Spring源码：Bean生命周期（终章）

AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);

applicationContext.close();

import org.springframework.beans.factory.DisposableBean;
@Component
public class MyBean implements DisposableBean {

    @Override
    public void destroy() throws Exception {
        // 在这里清理资源
    }
}

import javax.annotation.PreDestroy;
@Component
public class MyBean {

    @PreDestroy
    public void cleanUp() throws Exception {
        // 在这里清理资源
    }
}

    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))));
    }

    public void destroySingleton(String beanName) {
        // Remove a registered singleton of the given name, if any.
        // 先从单例池中移除掉
        removeSingleton(beanName);

        // Destroy the corresponding DisposableBean instance.
        DisposableBean disposableBean;
        synchronized (this.disposableBeans) {
            disposableBean = (DisposableBean) this.disposableBeans.remove(beanName);
        }
        destroyBean(beanName, disposableBean);
    }