spring中的Lifecycle

Lifecycle介绍

Lifecycle是spring中的生命循环接口，实现该接口的类将会可以启动，关闭。在AbstractApplicationContext通过ConfigurableApplicationContext接口中就实现了Lifecycle，当上下文调用start()函数时，就会去BeanFactory中找实现了Lifecycle接口的Bean，并调用该bean的start()函数。

AbstractApplicationContext源码分析

初始化LifecycleProcessor

AbstractApplicationContext中有方法initLifecycleProcessor()，用来初始化生命周期执行器，用以执行容器中所有实现了Lifecycle接口的bean。

/*** Initialize the LifecycleProcessor.* Uses DefaultLifecycleProcessor if none defined in the context.* @see org.springframework.context.support.DefaultLifecycleProcessor*/
protected void initLifecycleProcessor() {ConfigurableListableBeanFactory beanFactory = getBeanFactory();//参试在容器中获取LifecycleProcessorif (beanFactory.containsLocalBean(LIFECYCLE_PROCESSOR_BEAN_NAME)) {this.lifecycleProcessor =beanFactory.getBean(LIFECYCLE_PROCESSOR_BEAN_NAME, LifecycleProcessor.class);if (logger.isTraceEnabled()) {logger.trace("Using LifecycleProcessor [" + this.lifecycleProcessor + "]");}}else {//容器没有则使用DefaultLifecycleProcessorDefaultLifecycleProcessor defaultProcessor = new DefaultLifecycleProcessor();//设置BeanFactory，因为要对BeanFactory里面的Lifecycle bean调用start,stopdefaultProcessor.setBeanFactory(beanFactory);this.lifecycleProcessor = defaultProcessor;//注册到容器中beanFactory.registerSingleton(LIFECYCLE_PROCESSOR_BEAN_NAME, this.lifecycleProcessor);if (logger.isTraceEnabled()) {logger.trace("No '" + LIFECYCLE_PROCESSOR_BEAN_NAME + "' bean, using " +"[" + this.lifecycleProcessor.getClass().getSimpleName() + "]");}}
}

start()和stop()

AbstractApplicationContext中的start()和stop()方法用来启动生命周期。通过LifecycleProcessor来去启动BeanFactory中的实现了Lifecycle接口的bean。

//---------------------------------------------------------------------
// Implementation of Lifecycle interface
//---------------------------------------------------------------------@Override
public void start() {getLifecycleProcessor().start();publishEvent(new ContextStartedEvent(this));
}@Override
public void stop() {getLifecycleProcessor().stop();publishEvent(new ContextStoppedEvent(this));
}

DefaultLifecycleProcessor源码分析

start()和startBeans()

DefaultLifecycleProcessor通过从BeanFactory中获取LifecycleBean，并调用它们的start()方法

@Override
public void start() {startBeans(false);this.running = true;
}// Internal helpersprivate void startBeans(boolean autoStartupOnly) {//这里是从BeanFactory中获取所有LifecycleBeanMap<String, Lifecycle> lifecycleBeans = getLifecycleBeans();Map<Integer, LifecycleGroup> phases = new HashMap<>();lifecycleBeans.forEach((beanName, bean) -> {if (!autoStartupOnly || (bean instanceof SmartLifecycle && ((SmartLifecycle) bean).isAutoStartup())) {int phase = getPhase(bean);LifecycleGroup group = phases.get(phase);if (group == null) {group = new LifecycleGroup(phase, this.timeoutPerShutdownPhase, lifecycleBeans, autoStartupOnly);phases.put(phase, group);}group.add(beanName, bean);}});if (!phases.isEmpty()) {List<Integer> keys = new ArrayList<>(phases.keySet());Collections.sort(keys);for (Integer key : keys) {//最后会调用该bean的start()方法phases.get(key).start();}}
}

Lifecycle Bean使用示例

MyLifecycleBean

/*** @author liangwy * @since 2022-5-17*/
public class MyLifecycleBean implements Lifecycle {private Boolean flag = false;@Overridepublic void start() {this.flag = true;System.out.println("启动MyLifecycleBean");}@Overridepublic void stop() {this.flag = false;System.out.println("关闭MyLifecycleBean");}@Overridepublic boolean isRunning() {return flag;}
}

测试

public static void main(String[] args) {AnnotationConfigApplicationContext applicationContext = runAnnotationConfigApplicationContext();applicationContext.start();MyLifecycleBean myLifecycleBean = applicationContext.getBean("myLifecycleBean", MyLifecycleBean.class);System.out.println(myLifecycleBean.isRunning());applicationContext.stop();System.out.println(myLifecycleBean.isRunning());
}/*** 注解配置方式创建上下文* @return*/
public static AnnotationConfigApplicationContext runAnnotationConfigApplicationContext(){AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(ApplicationMain.class);applicationContext.getBeanFactory().registerCustomEditor(Date.class,TestPropertyEditorSupport.class);return applicationContext;
}

结果打印

启动MyLifecycleBean
true
关闭MyLifecycleBean
false