淺談spring bean生命週期

關於spring bean的生命週期，是深入學習spring的基礎，也是難點，本篇文章將採用代碼+圖文結論的方式來闡述spring bean的生命週期，本篇文章將闡述清楚下圖。

一項目結構及源碼

1.程序目錄結構

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，注入屬性爲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.自定義銷燬方法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;
    }
}

二測試代碼及測試結果

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，纔會調用destroy方法
        applicationContext.registerShutdownHook();
    }
}

2.測試結果