什么是Bean的生命周期,就是Bean从创建到销毁的过程。
springboot中Bean的生命周期的过程:
1.Bean的定义
2.Bean的初始化
3.Bean的生存期
4.Bean的销毁
Bean的生命周期过程描述:
首先Spring在实例化Bean的时候,会先调用它的构造函数,进行Bean的实例化,然后进行Bean的初始化,Bean的初始化过程经过三个阶段,初始化之前,初始化和初始化之后,这就是初始化过程,然后开始利用Bean经行业务逻辑处理,最后容器正常关闭,spring开始销毁Bean,Bean的销毁过程相对比较简单,调用DisposableBeanAdapter.destroy()方法,该方法有三个地方比较重要,分别出发Bean的生命周期方法,分别是:
1.processor.postProcessBeforeDestruction(this.bean,this.beanName);
2.((DisposableBean)bean).destroy();
3.invokeCustomDestroyMethod(this.destroyMethod);
实例演示:
User类,一个普通的Bean,用来添加到容器中,观察其生命周期
package com.itbofeng.bean;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
public class User implements InitializingBean , DisposableBean {
private String name;
public User() {
System.out.println("调用Bean的函数(constructor)");
}
public String getName() {
return name;
}
public void setName(String name) {
System.out.println("调用Bean的函数(setName/setAttribute)");
this.name = name;
}
@PostConstruct
public void postConstruct(){
System.out.println("调用Bean的函数(postConstruct)");
}
//MainConfig中@Bean 的initMethod
public void initMethod(){
System.out.println("调用Bean的函数(initMethod)");
}
//InitializingBean接口的方法afterPropertiesSet
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("调用Bean的函数(afterPropertiesSet)");
}
@PreDestroy
public void preDestroy(){
System.out.println("调用Bean的函数(preDestroy)");
}
//DisposableBean接口的方法destroy
@Override
public void destroy() throws Exception {
System.out.println("调用Bean的函数(destroy)");
}
//MainConfig中@Bean 的destroyMethod
public void destroyMethod(){
System.out.println("调用Bean的函数(destroyMethod)");
}
}
CustomBeanPostProcessor类,用来观察BeanPostProcessor的运行时期
package com.itbofeng.bean;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;
@Component
public class CustomBeanPostProcessor implements BeanPostProcessor {
@Nullable
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if(bean.getClass()==User.class){
System.out.println("调用postProcessBeforeInitialization...");
}
return bean;
}
@Nullable
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if(bean.getClass()==User.class){
System.out.println("调用postProcessAfterInitialization...");
}
return bean;
}
}
MainConfig类,springboot程序运行的主类,并将User和CunstomBeanPostProcessor加入到容器中
package com.itbofeng;
import com.itbofeng.bean.User;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
@SpringBootApplication
public class MainConfig {
public static void main(String[] args) {
SpringApplication.run(MainConfig.class,args);
}
@Bean(initMethod = "initMethod",destroyMethod = "destroyMethod")
public User user(){
return new User();
}
}
}
运行的结果为: