Bean的生命周期

Posted 2021-08-31 保护眼睛

Bean的生命周期

• • • 总结
    • 示例

总结

1.Spring启动，查找并加载需要被Spring管理的bean，进行Bean的实例化
2.Bean实例化后对将Bean的引入和值注入到Bean的属性中
3.如果Bean实现了BeanNameAware接口的话，Spring将Bean的Id传递给setBeanName()方法
4.如果Bean实现了BeanFactoryAware接口的话，Spring将调用setBeanFactory()方法，将BeanFactory容器实例传入
5.如果Bean实现了ApplicationContextAware接口的话，Spring将调用Bean的setApplicationContext()方法，将bean所在应用上下文引用传入进来
6.如果Bean实现了BeanPostProcessor接口，Spring就将调用他们的postProcessBeforeInitialization()方法。
7.如果Bean 实现了InitializingBean接口，Spring将调用他们的afterPropertiesSet()方法。类似的，如果bean使用init-method声明了初始化方法，该方法也会被调用
8.如果Bean 实现了BeanPostProcessor接口，Spring就将调用他们的postProcessAfterInitialization()方法。
9.此时，Bean已经准备就绪，可以被应用程序使用了。他们将一直驻留在应用上下文中，直到应用上下文被销毁。
10.如果bean实现了DisposableBean接口，Spring将调用它的destory()接口方法，同样，如果bean使用了destory-method 声明销毁方法，该方法也会被调用。

示例

package org.example.BeanLife;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.*;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

public class LifeCycleTest implements InitializingBean, DisposableBean,
        ApplicationContextAware, BeanNameAware, BeanFactoryAware {
    public void beanInit() {

        System.out.println("init-method: 注解是使用@Bean(initMethod=\\"方法名\\") 的方式，xml是使用<bean init-method=\\"方法名\\" />");
    }

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

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("InitializingBean");
    }
    
    public void beanDestroy() {
        System.out.println("destroy-method: 注解是使用@Bean(destroyMethod=\\"方 法名\\")的方式，xml是使用<bean destroy-method=\\"方法名\\" />");
    }

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

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

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

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

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

package org.example;

import org.example.BeanLife.LifeCycleTest;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class AppConfig implements BeanPostProcessor {
    @Bean(initMethod = "beanInit", destroyMethod = "beanDestroy")
    public LifeCycleTest lifeCycleTest() {
        return new LifeCycleTest();
    }

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

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