Spring Bean 的生命週期在整個 Spring 中佔有很重要的位置,掌握這些能夠加深對 Spring 的理解。java
首先看下生命週期圖:spring
再談生命週期以前有一點須要先明確:app
Spring 只幫咱們管理單例模式 Bean 的完整生命週期,對於 prototype 的 bean ,Spring 在建立好交給使用者以後則不會再管理後續的生命週期。ide
在 bean 初始化時會經歷幾個階段,首先能夠使用註解 @PostConstruct
, @PreDestroy
來在 bean 的建立和銷燬階段進行調用:post
@Component public class AnnotationBean { private final static Logger LOGGER = LoggerFactory.getLogger(AnnotationBean.class); @PostConstruct public void start(){ LOGGER.info("AnnotationBean start"); } @PreDestroy public void destroy(){ LOGGER.info("AnnotationBean destroy"); } }
還能夠實現 InitializingBean,DisposableBean
這兩個接口,也是在初始化以及銷燬階段調用:this
@Service public class SpringLifeCycleService implements InitializingBean,DisposableBean{ private final static Logger LOGGER = LoggerFactory.getLogger(SpringLifeCycleService.class); @Override public void afterPropertiesSet() throws Exception { LOGGER.info("SpringLifeCycleService start"); } @Override public void destroy() throws Exception { LOGGER.info("SpringLifeCycleService destroy"); } }
也能夠自定義方法用於在初始化、銷燬階段調用:prototype
@Configuration public class LifeCycleConfig { @Bean(initMethod = "start", destroyMethod = "destroy") public SpringLifeCycle create(){ SpringLifeCycle springLifeCycle = new SpringLifeCycle() ; return springLifeCycle ; } } public class SpringLifeCycle{ private final static Logger LOGGER = LoggerFactory.getLogger(SpringLifeCycle.class); public void start(){ LOGGER.info("SpringLifeCycle start"); } public void destroy(){ LOGGER.info("SpringLifeCycle destroy"); } }
以上是在 SpringBoot 中能夠這樣配置,若是是原始的基於 XML 也是能夠使用:rest
<bean class="com.crossoverjie.spring.SpringLifeCycle" init-method="start" destroy-method="destroy"> </bean>
來達到一樣的效果。code
*Aware
接口能夠用於在初始化 bean 時得到 Spring 中的一些對象,如獲取 Spring 上下文
等。server
@Component public class SpringLifeCycleAware implements ApplicationContextAware { private final static Logger LOGGER = LoggerFactory.getLogger(SpringLifeCycleAware.class); private ApplicationContext applicationContext ; @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext ; LOGGER.info("SpringLifeCycleAware start"); } }
這樣在 springLifeCycleAware
這個 bean 初始化會就會調用 setApplicationContext
方法,並能夠得到 applicationContext
對象。
實現 BeanPostProcessor 接口,Spring 中全部 bean 在作初始化時都會調用該接口中的兩個方法,能夠用於對一些特殊的 bean 進行處理:
@Component public class SpringLifeCycleProcessor implements BeanPostProcessor { private final static Logger LOGGER = LoggerFactory.getLogger(SpringLifeCycleProcessor.class); /** * 預初始化 初始化以前調用 * @param bean * @param beanName * @return * @throws BeansException */ @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { if ("annotationBean".equals(beanName)){ LOGGER.info("SpringLifeCycleProcessor start beanName={}",beanName); } return bean; } /** * 後初始化 bean 初始化完成調用 * @param bean * @param beanName * @return * @throws BeansException */ @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { if ("annotationBean".equals(beanName)){ LOGGER.info("SpringLifeCycleProcessor end beanName={}",beanName); } return bean; } }
執行以後觀察結果:
018-03-21 00:40:24.856 [restartedMain] INFO c.c.s.p.SpringLifeCycleProcessor - SpringLifeCycleProcessor start beanName=annotationBean 2018-03-21 00:40:24.860 [restartedMain] INFO c.c.spring.annotation.AnnotationBean - AnnotationBean start 2018-03-21 00:40:24.861 [restartedMain] INFO c.c.s.p.SpringLifeCycleProcessor - SpringLifeCycleProcessor end beanName=annotationBean 2018-03-21 00:40:24.864 [restartedMain] INFO c.c.s.aware.SpringLifeCycleAware - SpringLifeCycleAware start 2018-03-21 00:40:24.867 [restartedMain] INFO c.c.s.service.SpringLifeCycleService - SpringLifeCycleService start 2018-03-21 00:40:24.887 [restartedMain] INFO c.c.spring.SpringLifeCycle - SpringLifeCycle start 2018-03-21 00:40:25.062 [restartedMain] INFO o.s.b.d.a.OptionalLiveReloadServer - LiveReload server is running on port 35729 2018-03-21 00:40:25.122 [restartedMain] INFO o.s.j.e.a.AnnotationMBeanExporter - Registering beans for JMX exposure on startup 2018-03-21 00:40:25.140 [restartedMain] INFO com.crossoverjie.Application - Started Application in 2.309 seconds (JVM running for 3.681) 2018-03-21 00:40:25.143 [restartedMain] INFO com.crossoverjie.Application - start ok! 2018-03-21 00:40:25.153 [Thread-8] INFO o.s.c.a.AnnotationConfigApplicationContext - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@3913adad: startup date [Wed Mar 21 00:40:23 CST 2018]; root of context hierarchy 2018-03-21 00:40:25.155 [Thread-8] INFO o.s.j.e.a.AnnotationMBeanExporter - Unregistering JMX-exposed beans on shutdown 2018-03-21 00:40:25.156 [Thread-8] INFO c.c.spring.SpringLifeCycle - SpringLifeCycle destroy 2018-03-21 00:40:25.156 [Thread-8] INFO c.c.s.service.SpringLifeCycleService - SpringLifeCycleService destroy 2018-03-21 00:40:25.156 [Thread-8] INFO c.c.spring.annotation.AnnotationBean - AnnotationBean destroy
直到 Spring 上下文銷燬時則會調用自定義的銷燬方法以及實現了 DisposableBean
的 destroy()
方法。