spring学习总结006 --- Bean级生命周期接口

spring提供的Bean级生命周期接口有BeanNameAware、BeanFactoryAware、InitializingBean、DisposableBean；

1、BeanNameAware和BeanFactoryAware

BeanNameAware接口用于为实现了该接口的Bean设置BeanName；BeanFactoryAware接口用于为实现了该接口的bean设置BeanFactory；

这两个接口实际应用场景是什么呢？这两个接口可以通过静态方法在应用程序任意位置获取Bean

示例：

@Component
public class SpringBeanUtil implements BeanNameAware, BeanFactoryAware {

    private static String beanName;

    private static BeanFactory beanFactory;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        SpringBeanUtil.beanFactory = beanFactory;
    }

    @Override
    public void setBeanName(String name) {
        SpringBeanUtil.beanName = name;
    }

    public static <T> T getBean(Class<T> tClass) {
        return Objects.nonNull(beanFactory) ? beanFactory.getBean(tClass) : null;
    }

    public static String getCurrentBeanName() {
        return beanName;
    }
}

@Slf4j
public class Test2 {
    public static void main(String[] args) {
        new ClassPathXmlApplicationContext("classpath:bean2.xml");

        log.info("Aware bean name: {}", SpringBeanUtil.getCurrentBeanName());

        log.info("SpringBeanUtil get user bean: {}", SpringBeanUtil.getBean(User.class));
    }
}

运行结果：

那么BeanNameAware.setBeanName方法和BeanFactoryAware.setBeanFactory方法是什么时候被调用的呢？在初始化bean时调用

AbstractApplicationContext.finishBeanFactoryInitialization  ----->

DefaultListableBeanFactory.preInstantiateSingletons ------>

AbstractBeanFactory.getBean  -------->

AbstractBeanFactory.doGetBean  -------->

AbstractAutowireCapableBeanFactory.createBean  ------->

AbstractAutowireCapableBeanFactory.doCreateBean  ------->

AbstractAutowireCapableBeanFactory.initializeBean   ------->

AbstractAutowireCapableBeanFactory.invokeAwareMethods   ------->

2、InitializingBean和DisposableBean

实现InitializingBean接口的bean在bean初始化时执行afterPropertiesSet方法，类似于bean定义指定的init-method方法；

实现DisposableBean接口的bean在bean销毁时执行destroy方法，类似于bean定义时指定的destory-method方法；

实现接口bean的优先级高于bean定义指定的方法

示例：

@Slf4j
@ToString
public class InitDestroyBean implements InitializingBean, DisposableBean {

    private String desc;

    public void initMethod() {
        log.info("Invoke init method.");
    }

    public void destroyMethod() {
        log.info("Invoke destroy method.");
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        log.info("Invoke afterPropertiesSet....");
        this.desc = "Test initializing bean...";
    }

    @Override
    public void destroy() throws Exception {
        log.info("Invoke destroy....");
    }
}

@Slf4j
public class Test3 {

    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:bean3.xml");

        log.warn("InitDestroyBean: {}", context.getBean(InitDestroyBean.class));

        context.destroy();
    }
}

<bean class="com.demo.bean.InitDestroyBean" init-method="initMethod" destroy-method="destroyMethod" />

执行结果：