spring 注解--bean 的生命周期

1. 生命周期

创建 -> init -> destroy

2. 定义生命周期的方法

1. @Bean指定init-method和destroy-method
2. 实现InitializingBean和DisposableBean接口
3. 使用JSR250里面定义的注解：@PostConstruct（标注在方法上的，对象创建并赋值之后调用）；@PreDestroy（bean销毁之前调用）
4. 使用BeanPostProcessor，实现接口里的方法；（工作在初始化前后）

3. 实例

1. @Bean 里面的initMethod 和destroyMethod

@Configuration
public class MyBeanLifeCycle {
    @Scope(scopeName = "singleton")
    @Bean(name = "car", initMethod = "init", destroyMethod = "destroy")
    public Car getCar() {
        return new Car();
    }
}

2.InitializingBean和DisposableBean接口

public class Person implements InitializingBean, DisposableBean {
    public Person() {
        System.out.println("person constructor");
    }
    @Override
    public void destroy() throws Exception {
        System.out.println("person destroy");
    }
    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("person init");
    }
}

3. @PostConstruct和@PreDestroy注解

public class Student {
    public Student() {
        System.out.println("student constructor");
    }
    @PostConstruct
    public void init() {
        System.out.println("student init");
    }
    @PreDestroy
    public void destroy() {
        System.out.println("student destroy");
    }

4. 使用BeanPostProcessor. (为所有的bean初始化前后，添加处理方法)

public class BeanProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessBeforeInitialization ===>" + beanName);
        return bean;
    }
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessAfterInitialization ===>" + beanName);
        return bean;
    }
}

Note: 当定义的bean是单例时，当容器关闭时，相应的bean也会自动销毁；如果bean是prototype时，bean不会自动销毁。