Bean生命周期流程

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一、Bean生命周期流程图

1. spring启动，加载类路径下配置文件，解析为BeanDefinition并装配到对应容器中；
2. 查找并加载spring管理的bean，进行bean的实例化；
3. Bean实例化后对Bean的引用和值进行属性注入；
4. 若Bean实现接口BeanNameAware，则执行setBeanName()方法，获取bean的名字；
5. 若Bean实现接口BeanFactoryAware，则执行setBeanFactory()方法，获取BeanFactory;
6. 若Bean实现接口ApplicationContextAware，则执行setApplicationContext()方法，获取应用上下文；
7. 若Bean实现BeanPostProcessor接口，则先执行postProcessBeforeInitialization()方法；
8. 若Bean实现InitializingBean接口，则执行afterPropertiesSet()方法；
9. 若Bean配置了init-method方法，则执行自定义方法；
10. 若Bean实现BeanPostProcessor接口，则先执行postProcessAfterInitialization()方法；
11. 如Bean实现了DisposableBean接口，则容器销毁时则执行destory()方法；
12. 如果Bean配置了destory-method，则容器销毁时则执行自定义方法。

二、验证流程

1.验证UserDao生命周期

代码如下（示例）：

/**
 * @program: spring
 * @description:
 * @author: kerry
 * @date: 2021-10-09 14:06
 **/
public class UserDao implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, InitializingBean, DisposableBean {


	public User getUserById() {
		return new User(123456L, "kerry");
	}

	@Override
	public void setBeanName(String name) {
		System.out.println("setBeanName:" + name);
	}

	@Override
	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		System.out.println("setBeanFactory");
	}

	@Override
	public void destroy() throws Exception {
		System.out.println("destroy");
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		System.out.println("afterPropertiesSet");
	}

	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		System.out.println("setApplicationContext");
	}

	@PostConstruct
	public void testPostConstruct() {
		System.out.println("testPostConstruct");
	}

	@PreDestroy
	public void testPreDestroy() {
		System.out.println("testPreDestroy");
	}

	@Override
	protected void finalize() throws Throwable {
		System.out.println("finalize");
	}


	public void initMethod() {
		System.out.println("initMethod");
	}

	public void destroyMethod() {
		System.out.println("destroyMethod");
	}
}

2.自定义MyBeanFactoryPostProcessor

代码如下（示例）：

/**
 * @program: spring
 * @description:
 * @author: kerry
 * @date: 2021-10-09 17:02
 **/
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {


	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		Object obj = beanFactory.getBean("userService");
		if (Objects.nonNull(obj) && obj instanceof UserService) {
			System.out.println("postProcessBeanFactory " + ((UserService) obj).getUserById(123));
		}

		System.out.println("postProcessBeanFactory");
	}
}

3.自定义MyBeanPostProcessor

代码如下（示例）：

/**
 * @program: spring
 * @description:
 * @author: kerry
 * @date: 2021-10-09 16:59
 **/
public class MyBeanPostProcessor implements BeanPostProcessor {

	@Override
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		if (bean instanceof UserDao) {
			System.out.println("postProcessBeforeInitialization");
		}
		return bean;
	}


	@Override
	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
		if (bean instanceof UserDao) {
			System.out.println("postProcessAfterInitialization");
		}
		return bean;
	}
}

4.配置文件

代码如下（示例）：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


	<bean class="com.kerry.test.processor.MyBeanFactoryPostProcessor"></bean>
	<bean class="com.kerry.test.processor.MyBeanPostProcessor"></bean>

	<bean id="userDao" class="com.kerry.test.dao.UserDao" init-method="initMethod" destroy-method="destroyMethod"></bean>

	<bean id="userService" class="com.kerry.test.service.impl.UserServiceImpl"></bean>
	
</beans>

5.测试类

代码如下（示例）：

/**
 * @program: spring
 * @description:
 * @author: kerry
 * @date: 2021-09-30 14:29
 **/
public class Test {
	public static void main(String[] args) {
		System.out.println("************容器启动开始*************");

		ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"spring-context.xml"});
		UserService userService = (UserService) context.getBean("userService");
		User user = userService.getUserById(12345);

		if (context instanceof AbstractApplicationContext) {
			((AbstractApplicationContext) context).registerShutdownHook();
		}

		System.out.println("************容器启动成功*************");


		/*AnnotationConfigApplicationContext annotationConfigApplicationContext = new
				AnnotationConfigApplicationContext(AppConfig.class);

		UserDao userDao = annotationConfigApplicationContext.getBean(UserDao.class);
		User user = userDao.getUserById();
		System.out.println(user.toString());
*/
	}
}

测试结果如下：

************容器启动开始*************
postProcessBeanFactory User{userId=12345, name='kerry'}
postProcessBeanFactory
setBeanName:userDao
setBeanFactory
setApplicationContext
postProcessBeforeInitialization
afterPropertiesSet
initMethod
postProcessAfterInitialization
************容器启动成功*************
destroy
destroyMethod

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三、总结

以上是对Spring中bean的核心接口和生命周期的总结和验证，其实生命周期中还有其他很多操作感兴趣的小伙伴可以自行下载Spring源码研究下。