轉自https://www.jianshu.com/p/8e2d400492c7
Bean的生命週期過程描述
我們先看一下Bean的生命週期過程中都會經歷些什麼,我先簡單解釋一下,後面我們通過源碼進行詳細解釋。首先Spring在實例化Bean的時候,會先調用它的構造函數,進行Bean的實例化,然後進行Bean的初始化,Bean的初始化經過三個階段初始化之前(applyBeanPostProcessorsBeforeInitialization),其次是進行初始化(invokeInitMethods),最後是初始化之後(postProcessAfterInitialization),這就是Bean的初始化過程;然後就開始利用Bean進行業務邏輯處理,最後容器正常關閉,Spring開始銷燬Bean,Bean的銷燬過程相對比較簡單,調用DisposableBeanAdapter.destroy()方法,該方法中有三個地方比較重要,分別觸發Bean的生命週期方法,它們是:processor.postProcessBeforeDestruction(this.bean, this.beanName);
((DisposableBean) bean).destroy();
invokeCustomDestroyMethod(this.destroyMethod);
下面我把用圖片來進行直觀展示:
實例運行
User類,這裏就是普通的一個Bean,用來添加到容器中,觀察其生命週期
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("調用Bean的函數(constructor)");
}
public String getName() {
return name;
}
public void setName(String name) {
System.out.println("調用Bean的函數(setName/setAttribute)");
this.name = name;
}
@PostConstruct
public void postConstruct(){
System.out.println("調用Bean的函數(postConstruct)");
}
//MainConfig中@Bean 的initMethod
public void initMethod(){
System.out.println("調用Bean的函數(initMethod)");
}
//InitializingBean接口的方法afterPropertiesSet
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("調用Bean的函數(afterPropertiesSet)");
}
@PreDestroy
public void preDestroy(){
System.out.println("調用Bean的函數(preDestroy)");
}
//DisposableBean接口的方法destroy
@Override
public void destroy() throws Exception {
System.out.println("調用Bean的函數(destroy)");
}
//MainConfig中@Bean 的destroyMethod
public void destroyMethod(){
System.out.println("調用Bean的函數(destroyMethod)");
}
}
CustomBeanPostProcessor類,用來觀察BeanPostProcessor的運行時期
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("調用postProcessBeforeInitialization...");
}
return bean;
}
@Nullable
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if(bean.getClass()==User.class){
System.out.println("調用postProcessAfterInitialization...");
}
return bean;
}
}
MainConfig類,SpringBoot程序運行的主類,並將User和CustomBeanPostProcessor 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();
}
}
運行結果