网站选域名,wordpress标签颜色,快速网站建设公司哪家好,外国网站域名在哪查Spring框架作为Java王国的地基#xff0c;我觉得它包含了很多精妙的设计#xff0c;例如Bean工厂设计、Bean的生命周期、tx、aop、web、mvc等#xff0c;最核心基本的Bean设计是Spring 的框架的灵魂#xff0c;本文就Bean的生命周期全流程做源码程度上的解析#xff0c;欢… Spring框架作为Java王国的地基我觉得它包含了很多精妙的设计例如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。 一、DefaultListableBeanFactory 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, 掌握DefaultListableBeanFactory 是非常有必要的。
1. 创建并注册BeanDefinition 我们可以使用DefaultListableBeanFactory 对象注册一个BeanDefition, 使用registerBeanDefinition()方法 如果想要加入一个BeanPostProcessor, 可以使用addBeanPostProcessor()方法。 private DefaultListableBeanFactory createBeanByDefaultListableBeanFactory(final Class? beanClass) {DefaultListableBeanFactory beanFactory new DefaultListableBeanFactory();RootBeanDefinition beanDefinition new RootBeanDefinition(beanClass);beanDefinition.setInitMethodName(testMethod);beanDefinition.setDestroyMethodName(testDestroy);beanFactory.registerBeanDefinition(testBean, beanDefinition);//添加BeanPostProcessorbeanFactory.addBeanPostProcessor(new BeanPostProcessor() {Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {//System.out.println(执行前..);return bean;}Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {System.out.println(执行后..);return bean;}});return beanFactory;}public static class User {public void testMethod(){System.out.println(初始化..);}public void testDestroy(){System.out.println(销毁..);}}Testpublic void testDefaultListableBeanFactory() {final Class? beanClass User.class;DefaultListableBeanFactory beanFactory createBeanByDefaultListableBeanFactory(beanClass);User user beanFactory.getBean(testBean, User.class);System.out.println(user user);}打印结果: 从打印结果可以知道User这个Bean的三个方法的执行顺序:
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。
二、Bean的生命周期
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 beanName* param bean*/private void invokeAwareMethods(final String beanName, final Object bean) {if (bean instanceof Aware) {if (bean instanceof BeanNameAware) {((BeanNameAware) bean).setBeanName(beanName);}if (bean instanceof BeanClassLoaderAware) {ClassLoader bcl getBeanClassLoader();if (bcl ! null) {((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);}}if (bean instanceof BeanFactoryAware) {((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);}}} BeanPostProcessor BeanPostProcessor接口里有2个默认方法分别为PostProcessBeforeInitialization和PostProcessAfterInitialization。
public interface BeanPostProcessor {/*** Apply this BeanPostProcessor to the given new bean instance ibefore/i any bean* initialization callbacks (like InitializingBeans {code afterPropertiesSet}* or a custom init-method). The bean will already be populated with property values.* The returned bean instance may be a wrapper around the original.* pThe default implementation returns the given {code bean} as-is.* param bean the new bean instance* param beanName the name of the bean* return the bean instance to use, either the original or a wrapped one;* if {code null}, no subsequent BeanPostProcessors will be invoked* throws org.springframework.beans.BeansException in case of errors* see org.springframework.beans.factory.InitializingBean#afterPropertiesSet*/Nullabledefault Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {return bean;}/*** Apply this BeanPostProcessor to the given new bean instance iafter/i any bean* initialization callbacks (like InitializingBeans {code afterPropertiesSet}* or a custom init-method). The bean will already be populated with property values.* The returned bean instance may be a wrapper around the original.* pIn case of a FactoryBean, this callback will be invoked for both the FactoryBean* instance and the objects created by the FactoryBean (as of Spring 2.0). The* post-processor can decide whether to apply to either the FactoryBean or created* objects or both through corresponding {code bean instanceof FactoryBean} checks.* pThis callback will also be invoked after a short-circuiting triggered by a* {link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method,* in contrast to all other BeanPostProcessor callbacks.* pThe default implementation returns the given {code bean} as-is.* param bean the new bean instance* param beanName the name of the bean* return the bean instance to use, either the original or a wrapped one;* if {code null}, no subsequent BeanPostProcessors will be invoked* throws org.springframework.beans.BeansException in case of errors* see org.springframework.beans.factory.InitializingBean#afterPropertiesSet* see org.springframework.beans.factory.FactoryBean*/Nullabledefault Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {return bean;}}InitializingBean InitializingBean接口官方解释: 当所有的Bean属性被BeanFactory设置完后允许你用afterPropertieSet()方法做一次调。
/*** Interface to be implemented by beans that need to react once all their* properties have been set by a BeanFactory: for example, to perform custom* initialization, or merely to check that all mandatory properties have been set.** pAn alternative to implementing InitializingBean is specifying a custom* init-method, for example in an XML bean definition.* For a list of all bean lifecycle methods, see the* {link BeanFactory BeanFactory javadocs}.** author Rod Johnson* see BeanNameAware* see BeanFactoryAware* see BeanFactory* see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName* see org.springframework.context.ApplicationContextAware*/
public interface InitializingBean {/*** Invoked by a BeanFactory after it has set all bean properties supplied* (and satisfied BeanFactoryAware and ApplicationContextAware).* pThis method allows the bean instance to perform initialization only* possible when all bean properties have been set and to throw an* exception in the event of misconfiguration.* throws Exception in the event of misconfiguration (such* as failure to set an essential property) or if initialization fails.*/void afterPropertiesSet() throws Exception;}
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 class DataSourceTransactionManager extends AbstractPlatformTransactionManagerimplements ResourceTransactionManager, InitializingBean {Nullableprivate DataSource dataSource;private boolean enforceReadOnly false;/*** Create a new DataSourceTransactionManager instance.* A DataSource has to be set to be able to use it.* see #setDataSource*/public DataSourceTransactionManager() {setNestedTransactionAllowed(true);}/*** Create a new DataSourceTransactionManager instance.* param dataSource JDBC DataSource to manage transactions for*/public DataSourceTransactionManager(DataSource dataSource) {this();setDataSource(dataSource);afterPropertiesSet();}Overridepublic void afterPropertiesSet() {if (getDataSource() null) {throw new IllegalArgumentException(Property dataSource is required);}}}InitializingBean接口的afterPropertiesSet()在AbstractAutowireCapableBeanFactoryinvokeInitMethods方法里被调用。 protected void invokeInitMethods(String beanName, final Object bean, Nullable RootBeanDefinition mbd)throws Throwable {boolean isInitializingBean (bean instanceof InitializingBean);// 执行InitializingBean的afterPropertiesSet()if (isInitializingBean (mbd null || !mbd.isExternallyManagedInitMethod(afterPropertiesSet))) {if (logger.isDebugEnabled()) {logger.debug(Invoking afterPropertiesSet() on bean with name beanName );}if (System.getSecurityManager() ! null) {try {AccessController.doPrivileged((PrivilegedExceptionActionObject) () - {((InitializingBean) bean).afterPropertiesSet();return null;}, getAccessControlContext());}catch (PrivilegedActionException pae) {throw pae.getException();}}else {// 执行InitialingBean的afterProperties()接口。((InitializingBean) bean).afterPropertiesSet();}}if (mbd ! null bean.getClass() ! NullBean.class) {String initMethodName mbd.getInitMethodName();if (StringUtils.hasLength(initMethodName) !(isInitializingBean afterPropertiesSet.equals(initMethodName)) !mbd.isExternallyManagedInitMethod(initMethodName)) {invokeCustomInitMethod(beanName, bean, mbd);}}} 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 Object initializeBean(final String beanName, final Object bean, Nullable RootBeanDefinition mbd) {if (System.getSecurityManager() ! null) {AccessController.doPrivileged((PrivilegedActionObject) () - {invokeAwareMethods(beanName, bean);return null;}, getAccessControlContext());}else {// 1. 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);}// 2. 执行所有的BeanPostProcessor里的postProcessBeforeInitialization()Object wrappedBean bean;if (mbd null || !mbd.isSynthetic()) {wrappedBean applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);}try {// 3. 执行Init方法, 其中包含InitializingBean接口里的AfterPropertiesSet()方法和自定义的init()方法invokeInitMethods(beanName, wrappedBean, mbd);}catch (Throwable ex) {throw new BeanCreationException((mbd ! null ? mbd.getResourceDescription() : null),beanName, Invocation of init method failed, ex);}//4. 执行所有的BeanPostProcessor的postProcessAfterInitialization()方法if (mbd null || !mbd.isSynthetic()) {wrappedBean applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);}return wrappedBean;}
