整理在Spring IOC容器初始化后可以处理特定逻辑的多种实现方式

　　Spring框架的核心是依赖注入、切面；Spring Boot是在Spring框架的基础上为其提供许多默认配置、默认约定（约定优于配置），从而达到减少或减化配置进而可开箱即用、快速上手；Spring Cloud又是在Spring Boot框架的基础上提供了大量的微服务体系内的各种组件（starter），简化了微服务开发实现的成本；但不管是Spring、Spring Boot、Spring Cloud的底层实现都是充分利用了IOC、AOP；有时我们想在所有Bean都成功注册到IOC容器后，并实例化完成后统一做一些初始化的工作，那么就需要捕获Spring IOC容器初始化后的事件点，而这个事件点我结合自己经验及网上分享进行了一次整理汇总，主要是有如下几种方式（先后触发顺序）：

1. ApplicationContextAware.setApplicationContext
2. Bean 添加了@PostConstruct的方法
3. InitializingBean.afterPropertiesSet
4. BeanPostProcessor （postProcessBeforeInitialization、postProcessAfterInitialization）
5. SmartLifecycle.start
6. ApplicationListener.onApplicationEvent
7. ApplicationRunner.run

下面是把如上的触发点都集中实现在一个Bean中看效果，示例代码如下：

package cn.zuowenjun.demo.ioc.service;

import cn.zuowenjun.demo.ioc.mapper.DemoInfoMapper;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationListener;
import org.springframework.context.SmartLifecycle;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;
import org.springframework.web.context.WebApplicationContext;

import javax.annotation.PostConstruct;
import java.util.Date;

@Component
public class DemoModesCollection
        implements ApplicationContextAware,
        ApplicationListener<ContextRefreshedEvent>,
        ApplicationRunner,
        SmartLifecycle,
        InitializingBean,
        BeanPostProcessor {

    private  ApplicationContext context;

    @PostConstruct
    public void postConstructMethod(){
        System.out.printf("%1$tF %1$tT.%1$tL --->@PostConstruct postConstructMethod:running!%n",new Date());
        DemoInfoMapper mapper= context.getBean(DemoInfoMapper.class);

        System.out.println("@PostConstruct >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.printf("%1$tF %1$tT.%1$tL --->InitializingBean.afterPropertiesSet:running!%n",new Date());
        DemoInfoMapper mapper= context.getBean(DemoInfoMapper.class);
        System.out.println("afterPropertiesSet >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        System.out.printf("%1$tF %1$tT.%1$tL --->ApplicationContextAware.setApplicationContext:running! ===beansCount:%2$d %n",
                new Date(), applicationContext.getBeanDefinitionCount());
        this.context=applicationContext;
        DemoInfoMapper mapper= context.getBean(DemoInfoMapper.class);
        System.out.println("setApplicationContext >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
    }

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {

        if (event.getApplicationContext().getParent() == null || event.getApplicationContext() instanceof WebApplicationContext) {
            System.out.printf("%1$tF %1$tT.%1$tL --->ApplicationListener.onApplicationEvent:running! ===beansCount:%2$d  (beanType:%3$s) %n",
                    new Date(), event.getApplicationContext().getBeanDefinitionCount(), event.getApplicationContext().getClass().getTypeName());

            DemoInfoMapper mapper= event.getApplicationContext().getBean(DemoInfoMapper.class);
            System.out.println("onApplicationEvent >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
        }
    }

    @Override
    public void run(ApplicationArguments args) throws Exception {
        System.out.printf("%1$tF %1$tT.%1$tL --->ApplicationRunner.run:running!%n", new Date());
        DemoInfoMapper mapper= context.getBean(DemoInfoMapper.class);
        System.out.println("run >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
    }

    private boolean isRunning = false;

    @Override
    public void start() {

        System.out.printf("%1$tF %1$tT.%1$tL --->SmartLifecycle.start:running!%n",new Date());

        isRunning=true;

        DemoInfoMapper mapper= context.getBean(DemoInfoMapper.class);
        System.out.println("start >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
    }

    @Override
    public void stop() {
        isRunning = false;
    }

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

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.printf("%1$tF %1$tT.%1$tL --->BeanPostProcessor.postProcessBeforeInitialization:running!%n",new Date());
        DemoInfoMapper mapper= context.getBean(DemoInfoMapper.class);
        System.out.println("postProcessBeforeInitialization >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.printf("%1$tF %1$tT.%1$tL --->BeanPostProcessor.postProcessAfterInitialization:running!%n",new Date());
        DemoInfoMapper mapper= context.getBean(DemoInfoMapper.class);
        System.out.println("postProcessAfterInitialization >>>context.getBean:" + (mapper==null?"null":AopUtils.getTargetClass(mapper).getName()));
        return bean;
    }
}

　如上代码，大家可将尝试其加入到一个spring boot项目中，就可以看到运行的效果（执行的顺序）　，比如我这里的输出如下：

2019-11-16 12:25:48.283 --->ApplicationContextAware.setApplicationContext:running! ===beansCount:325
setApplicationContext >>>context.getBean:com.sun.proxy.$Proxy84
2019-11-16 12:25:48.558 --->@PostConstruct postConstructMethod:running!
@PostConstruct >>>context.getBean:com.sun.proxy.$Proxy84
2019-11-16 12:25:48.559 --->InitializingBean.afterPropertiesSet:running!
afterPropertiesSet >>>context.getBean:com.sun.proxy.$Proxy84
2019-11-16 12:25:48.567 --->BeanPostProcessor.postProcessBeforeInitialization:running!
postProcessBeforeInitialization >>>context.getBean:com.sun.proxy.$Proxy84
2019-11-16 12:25:48.567 --->BeanPostProcessor.postProcessAfterInitialization:running!
......有很多的BeanPostProcessor.postProcessBeforeInitialization、BeanPostProcessor.postProcessAfterInitialization（每一个bean初始化前后都会触发，省略）
2019-11-16 12:25:50.045 --->SmartLifecycle.start:running!
start >>>context.getBean:com.sun.proxy.$Proxy84
2019-11-16 12:25:50.053 --->ApplicationListener.onApplicationEvent:running! ===beansCount:325 (beanType:org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext)
onApplicationEvent >>>context.getBean:com.sun.proxy.$Proxy84
2019-11-16 12:25:50.080 --->ApplicationRunner.run:running!
run >>>context.getBean:com.sun.proxy.$Proxy84

从输出结果我们可以看出整个的顺序，那么也得出结论最好是在：SmartLifecycle.start、ApplicationListener.onApplicationEvent、ApplicationRunner.run 这三种实现方式中才能真正达到IOC初始后全部完成后触发的事件点的要求。

注：如果需要在控制台直接看到上面的内容，建议调整spring root的log level，避免无效的日志输出影响观看，配置如：

logging.level.root=error