Spring Bean的生命周期

2023-11-25 12:55:04

转自：https://www.cnblogs.com/zrtqsk/p/3735273.html。

Spring Bean生命周期流程图

Spring Bean的完整生命周期从创建Spring容器开始，直到最终Spring容器销毁Bean，这其中包含了一系列关键点。

Spring Bean的生命周期

Spring Bean的生命周期

若容器注册了以上各种接口，程序那么将会按照以上的流程进行。下面将仔细讲解各接口作用。

各种接口方法分类

Bean的完整生命周期经历了各种方法调用，这些方法可以划分为以下几类：

  • Bean自身的方法: 这个包括了Bean本身调用的方法和通过配置文件中<bean>的init-method和destroy-method指定的方法。
  • Bean级生命周期接口方法: 这个包括了BeanNameAware、BeanFactoryAware、InitializingBean和DiposableBean这些接口的方法。
  • 容器级生命周期接口方法: 这个包括了InstantiationAwareBeanPostProcessor和BeanPostProcessor这两个接口实现，一般称它们的实现类为"后处理器"。
  • 工厂后处理器接口方法: 这个包括了AspectJWeavingEnabler, ConfigurationClassPostProcessor, CustomAutowireConfigurer等等非常有用的工厂后处理器接口的方法。工厂后处理器也是容器级的。在应用上下文装配配置文件之后立即调用。

演示

我们用一个简单的Spring Bean来演示一下Spring Bean的生命周期。

1. 首先是一个简单的Spring Bean，调用Bean自身的方法和Bean级生命周期接口方法，为了方便演示，它实现了BeanNameAware、BeanFactoryAware、InitializingBean和DisposableBean这4个接口，同时有2个方法，对应配置文件中<bean>的init-method和destroy-method。如下：

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

/**
 * Demo Spring Bean
 */
@Slf4j
public class Person implements BeanFactoryAware, BeanNameAware,
        InitializingBean, DisposableBean {

    private String name;
    private String address;
    private int phone;

    private BeanFactory beanFactory;
    private String beanName;

    public Person() {
        if (log.isInfoEnabled()) {
            log.info("【构造器】调用Person的构造器实例化");
        }
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        if (log.isInfoEnabled()) {
            log.info("【注入属性】注入属性name");
        }
        this.name = name;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        if (log.isInfoEnabled()) {
            log.info("【注入属性】注入属性address");
        }
        this.address = address;
    }

    public int getPhone() {
        return phone;
    }

    public void setPhone(int phone) {
        if (log.isInfoEnabled()) {
            log.info("【注入属性】注入属性phone");
        }
        this.phone = phone;
    }

    @Override
    public String toString() {
        return "Person [address=" + address + ", name=" + name + ", phone="
                + phone + "]";
    }

    /**
     * 这是BeanFactoryAware接口方法
     *
     * @param arg0
     * @throws BeansException
     */
    @Override
    public void setBeanFactory(BeanFactory arg0) throws BeansException {
        if (log.isInfoEnabled()) {
            log.info("【BeanFactoryAware接口】调用BeanFactoryAware.setBeanFactory()");
        }
        this.beanFactory = arg0;
    }

    /**
     * 这是BeanNameAware接口方法
     *
     * @param arg0
     */
    @Override
    public void setBeanName(String arg0) {
        if (log.isInfoEnabled()) {
            log.info("【BeanNameAware接口】调用BeanNameAware.setBeanName()");
        }
        this.beanName = arg0;
    }

    /**
     * 这是InitializingBean接口方法
     *
     * @throws Exception
     */
    @Override
    public void afterPropertiesSet() throws Exception {
        if (log.isInfoEnabled()) {
            log.info("【InitializingBean接口】调用InitializingBean.afterPropertiesSet()");
        }
    }

    /**
     * 这是DisposableBean接口方法
     *
     * @throws Exception
     */
    @Override
    public void destroy() throws Exception {
        if (log.isInfoEnabled()) {
            log.info("【DisposableBean接口】调用DisposableBean.destroy()");
        }
    }

    /**
     * 通过<bean>的init-method属性指定的初始化方法
     */
    public void myInit() {
        if (log.isInfoEnabled()) {
            log.info("【init-method】调用<bean>的init-method属性指定的初始化方法");
        }
    }

    /**
     * 通过<bean>的destroy-method属性指定的初始化方法
     */
    public void myDestroy() {
        if (log.isInfoEnabled()) {
            log.info("【destroy-method】调用<bean>的destroy-method属性指定的初始化方法");
        }
    }
}

2. 接下来是BeanPostProcessor接口的方法：

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

@Slf4j
public class MyBeanPostProcessor implements BeanPostProcessor {

    public MyBeanPostProcessor() {
        super();
        if (log.isInfoEnabled()) {
            log.info("这是BeanPostProcessor实现类构造器！！");
        }
    }

    @Override
    public Object postProcessAfterInitialization(Object arg0, String arg1)
            throws BeansException {
        if (log.isInfoEnabled()) {
            log.info("BeanPostProcessor接口方法postProcessAfterInitialization对属性进行更改！");
        }
        return arg0;
    }

    @Override
    public Object postProcessBeforeInitialization(Object arg0, String arg1)
            throws BeansException {
        if (log.isInfoEnabled()) {
            log.info("BeanPostProcessor接口方法postProcessBeforeInitialization对属性进行更改！");
        }
        return arg0;
    }
}

如上，BeanPostProcessor接口包括2个方法postProcessAfterInitialization和postProcessBeforeInitialization，这两个方法的第一个参数都是要处理的Bean对象，第二个参数都是Bean的name。返回值也都是要处理的Bean对象。这里要注意。

3. InstantiationAwareBeanPostProcessor 接口本质是BeanPostProcessor的子接口，一般我们继承Spring为其提供的适配器类InstantiationAwareBeanPostProcessor Adapter来使用它，如下：

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter;

import java.beans.PropertyDescriptor;

@Slf4j
public class MyInstantiationAwareBeanPostProcessor extends
        InstantiationAwareBeanPostProcessorAdapter {

    public MyInstantiationAwareBeanPostProcessor() {
        super();
        if (log.isInfoEnabled()) {
            log.info("这是InstantiationAwareBeanPostProcessorAdapter实现类构造器！！");
        }
    }

    // 接口方法、实例化Bean之前调用
    @Override
    public Object postProcessBeforeInstantiation(Class beanClass,
                                                 String beanName) throws BeansException {
        if (log.isInfoEnabled()) {
            log.info("InstantiationAwareBeanPostProcessor调用postProcessBeforeInstantiation方法");
        }
        return null;
    }

    // 接口方法、实例化Bean之后调用
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
        if (log.isInfoEnabled()) {
            log.info("InstantiationAwareBeanPostProcessor调用postProcessAfterInitialization方法");
        }
        return bean;
    }

    // 接口方法、设置某个属性时调用
    @Override
    public PropertyValues postProcessPropertyValues(PropertyValues pvs,
                                                    PropertyDescriptor[] pds, Object bean, String beanName)
            throws BeansException {
        if (log.isInfoEnabled()) {
            log.info("InstantiationAwareBeanPostProcessor调用postProcessPropertyValues方法");
        }
        return pvs;
    }
}

这个有3个方法，其中第二个方法postProcessAfterInitialization就是重写了BeanPostProcessor的方法。第三个方法postProcessPropertyValues用来操作属性，返回值也应该是PropertyValues对象。

4. 工厂后处理器接口方法：

import lombok.extern.slf4j.Slf4j;
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;

@Slf4j
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {

    public MyBeanFactoryPostProcessor() {
        super();
        if (log.isInfoEnabled()) {
            log.info("这是BeanFactoryPostProcessor实现类构造器！！");
        }
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory arg0)
            throws BeansException {
        if (log.isInfoEnabled()) {
            log.info("BeanFactoryPostProcessor调用postProcessBeanFactory方法");
        }
        BeanDefinition bd = arg0.getBeanDefinition("person");
        bd.getPropertyValues().addPropertyValue("phone", "110");
    }

}

5. Spring配置文件：

<?xml version="1.0" encoding="UTF-8"?>

<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">

    <bean id="beanPostProcessor" class="com.huawei.nlz.springplayground.lifecycle.xmlconfig.MyBeanPostProcessor">
    </bean>

    <bean id="instantiationAwareBeanPostProcessor"
          class="com.huawei.nlz.springplayground.lifecycle.xmlconfig.MyInstantiationAwareBeanPostProcessor">
    </bean>

    <bean id="beanFactoryPostProcessor"
          class="com.huawei.nlz.springplayground.lifecycle.xmlconfig.MyBeanFactoryPostProcessor">
    </bean>

    <bean id="person" class="com.huawei.nlz.springplayground.lifecycle.xmlconfig.Person" init-method="myInit"
          destroy-method="myDestroy" scope="singleton" p:name="张三" p:address="广州"
          p:phone="15900000000"/>

</beans>

6. 测试代码：

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

@Slf4j
public class Main {

    public static void main(String[] args) {
        if (log.isInfoEnabled()) {
            log.info("现在开始初始化容器");
        }

        ApplicationContext factory = new ClassPathXmlApplicationContext("com/huawei/nlz/springplayground/lifecycle/xmlconfig/applicationContext.xml");
        if (log.isInfoEnabled()) {
            log.info("容器初始化成功");
        }
        Person person = factory.getBean("person", Person.class);
        if (log.isInfoEnabled()) {
            log.info("Person是: {}", String.valueOf(person));
        }

        if (log.isInfoEnabled()) {
            log.info("现在开始关闭容器！");
        }
        ((ClassPathXmlApplicationContext) factory).registerShutdownHook();
    }

}

7. 输出如下：

16:57:39.845 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Main - 现在开始初始化容器
16:57:40.277 [main] INFO  c.h.n.s.l.x.MyBeanFactoryPostProcessor - 这是BeanFactoryPostProcessor实现类构造器！！
16:57:40.296 [main] INFO  c.h.n.s.l.x.MyBeanFactoryPostProcessor - BeanFactoryPostProcessor调用postProcessBeanFactory方法
16:57:40.299 [main] INFO  c.h.n.s.l.x.MyBeanPostProcessor - 这是BeanPostProcessor实现类构造器！！
16:57:40.300 [main] INFO  c.h.n.s.l.x.MyInstantiationAwareBeanPostProcessor - 这是InstantiationAwareBeanPostProcessorAdapter实现类构造器！！
16:57:40.305 [main] INFO  c.h.n.s.l.x.MyInstantiationAwareBeanPostProcessor - InstantiationAwareBeanPostProcessor调用postProcessBeforeInstantiation方法
16:57:40.305 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【构造器】调用Person的构造器实例化
16:57:40.353 [main] INFO  c.h.n.s.l.x.MyInstantiationAwareBeanPostProcessor - InstantiationAwareBeanPostProcessor调用postProcessPropertyValues方法
16:57:40.377 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【注入属性】注入属性address
16:57:40.377 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【注入属性】注入属性name
16:57:40.377 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【注入属性】注入属性phone
16:57:40.377 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【BeanNameAware接口】调用BeanNameAware.setBeanName()
16:57:40.377 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【BeanFactoryAware接口】调用BeanFactoryAware.setBeanFactory()
16:57:40.377 [main] INFO  c.h.n.s.l.x.MyBeanPostProcessor - BeanPostProcessor接口方法postProcessBeforeInitialization对属性进行更改！
16:57:40.377 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【InitializingBean接口】调用InitializingBean.afterPropertiesSet()
16:57:40.377 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【init-method】调用<bean>的init-method属性指定的初始化方法
16:57:40.377 [main] INFO  c.h.n.s.l.x.MyBeanPostProcessor - BeanPostProcessor接口方法postProcessAfterInitialization对属性进行更改！
16:57:40.377 [main] INFO  c.h.n.s.l.x.MyInstantiationAwareBeanPostProcessor - InstantiationAwareBeanPostProcessor调用postProcessAfterInitialization方法
16:57:40.391 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Main - 容器初始化成功
16:57:40.391 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Main - Person是: Person [address=广州, name=张三, phone=110]
16:57:40.393 [main] INFO  c.h.n.s.lifecycle.xmlconfig.Main - 现在开始关闭容器！
16:57:40.396 [Thread-0] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【DisposableBean接口】调用DisposableBean.destroy()
16:57:40.396 [Thread-0] INFO  c.h.n.s.lifecycle.xmlconfig.Person - 【destroy-method】调用<bean>的destroy-method属性指定的初始化方法

Process finished with exit code 0

 

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