Spring与bean有关的生命周期示例详解

前言

记得以前的时候，每次提起Spring中的bean相关的生命周期时，内心都无比的恐惧，因为好像有很多，自己又理不清楚：什么beanFactory啊，aware接口啊，beanPostProcessor啊，afterPropertiesSet啊，initMethod啊等等。

今天终于理清这些关系了，并且又新增了对postConstruct和lifecycle的理解。

执行顺序

- 首先是 BeanFactoryPostProcessor，它是针对所有bean的definition的，只执行一次

下面是针对每个bean的初始

• - 实现了一系列aware接口的，比如BeanNameAware，ApplicationContextAware，调用其set方法
• - 执行BeanPostProcessor的postProcessBeforeInitialization方法
• - 带有@PostConstruct注解的方法
• - 实现InitializingBean接口的afterPropertiesSet方法
• - 指定的initMethod方法
• - 执行BeanPostProcessor的postProcessAfterInitialization方法
• - 实现了SmartLifecycle接口的start方法(实现Lifecycle接口的不会自动调用，需要显式的调用start方法)

下面是针对每个bean的销毁

• - 实现了SmartLifecycle接口的stop方法(实现Lifecycle接口的不会自动调用，需要显式的调用stop方法)
• - 带有@PreDestroy注解的方法
• - 实现DisposableBean接口的destroy方法
• - 指定的destroyMethod方法

目前就想到这么多了，其他的麻烦在评论区留言呀~

代码实例

bean实体类

/**
 * @date: 2020-07-22
 * 
 * 一个简单的枚举类 
 */
public enum BeanType {
  NORMAL, LIFECYCLE, SMART_LIFECYCLE;
}

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
/**
 * @author: lihui
 * @date: 2020-07-22
 * 一个简单的bean
 */
@Slf4j
public class NormalBean implements BeanNameAware, ApplicationContextAware, InitializingBean, DisposableBean {
  private BeanType beanType;

  public NormalBean() {
    this(BeanType.NORMAL);
  }

  public NormalBean(BeanType beanType) {
    this.beanType = beanType;
  }

  @PostConstruct
  public void postConstruct() {
    log.info("{}, postConstruct", beanType);
  }

  @Override
  public void afterPropertiesSet() throws Exception {
    log.info("{}, afterPropertiesSet", beanType);
  }

  public void initMethod() {
    log.info("{}, initMethod", beanType);
  }

  @PreDestroy
  public void preDestroy() {
    log.info("{}, preDestroy", beanType);
  }

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

  public void destroyMethod() {
    log.info("{}, destroyMethod", beanType);
  }

  @Override
  public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    log.info("setApplicationContext, applicationContext : {}", applicationContext);
  }

  @Override
  public void setBeanName(String name) {
    log.info("setBeanName, bean name : {}", name);
  }
}

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.Lifecycle;
/**
 * @author: lihui
 * @date: 2020-07-22
 * 实现了Lifecycle的一个bean
 */
@Slf4j
public class LifecycleBean extends NormalBean implements Lifecycle {
  private volatile boolean running = false;

  public LifecycleBean() {
    super(BeanType.LIFECYCLE);
  }

  @Override
  public void start() {
    log.info("start");
    running = true;
  }

  @Override
  public void stop() {
    log.info("stop");
    running = false;
  }

  @Override
  public boolean isRunning() {
    return running;
  }
}

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.SmartLifecycle;
/**
 * @author: lihui
 * @date: 2020-07-22
 * 实现了SmartLifecycle的一个bean
 */
@Slf4j
public class SmartLifecycleBean extends NormalBean implements SmartLifecycle {
  private volatile boolean running = false;

  public SmartLifecycleBean() {
    super(BeanType.SMART_LIFECYCLE);
  }

  @Override
  public void start() {
    log.info("start");
    running = true;
  }

  @Override
  public void stop() {
    log.info("stop");
    running = false;
  }

  @Override
  public boolean isRunning() {
    return running;
  }
}

配置类

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
/**
 * @author: lihui
 * @date: 2020-07-25
 */
@Slf4j
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
  @Override
  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    log.info("postProcessBeanFactory, beanFactory:{}", beanFactory);
  }
}

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
/**
 * @author: lihui
 * @date: 2020-07-25
 */
@Slf4j
public class MyBeanPostProcessor implements BeanPostProcessor {
  @Override
  public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    log.info("postProcessBeforeInitialization, bean:{}", beanName);
    return bean;
  }

  @Override
  public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    log.info("postProcessAfterInitialization, bean:{}", beanName);
    return bean;
  }
}

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.SmartLifecycle;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
 * @author: lihui
 * @date: 2020-07-22
 */
@Configuration
@Slf4j
public class Config {

  @Bean(initMethod = "initMethod", destroyMethod = "destroyMethod")
  public NormalBean normalBean() {
    return new NormalBean();
  }

  @Bean(initMethod = "initMethod", destroyMethod = "destroyMethod")
  public LifecycleBean lifecycleBean() {
    return new LifecycleBean();
  }

  @Bean(initMethod = "initMethod", destroyMethod = "destroyMethod")
  public SmartLifecycle smartLifecycle() {
    return new SmartLifecycleBean();
  }

  @Bean
  public static MyBeanFactoryPostProcessor myBeanFactoryPostProcessor() {
    return new MyBeanFactoryPostProcessor();
  }

  @Bean
  public static MyBeanPostProcessor myBeanPostProcessor() {
    return new MyBeanPostProcessor();
  }
}

Main类

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * @author: lihui
 * @date: 2020-07-22
 */
@Slf4j
public class Main {
  public static void main(String[] args) throws InterruptedException {
    ConfigurableApplicationContext ctx = new AnnotationConfigApplicationContext(Config.class);
    ctx.registerShutdownHook();
    Thread.sleep(5000);
    log.info("line ----------------------------- line");
    ctx.start();
    ctx.stop();
    log.info("line ----------------------------- line");
  }
}

结果说明

结果正如前面所说的执行顺序一致，主要注意的就是Lifecycle接口和SmartLifecycle接口，只有实现了SmartLifecycle接口的bean在初始化时才会被自动调用，而实现了Lifecycle接口的除非显式调用start和stop方法才会被调用。

总结

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