聊聊DisposableBeanAdapter

聊聊DisposableBeanAdapter

序

本文主要研究一下DisposableBeanAdapter

DisposableBean

spring-beans/src/main/java/org/springframework/beans/factory/DisposableBean.java

public interface DisposableBean {/*** Invoked by the containing {@code BeanFactory} on destruction of a bean.* @throws Exception in case of shutdown errors. Exceptions will get logged* but not rethrown to allow other beans to release their resources as well.*/void destroy() throws Exception;}

DisposableBean定义了destroy方法

DisposableBeanAdapter

spring-beans/src/main/java/org/springframework/beans/factory/support/DisposableBeanAdapter.java

class DisposableBeanAdapter implements DisposableBean, Runnable, Serializable {private static final String CLOSE_METHOD_NAME = "close";private static final String SHUTDOWN_METHOD_NAME = "shutdown";private static final Log logger = LogFactory.getLog(DisposableBeanAdapter.class);private final Object bean;private final String beanName;private final boolean invokeDisposableBean;private final boolean nonPublicAccessAllowed;@Nullableprivate final AccessControlContext acc;@Nullableprivate String destroyMethodName;@Nullableprivate transient Method destroyMethod;@Nullableprivate final List<DestructionAwareBeanPostProcessor> beanPostProcessors;@Overridepublic void run() {destroy();}@Overridepublic void destroy() {if (!CollectionUtils.isEmpty(this.beanPostProcessors)) {for (DestructionAwareBeanPostProcessor processor : this.beanPostProcessors) {processor.postProcessBeforeDestruction(this.bean, this.beanName);}}if (this.invokeDisposableBean) {if (logger.isTraceEnabled()) {logger.trace("Invoking destroy() on bean with name '" + this.beanName + "'");}try {if (System.getSecurityManager() != null) {AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {((DisposableBean) this.bean).destroy();return null;}, this.acc);}else {((DisposableBean) this.bean).destroy();}}catch (Throwable ex) {String msg = "Invocation of destroy method failed on bean with name '" + this.beanName + "'";if (logger.isDebugEnabled()) {logger.warn(msg, ex);}else {logger.warn(msg + ": " + ex);}}}if (this.destroyMethod != null) {invokeCustomDestroyMethod(this.destroyMethod);}else if (this.destroyMethodName != null) {Method methodToInvoke = determineDestroyMethod(this.destroyMethodName);if (methodToInvoke != null) {invokeCustomDestroyMethod(ClassUtils.getInterfaceMethodIfPossible(methodToInvoke));}}}/*** Check whether the given bean has any kind of destroy method to call.* @param bean the bean instance* @param beanDefinition the corresponding bean definition*/public static boolean hasDestroyMethod(Object bean, RootBeanDefinition beanDefinition) {if (bean instanceof DisposableBean || bean instanceof AutoCloseable) {return true;}return inferDestroyMethodIfNecessary(bean, beanDefinition) != null;}/*** If the current value of the given beanDefinition's "destroyMethodName" property is* {@link AbstractBeanDefinition#INFER_METHOD}, then attempt to infer a destroy method.* Candidate methods are currently limited to public, no-arg methods named "close" or* "shutdown" (whether declared locally or inherited). The given BeanDefinition's* "destroyMethodName" is updated to be null if no such method is found, otherwise set* to the name of the inferred method. This constant serves as the default for the* {@code @Bean#destroyMethod} attribute and the value of the constant may also be* used in XML within the {@code <bean destroy-method="">} or {@code* <beans default-destroy-method="">} attributes.* <p>Also processes the {@link java.io.Closeable} and {@link java.lang.AutoCloseable}* interfaces, reflectively calling the "close" method on implementing beans as well.*/@Nullableprivate static String inferDestroyMethodIfNecessary(Object bean, RootBeanDefinition beanDefinition) {String destroyMethodName = beanDefinition.resolvedDestroyMethodName;if (destroyMethodName == null) {destroyMethodName = beanDefinition.getDestroyMethodName();if (AbstractBeanDefinition.INFER_METHOD.equals(destroyMethodName) ||(destroyMethodName == null && bean instanceof AutoCloseable)) {// Only perform destroy method inference or Closeable detection// in case of the bean not explicitly implementing DisposableBeandestroyMethodName = null;if (!(bean instanceof DisposableBean)) {try {destroyMethodName = bean.getClass().getMethod(CLOSE_METHOD_NAME).getName();}catch (NoSuchMethodException ex) {try {destroyMethodName = bean.getClass().getMethod(SHUTDOWN_METHOD_NAME).getName();}catch (NoSuchMethodException ex2) {// no candidate destroy method found}}}}beanDefinition.resolvedDestroyMethodName = (destroyMethodName != null ? destroyMethodName : "");}return (StringUtils.hasLength(destroyMethodName) ? destroyMethodName : null);}	
}	

DisposableBeanAdapter实现了DisposableBean、Runnable接口，其run方法执行的是destroy方法；其destroy方法会遍历DestructionAwareBeanPostProcessor挨个执行postProcessBeforeDestruction方法，对于invokeDisposableBean的则执行其destroy方法，对于destroyMethod不为null或者destroyMethodName不为null的则通过invokeCustomDestroyMethod执行

它提供了hasDestroyMethod方法用于判断某个bean是否有destroy方法，如果是DisposableBean或者AutoCloseable类型则直接返回true，否则通过inferDestroyMethodIfNecessary方法判断，它目前会把public的无参的close或者shutdown方法(不论是自己定义的还是继承而来的)作为destroyMethod

registerDisposableBeanIfNecessary

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

	/*** Add the given bean to the list of disposable beans in this factory,* registering its DisposableBean interface and/or the given destroy method* to be called on factory shutdown (if applicable). Only applies to singletons.* @param beanName the name of the bean* @param bean the bean instance* @param mbd the bean definition for the bean* @see RootBeanDefinition#isSingleton* @see RootBeanDefinition#getDependsOn* @see #registerDisposableBean* @see #registerDependentBean*/protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null);if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {if (mbd.isSingleton()) {// Register a DisposableBean implementation that performs all destruction// work for the given bean: DestructionAwareBeanPostProcessors,// DisposableBean interface, custom destroy method.registerDisposableBean(beanName, new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessorCache().destructionAware, acc));}else {// A bean with a custom scope...Scope scope = this.scopes.get(mbd.getScope());if (scope == null) {throw new IllegalStateException("No Scope registered for scope name '" + mbd.getScope() + "'");}scope.registerDestructionCallback(beanName, new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessorCache().destructionAware, acc));}}}protected boolean requiresDestruction(Object bean, RootBeanDefinition mbd) {return (bean.getClass() != NullBean.class && (DisposableBeanAdapter.hasDestroyMethod(bean, mbd) ||(hasDestructionAwareBeanPostProcessors() && DisposableBeanAdapter.hasApplicableProcessors(bean, getBeanPostProcessorCache().destructionAware))));}

AbstractBeanFactory的registerDisposableBeanIfNecessary方法会通过requiresDestruction判断是否需要销毁，是的话会执行registerDisposableBean或者registerDestructionCallback，这里通过DisposableBeanAdapter进行了包装

小结

DisposableBeanAdapter实现了DisposableBean、Runnable接口，它主要是执行DestructionAwareBeanPostProcessor的postProcessBeforeDestruction方法，对于invokeDisposableBean的则执行其destroy方法，对于destroyMethod不为null或者destroyMethodName不为null的则通过invokeCustomDestroyMethod执行。

DisposableBeanAdapter提供了hasDestroyMethod方法用于判断某个bean是否有destroy方法，如果是DisposableBean或者AutoCloseable类型则直接返回true，否则通过inferDestroyMethodIfNecessary方法判断，它目前会把public的无参的close或者shutdown方法(不论是自己定义的还是继承而来的)作为destroyMethod

值得注意的是自动推断的前提是beanDefinition.getDestroyMethodName()为AbstractBeanDefinition.INFER_METHOD或者是destroyMethodName为null但是bean是AutoCloseable类型，而且推断也只是找close、shutdown方法，如果没有实现DisposableBean接口，但是定义了destory方法，不会被认为是destroyMethod；@Bean注解的destroyMethod默认就是AbstractBeanDefinition.INFER_METHOD，如果是通过GenericApplicationContext.registerBean注册的，则默认destroyMethodName为空，需要自己设置，如果是通过registerBeanDefinition方法的，需要自己保证destroyMethodName为想要执行的销毁方法。