Spring Bean的一生

When you work directly in Java, you can do anything you like with your objects and do not always need to rely on the container lifecycle.

前言:

在Ioc容器启动后相应的Bean并没有立即实例化，此时Ioc容器仅仅拥有所有对象的BeanDefinition(Bean对象在Spring中的描述,包含该Bean在容器中实例化所需的信息，通过解析xml/javaconfig后所得)

Spring Bean生命周期的管理

Spring bean factory能管理Beans的生命周期，通过实现InitializingBean和DisposableBean

这两个接口都只声明一个方法让我们可以初始化/关闭bean中的资源

当然在整个生命周期中也提供了一些Call Back Methods,这些方法类似于Servlet中的监听器的实现

• 当Bean处于post-initialization阶段时，我们可以通过实现InitializingBean接口来实现afterPropertiesSet()
• 当Bean处于pre-destruction阶段时，我们可以实现DisposableBean接口来实现destroy()方法

Spring Bean的生命周期图

Code Time

以Rick类交给Spring容器管理，方法顺序为其在Spring容器中的执行顺序

Rick.java

public class Rick implements InitializingBean, DisposableBean {
    public Rick(){
        System.out.println("Rick is in [Rick] - Rick()");
    }

    public void customInit(){
        System.out.println("Rick is in [Rick] - customInit()");
    }

    @PostConstruct
    public void postConstruct(){
        System.out.println("Rick is in [@PostConstruct] - postConstruct()");
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("Rick is in [InitializingBean] - afterPropertiesSet()");
    }

    @PreDestroy
    public void preDestroy(){
        System.out.println("Rick is in [@PreDestroy] - preDestroy()");
    }

    @Override
    public void destroy() throws Exception {
        System.out.println("Rick is in [DisposableBean] - destroy()");
    }

    public void customDestroy(){
        System.out.println("Rick is in [Rick] - customDestroy()");
    }
}

加入BeanPostProcess

RickBeanPostProcess.java

public class RickBeanPostProcess implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (bean instanceof Rick) {
            System.out.println("Rick is in [BeanPostProcessor] - postProcessBeforeInitialization()");
        }

        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if (bean instanceof Rick) {
            System.out.println("Rick is in [BeanPostProcessor] - postProcessAfterInitialization()");
        }
        return bean;
    }
}

配置类

RickConfig.java

@Configuration
public class RickConfig {

    /**
     * 指定自定义初始化方法和自定义销毁方法
     * @return Rick
     */
    @Bean(initMethod = "customInit",destroyMethod = "customDestroy")
    public Rick rick(){
        return new Rick();
    }

    @Bean
    public RickBeanPostProcess rickBeanPostProcess(){
        return new RickBeanPostProcess();
    }
}

测试类

Client.java

public class Client {
    public static void main(String[] args) {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(RickConfig.class);
        ((AnnotationConfigApplicationContext) applicationContext).close();
    }
}

最终结果如下

Rick is in [Rick] - Rick()
Rick is in [BeanPostProcessor] - postProcessBeforeInitialization()
Rick is in [@PostConstruct] - postConstruct()
Rick is in [InitializingBean] - afterPropertiesSet()
Rick is in [Rick] - customInit()
Rick is in [BeanPostProcessor] - postProcessAfterInitializa
Rick is in [@PreDestroy] - preDestroy()
Rick is in [DisposableBean] - destroy()
Rick is in [Rick] - customDestroy()

参考

Spring Framework Documentation

Spring Bean Life Cycle Explained

Spring Bean Life Cycle

Spring Boot Bean生命周期

Spring的Bean生命周期理解

Spring Bean的一生

原文：https://www.cnblogs.com/xcmelody/p/11080452.html