Spring Bean Life Cycle

backend

When container starts – a Spring bean needs to be instantiated, based on Java or XML bean definition. It may also be required to perform some post-initialization steps to get it into a usable state. Same bean life cycle is for spring boot applications as well.

前言

    Spring Bean的生命周期只有这四个阶段。把这四个阶段和每个阶段对应的扩展点糅合在一起虽然没有问题，但是这样非常凌乱，难以记忆。要彻底搞清楚Spring的生命周期，首先要把这四个阶段牢牢记住。实例化和属性赋值对应构造方法和setter方法的注入，初始化和销毁是用户能自定义扩展的两个阶段。在这四步之间穿插的各种扩展点。

Bean 四个阶段：

1).实例化 Instantiation
2).属性赋值 Populate
3).初始化 Initialization
4).销毁 Destruction

实例化 -> 属性赋值 -> 初始化 -> 销毁

Bean 的生命周期图示：


Bean的生命周期

准备对象：

UserLifeCycleTest-启动容器

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public class UserLifeCycleTest {

    public static void main(String[] args) {
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("lifecycle.xml");
        User user = applicationContext.getBean(User.class);
        System.out.println(user);
        //关闭IOC容器
        applicationContext.close();
    }
}

User-实体类：

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public class User implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, InitializingBean, DisposableBean {

    private String name;
    private int age;

    public User() {
        this.name = "laowang";
        this.age = 18;
        System.out.println("======== User Constructor ========");
    }

    public User(String name, int age) {
        this.name = name;
        this.age = age;
        System.out.println("======== User Constructor [name]" + name + " [age]" + age + " ========");
    }

    @Override
    public void setBeanName(String name) {
        System.out.println("======== User setBeanName【" + name + "】 ========");
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        System.out.println("======== User setBeanFactory【" + beanFactory + "】invoke ========");
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        System.out.println("======== User setApplicationContext【" + applicationContext + "】invoke ========");
    }

    //======== BeforeInitialization ========

    @PostConstruct
    public void postConstruct() {
        System.out.println("======== User postConstruct ========");
    }

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

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

    //======== AfterInitialization ========

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

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


    //-------------------getter,setter,toString start---------------

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    //-------------------getter,setter,toString end---------------

UserInstantiationAwareBeanPostProcessor-User处理类：

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public class UserInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor {
    @Override
    public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
        if (beanClass.equals(User.class)) {
            System.out.println("======== BeforeInstantiation beanClass【" + beanClass + "】" + "beanName【" + beanName + "】========");
        }
        return null;
    }

    @Override
    public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
        if (bean instanceof User) {
            System.out.println("======== AfterInstantiation bean【" + bean + "】" + "beanName【" + beanName + "】========");
        }
        return true;
    }

    @Override
    public PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {
        if (bean instanceof User) {
            System.out.println("======== PropertyValues【" + pvs + "】 PropertyDescriptor 【" + pds + "】 bean【" + bean + "】" + "beanName【" + beanName + "】========");
        }
        return pvs;
    }


    //----------------------------------以下是 BeanPostProcessor的方法 ----------------------------------

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (bean instanceof User) {
            System.out.println("======== BeforeInitialization bean【" + bean + "】" + "beanName【" + beanName + "】========");
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if (bean instanceof User) {
            System.out.println("======== AfterInitialization bean【" + bean + "】" + "beanName【" + beanName + "】========");
        }
        return bean;
    }
}

lifecycle.xml配置文件：

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

    <context:annotation-config />
y
    <bean id="user" class="com.arsenal.beanlifecycle.User" init-method="initMethod" destroy-method="destroyMethod"/>

    <bean id="userInstantiationAwareBeanPostProcessor"
          class="com.arsenal..UserInstantiationAwareBeanPostProcessor"/>

</beans>

执行顺序：

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======== BeforeInstantiation beanClass【class com.arsenal.beanlifecycle.User】beanName【user】========
======== User Constructor ========
======== AfterInstantiation bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
======== PropertyValues【PropertyValues: length=0】 PropertyDescriptor 【[Ljava.beans.PropertyDescriptor;@105fece7】 bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
======== User setBeanName【user】 ========
======== User setBeanFactory【org.springframework.beans.factory.support.DefaultListableBeanFactory@184f6be2: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,user,userInstantiationAwareBeanPostProcessor]; root of factory hierarchy】invoke ========
======== User setApplicationContext【org.springframework.context.support.ClassPathXmlApplicationContext@7dc36524: startup date [Sun Sep 20 16:16:22 CST 2020]; root of context hierarchy】invoke ========
======== BeforeInitialization bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
======== User postConstruct ========
======== User afterPropertiesSet ========
======== User initMethod ========
======== AfterInitialization bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
======== User PreDestroy ========
======== User destroy ========
======== User destroyMethod ========

执行详细信息：

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16:16:22.858 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'user'
16:16:22.858 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating instance of bean 'user'
======== BeforeInstantiation beanClass【class com.arsenal.beanlifecycle.User】beanName【user】========
======== User Constructor ========
16:16:22.860 [main] DEBUG org.springframework.context.annotation.CommonAnnotationBeanPostProcessor - Found init method on class [com.arsenal.beanlifecycle.User]: public void com.arsenal.beanlifecycle.User.postConstruct()
16:16:22.860 [main] DEBUG org.springframework.context.annotation.CommonAnnotationBeanPostProcessor - Found destroy method on class [com.arsenal.beanlifecycle.User]: public void com.arsenal.beanlifecycle.User.PreDestroy()
16:16:22.860 [main] DEBUG org.springframework.context.annotation.CommonAnnotationBeanPostProcessor - Registered init method on class [com.arsenal.beanlifecycle.User]: org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement@a1ab9f17
16:16:22.860 [main] DEBUG org.springframework.context.annotation.CommonAnnotationBeanPostProcessor - Registered destroy method on class [com.arsenal.beanlifecycle.User]: org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement@194fb3f7
16:16:22.860 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Eagerly caching bean 'user' to allow for resolving potential circular references
======== AfterInstantiation bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
======== PropertyValues【PropertyValues: length=0】 PropertyDescriptor 【[Ljava.beans.PropertyDescriptor;@105fece7】 bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
======== User setBeanName【user】 ========
======== User setBeanFactory【org.springframework.beans.factory.support.DefaultListableBeanFactory@184f6be2: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,user,userInstantiationAwareBeanPostProcessor]; root of factory hierarchy】invoke ========
======== User setApplicationContext【org.springframework.context.support.ClassPathXmlApplicationContext@7dc36524: startup date [Sun Sep 20 16:16:22 CST 2020]; root of context hierarchy】invoke ========
======== BeforeInitialization bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
16:16:22.864 [main] DEBUG org.springframework.context.annotation.CommonAnnotationBeanPostProcessor - Invoking init method on bean 'user': public void com.arsenal.beanlifecycle.User.postConstruct()
======== User postConstruct ========
16:16:22.864 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Invoking afterPropertiesSet() on bean with name 'user'
======== User afterPropertiesSet ========
16:16:22.864 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Invoking init method  'initMethod' on bean with name 'user'
======== User initMethod ========
======== AfterInitialization bean【com.arsenal.beanlifecycle.User@1b083826】beanName【user】========
16:16:22.864 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Finished creating instance of bean 'user'
16:16:22.864 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'userInstantiationAwareBeanPostProcessor'
16:16:22.865 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
16:16:22.881 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Unable to locate LifecycleProcessor with name 'lifecycleProcessor': using default [org.springframework.context.support.DefaultLifecycleProcessor@3ee0fea4]
16:16:22.882 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'lifecycleProcessor'
16:16:22.885 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Could not find key 'spring.liveBeansView.mbeanDomain' in any property source
16:16:22.888 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'user'
com.arsenal.beanlifecycle.User@1b083826
16:16:22.888 [main] INFO org.springframework.context.support.ClassPathXmlApplicationContext - Closing org.springframework.context.support.ClassPathXmlApplicationContext@7dc36524: startup date [Sun Sep 20 16:16:22 CST 2020]; root of context hierarchy
16:16:22.888 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'lifecycleProcessor'
16:16:22.889 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@184f6be2: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,user,userInstantiationAwareBeanPostProcessor]; root of factory hierarchy
16:16:22.889 [main] DEBUG org.springframework.context.annotation.CommonAnnotationBeanPostProcessor - Invoking destroy method on bean 'user': public void com.arsenal.beanlifecycle.User.PreDestroy()
======== User PreDestroy ========
16:16:22.889 [main] DEBUG org.springframework.beans.factory.support.DisposableBeanAdapter - Invoking destroy() on bean with name 'user'
======== User destroy ========
16:16:22.890 [main] DEBUG org.springframework.beans.factory.support.DisposableBeanAdapter - Invoking destroy method 'destroyMethod' on bean with name 'user'
======== User destroyMethod ========

延伸

    雷丰阳_spring源码
    SpringIoc 实现原理
    spring-bean-life-cycle
    Spring Bean的生命周期
    深究Spring中Bean的生命周期

Article Title:Spring Bean Life Cycle

Article Author:Funing Ma

Release Time:2020-09-19 18:18:18

Last Update:2020-09-24 23:06:42

Original Link:https://mafuning.github.io/2020/09/19/2020-09-19-Spring-Bean-Life-Cycle/

License Agreement: "CC-BY-SA-4.0"

Content
  1. 1. 前言
  2. 2. Bean的生命周期
  3. 3. 延伸