一步步剖析spring bean生命周期

2019 年 10 月 14 日
筆記

關於spring bean的生命周期，是深入學習spring的基礎，也是難點，本篇文章將採用程式碼+圖文結論的方式來闡述spring bean的生命周期，

本篇文章將闡述清楚下圖。

一項目結構及源碼

1.程式目錄結構

2.applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>  <beans xmlns="http://www.springframework.org/schema/beans"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">        <bean class="com.demo.dao.UserDao" id="userDao" scope="singleton" init-method="myInit" destroy-method="myDestroy">          <property name="userName" value="Alan_beijing"/>      </bean>        <bean class="com.demo.dao.MyBeanPostProcessor" id="myBeanPostProcessor"/>    </beans>

3.UserDao.java

package com.demo.dao;    import org.springframework.beans.BeansException;  import org.springframework.beans.factory.*;  import org.springframework.beans.factory.config.BeanPostProcessor;  import org.springframework.context.ApplicationContext;  import org.springframework.context.ApplicationContextAware;  import org.apache.log4j.Logger;    public class UserDao implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, InitializingBean,          DisposableBean{        private String userName;      private int count = 0;        public String getUserName() {          return userName;      }        //2.屬性注入，注入屬性為userName      public void setUserName(String userName) {          count++;          System.out.println(count + "：注入屬性userName="+userName);          this.userName = userName;      }        //1.無參構造函數，實例化時調用該構造函數      public UserDao() {          count++;          System.out.println(count + "：調用構造函數UserDao()");      }        //3.實現BeanNameAware，獲取bean id      public void setBeanName(String s) {          count++;          System.out.println(count + "：調用setBeanName()獲取bean id,bean id=" + s);      }        //4.實現BeanFactoryAware,獲取bean工廠      public void setBeanFactory(BeanFactory beanFactory) throws BeansException {          count++;          System.out.println(count + "：調用setBeanFactory()獲取bean工廠,beanFactory=" + beanFactory);      }        //5.實現ApplicationContextAware,獲取bean上下文      public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {          count++;          System.out.println(count + "：調用setApplicationContext()獲取bean上下文,applicationContext=" + applicationContext);      }        //6.實現InitializingBean，獲取afterPropertiesSet      public void afterPropertiesSet() throws Exception {          count++;          System.out.println(count + "：調用afterPropertiesSet()");      }        //7.自定義初始化方法myInit()      public void myInit() {          count++;          System.out.println(count + "：調用自定義myInit()");      }        //8.實現DisposableBean，獲取destroy()      public void destroy() throws Exception {          count++;          System.out.println(count + "：destroy()");      }        //9.自定義銷毀方法myDestroy()      public void myDestroy() {          count++;          System.out.println(count + "：調用自定義destroy()");      }  }

4.MyBeanPostProcessor.java

package com.demo.dao;    import org.springframework.beans.BeansException;  import org.springframework.beans.factory.config.BeanPostProcessor;    public  class MyBeanPostProcessor implements BeanPostProcessor {      public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {          System.out.println("=====調用postProcessBeforeInitialization()=====");          return bean;      }        public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {          System.out.println("=====調用postProcessAfterInitialization()=====");          return bean;      }  }

二測試程式碼及測試結果

1.test.java

package com.demo.test;    import com.demo.dao.UserDao;  import org.junit.Test;  import org.springframework.context.support.AbstractApplicationContext;  import org.springframework.context.support.ClassPathXmlApplicationContext;    public class MyTest {        @Test      public void test() {          //定義容器並初始化          //ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");          AbstractApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");          applicationContext.getBean(UserDao.class);          //只有關閉容器時，才會調用destroy方法          applicationContext.registerShutdownHook();      }  }