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本文主要研究一下DisposableBeanAdapter
DisposableBean
spring-beans/src/main/java/org/springframework/beans/factory/DisposableBean.java
代码语言：javascript复制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
代码语言：javascript复制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;
@Nullable
private final AccessControlContext acc;
@Nullable
private String destroyMethodName;
@Nullable
private transient Method destroyMethod;
@Nullable
private final List<DestructionAwareBeanPostProcessor> beanPostProcessors;
@Override
public void run() {
destroy();
}
@Override
public 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.
*/
@Nullable
private 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 DisposableBean
destroyMethodName = 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
代码语言：javascript复制 /**
* 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。
