揭开Spring框架的核心面纱。

DefaultListableBeanFactory掌管了Bean生命周期的大权Bean的创建、初始化、销毁添加BeanPostProcessor等功能可以说是Spring框架最全的Bean工厂,

创建并注册BeanDefinition

我们可以使用DefaultListableBeanFactory

对象注册一个BeanDefition,

createBeanByDefaultListableBeanFactory(final

Class?

DefaultListableBeanFactory();RootBeanDefinition

beanDefinition

RootBeanDefinition(beanClass);beanDefinition.setInitMethodName(testMethod);beanDefinition.setDestroyMethodName(testDestroy);beanFactory.registerBeanDefinition(testBean,

beanDefinition);//添加BeanPostProcessorbeanFactory.addBeanPostProcessor(new

BeanPostProcessor()

postProcessBeforeInitialization(Object

bean,

{//System.out.println(执行前..);return

bean;}Overridepublic

postProcessAfterInitialization(Object

bean,

{System.out.println(执行后..);return

bean;}});return

testMethod(){System.out.println(初始化..);}public

void

testDestroy(){System.out.println(销毁..);}}Testpublic

void

testDefaultListableBeanFactory()

{final

User.class;DefaultListableBeanFactory

beanFactory

createBeanByDefaultListableBeanFactory(beanClass);User

user

User.class);System.out.println(user

user);}打印结果:

postProcessBeforeIntialization()

init-method()postProcessAfterInitialization()

为了进一步理解Bean的生命周期下面我们继续看Aware、BeanPostProcessor、InitialzingBean接口的执行顺序。

BeanNameAware、BeanFactoryAware、BeanClassLoaderAware

BeanNameAware、BeanFactoryAware、BeanClassLoaderAware接口分别是在初始化Bean之前调用的我们可以利用BeanName、BeanFactory、ClassLoader去开发一些业务。

/***

执行BeanNameAware、BeanClassLoaderAware、BeanFactoryAware的接口。

*

param

bean).setBeanName(beanName);}if

(bean

bean).setBeanClassLoader(bcl);}}if

(bean

bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);}}}

BeanPostProcessor

BeanPostProcessor接口里有2个默认方法分别为PostProcessBeforeInitialization和PostProcessAfterInitialization。

public

org.springframework.beans.BeansException

case

org.springframework.beans.factory.InitializingBean#afterPropertiesSet*/Nullabledefault

Object

postProcessBeforeInitialization(Object

bean,

InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation}

method,*

org.springframework.beans.BeansException

case

org.springframework.beans.factory.InitializingBean#afterPropertiesSet*

see

org.springframework.beans.factory.FactoryBean*/Nullabledefault

Object

postProcessAfterInitialization(Object

bean,

当所有的Bean属性被BeanFactory设置完后允许你用afterPropertieSet()方法做一次调。

/***

org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName*

see

org.springframework.context.ApplicationContextAware*/

public

该接口一般可以用来做属性实例的校验比如当前Bean依赖了哪些Bean,

如果依赖的Bean没有初始化就应该抛出异常例如DataSourceTransactionManager里用该方法去校验DataSource有没有被初始化。

public

AbstractPlatformTransactionManagerimplements

InitializingBean

{setNestedTransactionAllowed(true);}/***

Create

DataSourceTransactionManager(DataSource

dataSource)

{this();setDataSource(dataSource);afterPropertiesSet();}Overridepublic

void

IllegalArgumentException(Property

dataSource

required);}}}InitializingBean接口的afterPropertiesSet()在AbstractAutowireCapableBeanFactoryinvokeInitMethods方法里被调用。

protected

执行InitializingBean的afterPropertiesSet()if

(isInitializingBean

!mbd.isExternallyManagedInitMethod(afterPropertiesSet)))

{if

{AccessController.doPrivileged((PrivilegedExceptionActionObject)

{((InitializingBean)

bean).afterPropertiesSet();return

null;},

getAccessControlContext());}catch

pae)

执行InitialingBean的afterProperties()接口。

((InitializingBean)

bean).afterPropertiesSet();}}if

(mbd

(StringUtils.hasLength(initMethodName)

!(isInitializingBean

afterPropertiesSet.equals(initMethodName))

!mbd.isExternallyManagedInitMethod(initMethodName))

{invokeCustomInitMethod(beanName,

bean,

三、DefaultListableBeanFactory的父类AbstractAutowireCapableBeanFactory

AbstarctAutowireCapableBeanFactory

是一个抽象类实现了AutowireCapableBeanFactory和AbstarctBeanFactory接口initializeBean方法实现了实例化Bean的整个流程。

protected

{AccessController.doPrivileged((PrivilegedActionObject)

bean);return

getAccessControlContext());}else

{//

执行所有的BeanNameAware、BeanClassLoaderAware、BeanFactoryAware接口把对象塞入到参数里交给开发者使用。

invokeAwareMethods(beanName,

bean);}//

执行所有的BeanPostProcessor里的postProcessBeforeInitialization()Object

wrappedBean

applyBeanPostProcessorsBeforeInitialization(wrappedBean,

beanName);}try

其中包含InitializingBean接口里的AfterPropertiesSet()方法和自定义的init()方法invokeInitMethods(beanName,

wrappedBean,

执行所有的BeanPostProcessor的postProcessAfterInitialization()方法if

(mbd

applyBeanPostProcessorsAfterInitialization(wrappedBean,

beanName);}return