Spring(三)--Bean生命周期

基本概念

在Spring中，可以从两个层面定义Bean的生命周期，第一个层面是Bean的作用范围；第二个层面是实例化Bean时所经历的一系列阶段。

BeanFactory中Bean的生命周期

1.生命周期过程图解

生命周期图解

假设一个Bean实现了所有的接口，大的概况一下Bean的生命周期：

1.实例化BeanFactoryPostProcessor：处理的对象是BeanFactory级别

2.实例化BeanPostProcessor实现类

3.实例化InstantiationAwareBeanPostProcessorAdapter实现类，注：该类是BeanPostProcessor的扩展

4.执行InstantiationAwareBeanPostProcessorAdapter类的postProcessBeforeInstantiation方法

5.Bean的构造方法

6.执行InstantiationAwareBeanPostProcessorAdapter类的postProcessPropertyValues

7.为Bean注入属性，即依赖注入

8.调用BeanNameAware的setBeanName方法

9.调用BeanNameAware的setBeanFactory方法

10.执行BeanPostProcessor的后置处理器，postProcessAfterInitialization方法

11.调用InitializingBean的afterPropertiesSet方法

12.调用bean的init-method初始化方法

13.执行BeanPostProcessor的postProcessAfterInitialization

14.执行InstantiationAwareBeanPostProcessorAdapter的后置方法，postProcessAfterInitialization

15.Bean的使用

16.调用DiposibleBean的destory方法

17.调用bean指定的destory-method方法

用代码验证测试

测试Bean - StudentBean类：

/**
 * 测试生命周期的Bean
 */
public class StudentBean implements InitializingBean, DisposableBean, BeanNameAware, BeanFactoryAware {
    private String name;
    private int age;
 
    private String beanName;         //实现了BeanNameAware接口，Spring可以将BeanName注入该属性中
    private BeanFactory beanFactory; //实现了BeanFactory接口，Spring可将BeanFactory注入该属性中
 
 
    public StudentBean(){
        System.out.println("【Bean构造方法】学生类的无参构造方法");
    }
 
    @Override
    public String toString() {
        return "StudentBean{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", beanName='" + beanName + '\'' +
                '}';
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        System.out.println("【set注入】注入学生的name属性");
        this.name = name;
    }
 
    public int getAge() {
        return age;
    }
 
    public void setAge(int age) {
        System.out.println("【set注入】注入学生的age属性");
        this.age = age;
    }
 
    /**
     * 自己编写的初始化方法
     */
    public void myInit(){
        System.out.println("【init-method】调用init-method属性配置的初始化方法");
    }
 
    /**
     * 自己编写的销毁方法
     */
    public void myDestroy(){
        System.out.println("【destroy-method】调用destroy-method属性配置的销毁方法");
    }
 
    /**
     * BeanFactoryAware接口的方法
     * @param beanFactory
     * @throws BeansException
     */
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
        System.out.println("【BeanFactoryAware接口】调用BeanFactoryAware的setBeanFactory方法得到beanFactory引用");
    }
 
    /**
     * BeanNameAware接口的方法
     * @param name
     */
    public void setBeanName(String name) {
        this.beanName = name;
        System.out.println("【BeanNameAware接口】调用BeanNameAware的setBeanName方法得到Bean的名称");
    }
 
    /**
     * InitializingBean接口的方法
     * @throws Exception
     */
    public void afterPropertiesSet() throws Exception {
        System.out.println("【InitializingBean接口】调用InitializingBean接口的afterPropertiesSet方法");
    }
 
    /**
     * DisposableBean接口的方法
     * @throws Exception
     */
    public void destroy() throws Exception {
        System.out.println("【DisposableBean接口】调用DisposableBean接口的destroy方法");
    }
}

MyBeanFactoryPostProcessor工厂处理器类：

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
 
    public MyBeanFactoryPostProcessor() {
        System.out.println("【BeanFactoryPostProcessor接口】调用BeanFactoryPostProcessor实现类构造方法");
    }
 
    /**
     * 重写BeanFactoryPostProcessor接口的postProcessBeanFactory方法，可通过该方法对beanFactory进行设置
     */
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
            throws BeansException {
        System.out.println("【BeanFactoryPostProcessor接口】调用BeanFactoryPostProcessor接口的postProcessBeanFactory方法");
    }
}

MyInstantiationAwareBeanPostProcessor类：

/**
 * 一般情况下，当我们需要实现InstantiationAwareBeanPostProcessor接口时，是通过继承Spring框架中InstantiationAwareBeanPostProcessor接口实现类
 * InstantiationAwareBeanPostProcessorAdapter这个适配器类来简化我们实现接口的工作
 */
public class MyInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter {
 
    public MyInstantiationAwareBeanPostProcessor() {
        System.out.println("【InstantiationAwareBeanPostProcessor接口】调用InstantiationAwareBeanPostProcessor构造方法");
    }
 
    /**
     * 实例化Bean之前调用
    */
    public Object postProcessBeforeInstantiation(Class beanClass, String beanName) throws BeansException {
        System.out.println("【InstantiationAwareBeanPostProcessor接口】调用InstantiationAwareBeanPostProcessor接口的postProcessBeforeInstantiation方法");
        return null;
    }
 
    /**
     * 实例化Bean之后调用
     */
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("【InstantiationAwareBeanPostProcessor接口】调用InstantiationAwareBeanPostProcessor接口的postProcessAfterInitialization方法");
        return bean;
    }
 
    /**
     * 设置某个属性时调用
     */
    public PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName)
            throws BeansException {
        System.out.println("【InstantiationAwareBeanPostProcessor接口】调用InstantiationAwareBeanPostProcessor接口的postProcessPropertyValues方法");
        return pvs;
    }
}

MyBeanPostProcessor类：

public class MyBeanPostProcessor implements BeanPostProcessor {
 
    public MyBeanPostProcessor(){
        System.out.println("【BeanPostProcessor接口】调用BeanPostProcessor的构造方法");
    }
 
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("【BeanPostProcessor接口】调用postProcessBeforeInitialization方法，这里可对"+beanName+"的属性进行更改。");
        return bean;
    }
 
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("【BeanPostProcessor接口】调用postProcessAfterInitialization方法，这里可对"+beanName+"的属性进行更改。");
        return bean;
    }
}

XML配置：

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="
            http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">
    
    <!-- 生命周期测试  -->
    <!--配置Bean的后置处理器-->
    <bean id="beanPostProcessor" class="com.my.spring.life.MyBeanPostProcessor">
    </bean>
 
    <!--配置instantiationAwareBeanPostProcessor-->
    <bean id="instantiationAwareBeanPostProcessor" class="com.my.spring.life.MyInstantiationAwareBeanPostProcessor">
    </bean>
 
    <!--配置BeanFactory的后置处理器-->
    <bean id="beanFactoryPostProcessor" class="com.my.spring.life.MyBeanFactoryPostProcessor">
    </bean>
 
    <bean id="studentBean" class="com.my.spring.life.StudentBean" init-method="myInit"
          destroy-method="myDestroy" scope="singleton">
        <property name="name" value="yanxiao"></property>
        <property name="age" value="21"></property>
    </bean>
</beans>

测试类：

public class TestCyclelife {
 
    /*
     */
    public static void main(String[] args){
        System.out.println("--------------【初始化容器】---------------");
 
        ApplicationContext context = new ClassPathXmlApplicationContext("Springlife.xml");
        System.out.println("-------------------【容器初始化成功】------------------");
        //得到studentBean，并显示其信息
        StudentBean studentBean = context.getBean("studentBean",StudentBean.class);
        System.out.println(studentBean);
 
        System.out.println("--------------------【销毁容器】----------------------");
        ((ClassPathXmlApplicationContext)context).registerShutdownHook();
    }
}

测试结果如下：

结果

转载自:https://blog.csdn.net/weixin_40834464/article/details/82829999

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