Bean的初始化干预方式二

1. 代码示例

2. 自定义初始化操作

org.springframework.beans.factory.InitializingBean对beanFactory设置过的属性进行校验或者添加自定义初始化。

/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory;

/**
 * Interface to be implemented by beans that need to react once all their properties
 * have been set by a {@link BeanFactory}: e.g. to perform custom initialization,
 * or merely to check that all mandatory properties have been set.
 *
 * <p>An alternative to implementing {@code InitializingBean} is specifying a custom
 * init method, for example in an XML bean definition. For a list of all bean
 * lifecycle methods, see the {@link BeanFactory BeanFactory javadocs}.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see DisposableBean
 * @see org.springframework.beans.factory.config.BeanDefinition#getPropertyValues()
 * @see org.springframework.beans.factory.support.AbstractBeanDefinition#getInitMethodName()
 */
public interface InitializingBean {

	/**
	 * Invoked by the containing {@code BeanFactory} after it has set all bean properties
	 * and satisfied {@link BeanFactoryAware}, {@code ApplicationContextAware} etc.
	 * <p>This method allows the bean instance to perform validation of its overall
	 * configuration and final initialization when all bean properties have been set.
	 * @throws Exception in the event of misconfiguration (such as failure to set an
	 * essential property) or if initialization fails for any other reason
	 */
	void afterPropertiesSet() throws Exception;

}

3. 自定义销毁操作

org.springframework.beans.factory.DisposableBean在bean销毁时释放资源。ApplicationContext在关闭时会释放所有的单实例bean。言下之意，Spring容器不负责多实例的销毁工作。

/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory;

/**
 * Interface to be implemented by beans that want to release resources on destruction.
 * A {@link BeanFactory} will invoke the destroy method on individual destruction of a
 * scoped bean. An {@link org.springframework.context.ApplicationContext} is supposed
 * to dispose all of its singletons on shutdown, driven by the application lifecycle.
 *
 * <p>A Spring-managed bean may also implement Java's {@link AutoCloseable} interface
 * for the same purpose. An alternative to implementing an interface is specifying a
 * custom destroy method, for example in an XML bean definition. For a list of all
 * bean lifecycle methods, see the {@link BeanFactory BeanFactory javadocs}.
 *
 * @author Juergen Hoeller
 * @since 12.08.2003
 * @see InitializingBean
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getDestroyMethodName()
 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory#destroySingletons()
 * @see org.springframework.context.ConfigurableApplicationContext#close()
 */
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;

}