Spring bean lifecycle - A Spring bean that tap into various lifecycle extension points

MyApplicationTest.java

package org.piyush;

import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class MyApplicationTest {

	@Test
	public void contextLoads() {
	}

}

MySpringBean.java

package org.piyush;

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;

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

public class MySpringBean implements BeanNameAware,
        ApplicationContextAware,
        InitializingBean,
        DisposableBean {

    private String message;

    public void sendMessage(String message) {
        this.message = message;
    }

    public String getMessage() {
        return this.message;
    }

    @Override
    public void setBeanName(String name) {
        // BeanNameAware#setBeanName
        System.out.println("--- BeanNameAware#setBeanName executed ---");
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
        // ApplicationContextAware#setApplicationContext
        System.out.println("--- ApplicationContextAware#setApplicationContext executed ---");
    }

    @PostConstruct
    public void postConstruct() {
        System.out.println("--- JSR-250 - @PostConstruct executed ---");
    }

    @Override
    public void afterPropertiesSet() {
        // IntializingBean#afterPropertiesSet
        System.out.println("--- IntializingBean#afterPropertiesSet executed ---");
    }

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

    @PreDestroy
    public void preDestroy() {
        System.out.println("--- JSR-250 - @PreDestroy executed ---");
    }

    @Override
    public void destroy() throws Exception {
        // DisposableBean#destroy
        System.out.println("--- DisposableBean#destroy executed ---");
    }

    public void destroyMethod() {
        System.out.println("--- destroy-method executed ---");
    }
}

MySpringBeanFactoryPostProcessor.java

package org.piyush;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.stereotype.Component;

@Component
public class MySpringBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
        System.out.println("--- MySpringBeanFactoryPostProcessor#postProcessBeanFactory ---");

        final BeanDefinition mySpringBean = configurableListableBeanFactory.getBeanDefinition("mySpringBean");

        System.out.println(mySpringBean.getFactoryBeanName()); // appConfig
        System.out.println(mySpringBean.getInitMethodName());  // init
    }
}

MySpringBeanPostProcessor.java

package org.piyush;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;

// BeanPostProcessor has to be a bean too, that is why it is annotated as @Component.
@Component
public class MySpringBeanPostProcessor implements BeanPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        if (bean instanceof MySpringBean) {
            System.out.println("--- postProcessBeforeInitialization executed ---");
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
        if (bean instanceof MySpringBean) {
            System.out.println("--- postProcessAfterInitialization executed ---");
        }
        return bean;
    }

}

MySpringConfiguration.java

package org.piyush;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class AppConfig {
    // We can alternatively annotate MySpringBean with @Component to create bean.
    @Bean(initMethod = "init", destroyMethod = "destroy")
    public MySpringBean mySpringBean(){
        return new MySpringBean();
    }
}

The order of execution is as follows:

--- MySpringBeanFactoryPostProcessor#postProcessBeanFactory ---
appConfig
init
--- BeanNameAware#setBeanName executed ---
--- ApplicationContextAware#setApplicationContext executed ---
--- MySpringBeanPostProcessor#postProcessBeforeInitialization executed ---
--- JSR-250 - @PostConstruct executed ---
--- InitializingBean#afterPropertiesSet executed ---
--- Bean#init-method executed ---
--- MySpringBeanPostProcessor#postProcessAfterInitialization executed ---
--- JSR-250 - @PreDestroy executed ---
--- Bean#destroy executed ---