Spring底层原理学习笔记--第三讲--(bean生命周期与模板方法)

bean生命周期

A03Application.java

package com.lucifer.itheima.a03; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.context.ConfigurableApplicationContext; @SpringBootApplication public class A03Application { public static void main(String[] args) { //执行结果为 // 2023-11-06 10:41:10.761 INFO 54360 --- [ main] com.lucifer.itheima.a03.LifeCycleBean : 构造 // 2023-11-06 10:41:10.764 INFO 54360 --- [ main] com.lucifer.itheima.a03.LifeCycleBean : 依赖注入 // 2023-11-06 10:41:10.765 INFO 54360 --- [ main] com.lucifer.itheima.a03.LifeCycleBean : 初始化 // 2023-11-06 10:41:11.060 INFO 54360 --- [ main] com.lucifer.itheima.a03.LifeCycleBean : 销毁 ConfigurableApplicationContext context = SpringApplication.run(A03Application.class); context.close(); } }

LifeCycleBean.java

package com.lucifer.itheima.a03; import lombok.extern.slf4j.Slf4j; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; @Component @Slf4j public class LifeCycleBean { public LifeCycleBean(){ log.info("构造"); } @Autowired public void autowire(@Value("${JAVA_HOME}") String home) { log.info("依赖注入：{}",home); } @PostConstruct public void init() { log.info("初始化"); } @PreDestroy public void destroy(){ log.info("销毁"); } }

MyBeanPostProcessor.java

package com.lucifer.itheima.a03; import lombok.extern.slf4j.Slf4j; import org.springframework.beans.BeansException; import org.springframework.beans.PropertyValues; import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor; import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor; import org.springframework.stereotype.Component; @Component @Slf4j //执行结果为 //2023-11-06 11:50:39.728 INFO 47300 --- [ main] c.l.itheima.a03.MyBeanPostProcessor : <<<<<<实例化之前执行，这里返回的对象会替换掉原来的bean // 2023-11-06 11:50:39.730 INFO 47300 --- [ main] com.lucifer.itheima.a03.LifeCycleBean : 构造 // 2023-11-06 11:50:39.732 INFO 47300 --- [ main] c.l.itheima.a03.MyBeanPostProcessor : <<<<<<实例化之后，这里如果返回false会跳过依赖注入阶段 // 2023-11-06 11:50:39.732 INFO 47300 --- [ main] c.l.itheima.a03.MyBeanPostProcessor : <<<<<<初始化之前执行，这里返回的对象会替换掉原来的bean，如PostConstruct，@ConfigurationProperties //2023-11-06 11:50:39.732 INFO 47300 --- [ main] com.lucifer.itheima.a03.LifeCycleBean : 初始化 // 2023-11-06 11:50:39.732 INFO 47300 --- [ main] c.l.itheima.a03.MyBeanPostProcessor : <<<<<<初始化之后执行，这里返回的对象会替换掉原来的bean，如代理增强 // 2023-11-06 11:50:40.034 INFO 47300 --- [ main] c.l.itheima.a03.MyBeanPostProcessor : <<<<<<销毁之前执行，如@PreDestroy //2023-11-06 11:50:40.035 INFO 47300 --- [ main] com.lucifer.itheima.a03.LifeCycleBean : 销毁 public class MyBeanPostProcessor implements InstantiationAwareBeanPostProcessor, DestructionAwareBeanPostProcessor { @Override public void postProcessBeforeDestruction(Object bean,String beanName) throws BeansException{ if (beanName.equals("lifeCycleBean")) log.info("<<<<<<销毁之前执行，如@PreDestroy"); } @Override public Object postProcessBeforeInstantiation(Class<?> beanClass,String beanName) throws BeansException{ if (beanName.equals("lifeCycleBean")){ log.info("<<<<<<实例化之前执行，这里返回的对象会替换掉原来的bean"); } // 返回null的话就不会替换掉原来的对象 return null; } @Override public boolean postProcessAfterInstantiation(Object bean,String beanName) throws BeansException{ if (beanName.equals("lifeCycleBean")) { log.info("<<<<<<实例化之后，这里如果返回false会跳过依赖注入阶段"); return false; } return true; } @Override public PropertyValues postProcessProperties(PropertyValues pvs,Object bean,String beanName) throws BeansException{ if (beanName.equals("lifeCycleBean")) { log.info("<<<<<<依赖注入阶段执行，如@Autowired，@Value，@Resource"); } return pvs; } @Override public Object postProcessBeforeInitialization(Object bean,String beanName) throws BeansException{ if (beanName.equals("lifeCycleBean")) { log.info("<<<<<<初始化之前执行，这里返回的对象会替换掉原来的bean，如PostConstruct，@ConfigurationProperties"); } return bean; } @Override public Object postProcessAfterInitialization(Object bean,String beanName) throws BeansException{ if (beanName.equals("lifeCycleBean")){ log.info("<<<<<<初始化之后执行，这里返回的对象会替换掉原来的bean，如代理增强"); } return bean; } } 模板方法 package com.lucifer.itheima.a03; import java.util.ArrayList; import java.util.List; public class TestMethodTemplate { public static void main(String[] args) { MyBeanFactory beanFactory = new MyBeanFactory(); beanFactory.addBeanPostProcessor(bean-> System.out.println("解析 @Autowired")); beanFactory.addBeanPostProcessor(bean-> System.out.println("解析 @Resource")); beanFactory.getBean(); } // 模板方法 Template Method Pattern static class MyBeanFactory { public Object getBean() { Object bean = new Object(); System.out.println("构造 "+bean); System.out.println("依赖注入 "+ bean); // @Autowired,@Resource for (BeanPostProcessor processor : processors) { processor.inject(bean); } System.out.println("初始化 "+bean); return bean; } private List<BeanPostProcessor> processors = new ArrayList<>(); public void addBeanPostProcessor(BeanPostProcessor processor) { processors.add(processor); } } static interface BeanPostProcessor{ public void inject(Object bean); //对依赖注入阶段的扩展 } }