钩子Aware

Spring中有大量的很多Aware接口，给使用者提供ioc容器中各个阶段的感知方式

Aware.png

例如

• ApplicationStartupAware接口的bean就将会在容器启动的时候触发
• BeanFactoryAware将会在给Bean设置beanFactory的时候触发
  通过这些钩子函数，使用者能够根据需要，在恰当时机去做某些事，或者拿到需要使用的容器中的对象。

与Bean相关的：

• BeanFactoryAware
• BeanClassLoaderAware
• BeanNameAware

Bean生命周期相关的

改造ServiceA如下：

package com.test.service;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanNameAware;

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

/**
 * @author felix
 */
public class ServiceA implements BeanFactoryAware, BeanNameAware, BeanClassLoaderAware {
    public ServiceA() {
        System.out.println("constructor");
    }

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

    public void init() {
        System.out.println("init");
    }

    public void destroy() {
        System.out.println("destroy");
    }

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

    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        System.out.println("setBeanFactory:" + beanFactory.getClass());
    }

    public void setBeanName(String beanName) {
        System.out.println("setBeanName:" + beanName);
    }

    public void setBeanClassLoader(ClassLoader classLoader) {
        System.out.println("setBeanClassLoader:" + classLoader.getClass());
    }

    public String doSth() {
        System.out.println("serviceA doSth");
        // throw new RuntimeException("an exception ");
        return "hello";
    }
}

改造BootConfig.java如下：

package com.test;

import com.test.service.ServiceA;
import org.springframework.beans.BeansException;
import org.springframework.context.*;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.core.metrics.ApplicationStartup;

/**
 * @author felix
 */
@Configuration
@ComponentScan(basePackages = "com.test")
@EnableAspectJAutoProxy
public class BootConfig implements ApplicationStartupAware, ApplicationContextAware, ApplicationEventPublisherAware {
    @Bean(initMethod = "init", destroyMethod = "destroy")
    public ServiceA getServiceA() {
        return new ServiceA();
    }

    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        System.out.println("setApplicationContext: " + applicationContext.getClass());
    }

    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        System.out.println("setApplicationEventPublisher: " + applicationEventPublisher);
    }

    public void setApplicationStartup(ApplicationStartup applicationStartup) {
        System.out.println("setApplicationStartup" + applicationStartup);
    }
}

启动测试类，结果如下：

setApplicationEventPublisher: org.springframework.context.annotation.AnnotationConfigApplicationContext@8807e25, started on Thu Sep 09 10:41:43 CST 2021
setApplicationStartuporg.springframework.core.metrics.DefaultApplicationStartup@77fbd92c
setApplicationContext: class org.springframework.context.annotation.AnnotationConfigApplicationContext
constructor
setBeanName:getServiceA
setBeanClassLoader:class sun.misc.Launcher$AppClassLoader
setBeanFactory:class org.springframework.beans.factory.support.DefaultListableBeanFactory
post construct
init
serviceA doSth
preDestroy
destroy

可以看到：

• 1.ApplicationEventPublisherAware生效，通过实现该接口，我们能在setApplicationEventPublisher方法拿到applicationEventPublisher，这个对象是用来向容器发布一些事件的
• 2.ApplicationStartupAware生效
• 3.ApplicationContextAware生效，这一步说明ApplicationContext已经创建了，我们可以拿到这个实例
• 4.执行了ServiceA的构造方法，说明这一步已经在实例化bean了
• 5.setBeanName bean处理，生成好了bean的名称
• 6.setBeanClassLoader bean处理，生成了bean的ClassLoader
• 7.setBeanFactory bean处理，设置BeanFactory
• 8.bean构造函数后置方法，容器对bean的赋能差不多了，该干点自己想干的事了
• 9.bean initMethod配置的初始化方法
• 10.bean业务代码
• 11.bean preDestroy
• 12.destroy