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Spring-bean的生命周期-终篇

news 2025/7/2 21:46:35
阶段8：Bean属性设置阶段

属性设置阶段分为3个小的阶段

  • 实例化后阶段
  • Bean属性赋值前处理
  • Bean属性赋值

实例化后阶段
这里也有spring给我们预留了扩展，就是实现InstantiationAwareBeanPostProcessor的postProcessAfterInstantiation方法，开发者实现这个接口，重写此方法可以了
源码：

for (BeanPostProcessor bp : getBeanPostProcessors()) {if (bp instanceof InstantiationAwareBeanPostProcessor) {InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {return;}}
}

postProcessAfterInstantiation 方法返回false的时候，后续的Bean属性赋值前处理、Bean属性赋值都会被跳过了。

spring源码位置：

default boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {return true;
}

来个案例，先建一个process

/*** @description: 设置赋值前，如果返回false将不会被赋值** 会调用 InstantiationAwareBeanPostProcessor 接口的 postProcessAfterInstantiation 这个方* 法，调用逻辑如下：，* 后续的Bean属性赋值前处理、Bean* 属性赋值都会被跳过了。* @author: stone* @date: Created by 2021/3/25 20:25* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.setprop*/
public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor {/*** 后续的Bean属性赋值前处理、Bean*  属性赋值都会被跳过了。* @param bean* @param beanName* @return* @throws BeansException*/@Overridepublic boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
//        System.out.println("调用 MyInstantiationAwareBeanPostProcessor#postProcessAfterInstantiation");if ("pig1".equalsIgnoreCase(beanName)) {return false;}return true;}

再来一个spring bean

package com.shiguiwu.springmybatis.spring.lifecycle.definition;import com.shiguiwu.springmybatis.spring.lifecycle.instance.MyAutowire;
import lombok.Data;/*** @description: 小猪* @author: stone* @date: Created by 2021/3/17 14:08* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.definition*/
@Data
public class Pig {private String name;private Integer age;private String description;public Pig() {}@MyAutowirepublic Pig(String name, Integer age) {System.out.println("增强候选注解@MyAutowire ！！！！");this.name = name;this.age = age;}public Pig(String name, Integer age, String description) {this.name = name;this.age = age;this.description = description;}
}

测试案例如下：

public class InstancedTests {public static void main(String[] args) {DefaultListableBeanFactory factory = new DefaultListableBeanFactory();factory.addBeanPostProcessor(new MyInstantiationAwareBeanPostProcessor());BeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(Pig.class).addPropertyValue("name", "猪八戒").addPropertyValue("age", 30).getBeanDefinition();BeanDefinition beanDefinition1 = BeanDefinitionBuilder.genericBeanDefinition(Pig.class).addPropertyValue("name", "猪悟能").addPropertyValue("age", 35).getBeanDefinition();factory.registerBeanDefinition("pig", beanDefinition);factory.registerBeanDefinition("pig1", beanDefinition1);Arrays.stream(factory.getBeanDefinitionNames()).forEach(s -> System.out.println(factory.getBean(s)));}
}

打印结果

Connected to the target VM, address: '127.0.0.1:52046', transport: 'socket'
20:22:20.387 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'pig'
调用InstantiationAwareBeanPostProcessor #postProcessProperties
Pig(name=猪无能, age=12, description=null)
20:22:20.770 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'pig1'
Pig(name=null, age=null, description=null)
Disconnected from the target VM, address: '127.0.0.1:52046', transport: 'socket'

被指定的bean名称，跳过了属性赋值

Bean属性赋值前阶段
这个阶段，spring照样为开发者预留了干涉spring bean赋值前阶段的操作，这个阶段会调用 InstantiationAwareBeanPostProcessor 接口的postProcessProperties 方法，调
用逻辑：
代码如下：

for (BeanPostProcessor bp : getBeanPostProcessors()) {if (bp instanceof InstantiationAwareBeanPostProcessor) {InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);if (pvsToUse == null) {if (filteredPds == null) {filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);}pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds,bw.getWrappedInstance(), beanName);if (pvsToUse == null) {return;}}pvs = pvsToUse;}
}

从上面可以看出，如果 InstantiationAwareBeanPostProcessor 中的
postProcessProperties 和 postProcessPropertyValues 都返回空的时候，表示这个bean不
需要设置属性，直接返回了，直接进入下一个阶段。

来看一下 postProcessProperties 这个方法的定义：

@Nullable
default PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {return pvs;
}

PropertyValues中保存了bean实例对象中所有属性值的设置，所以我们可以在这个这个方法中对PropertyValues值进行修改

示例代码如下：

@Override
public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) throws BeansException {System.out.println("调用InstantiationAwareBeanPostProcessor #postProcessProperties");if (beanName.equals("pig")) {if (pvs==null) {pvs = new MutablePropertyValues();}if (pvs instanceof MutablePropertyValues) {MutablePropertyValues pv = (MutablePropertyValues) pvs;//偷梁换柱，给属性辅助pv.add("name", "猪无能");pv.add("age", 12);}}return null;
}

Bean属性赋值阶段
这个过程比较简单了，循环处理 PropertyValues 中的属性值信息，通过反射调用set方法将属性的值设置到bean实例中。
PropertyValues中的值是通过bean xml中property元素配置的，或者调用MutablePropertyValues中add方法设置的值。

阶段9：Bean初始化阶段

这个阶段分为5个小的阶段

  • Bean Aware接口回调
  • Bean初始化前操作
  • Bean初始化操作
  • Bean初始化后操作
  • Bean初始化完成操作

Bean Aware接口回调,这里也是spring给我们的扩展
这块的源码：

private void invokeAwareMethods(final String beanName, final Object bean) {if (bean instanceof Aware) {if (bean instanceof BeanNameAware) {((BeanNameAware) bean).setBeanName(beanName);}if (bean instanceof BeanClassLoaderAware) {ClassLoader bcl = getBeanClassLoader();if (bcl != null) {((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);}}if (bean instanceof BeanFactoryAware) {((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);}}
}

如果我们的bean实例实现了上面的接口，会按照下面的顺序依次进行调用：

BeanNameAware：将bean的名称注入进去
BeanClassLoaderAware：将BeanClassLoader注入进去
BeanFactoryAware：将BeanFactory注入进去

来一个实现这三个接口的类：

/*** @description: 三个接口* @author: stone* @date: Created by 2021/3/28 11:54* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.init*/
public class MyAware implements BeanNameAware, BeanClassLoaderAware, BeanFactoryAware {@Overridepublic void setBeanName(String name) {System.out.println("beanName:" + name);}@Overridepublic void setBeanClassLoader(ClassLoader classLoader) {System.out.println("classLoader:" + classLoader);}@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {System.out.println("beanFactory:" + beanFactory);}
}

测试代码：

package com.shiguiwu.springmybatis.spring.lifecycle.init;import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;/*** @description: 9.1初始化-aware接口回调* @author: stone* @date: Created by 2021/3/28 11:51* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.init*/
public class AwareTests {public static void main(String[] args) {DefaultListableBeanFactory factory = new DefaultListableBeanFactory();BeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(MyAware.class).getBeanDefinition();factory.registerBeanDefinition("myAware", beanDefinition);System.out.println(factory.getBean(MyAware.class));}
}

输出信息

Connected to the target VM, address: '127.0.0.1:55707', transport: 'socket'
22:21:14.221 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'myAware'
beanName:myAware
classLoader:sun.misc.Launcher$AppClassLoader@18b4aac2
beanFactory:org.springframework.beans.factory.support.DefaultListableBeanFactory@6c3f5566: defining beans [myAware]; root of factory hierarchy
com.shiguiwu.springmybatis.spring.lifecycle.init.MyAware@71248c21
Disconnected from the target VM, address: '127.0.0.1:55707', transport: 'socket'

Bean初始化前操作，spring给开发者的扩展
这个阶段的源码：

@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName) throws BeansException {Object result = existingBean;for (BeanPostProcessor processor : getBeanPostProcessors()) {Object current = processor.postProcessBeforeInitialization(result, beanName);if (current == null) {return result;}result = current;}return result;
}

会调用 BeanPostProcessor的postProcessBeforeInitialization 方法，若返回null，当前方法将结束。
通常称postProcessBeforeInitialization这个方法为：bean初始化前操作。
这个接口有2个实现类，比较重要,画重点：

org.springframework.context.support.ApplicationContextAwareProcessor
org.springframework.context.annotation.CommonAnnotationBeanPostProcessor

ApplicationContextAwareProcessor注入6个Aware接口对象
如果bean实现了下面的接口，在ApplicationContextAwareProcessor#postProcessBeforeInitialization 中会依次调用下面接口中的方法，将 Aware 前缀对应的对象注入到bean实例中。

EnvironmentAware：注入Environment对象
EmbeddedValueResolverAware：注入EmbeddedValueResolver对象
ResourceLoaderAware：注入ResourceLoader对象
ApplicationEventPublisherAware：注入ApplicationEventPublisher对象
MessageSourceAware：注入MessageSource对象
ApplicationContextAware：注入ApplicationContext对象

从名称上可以看出这个类以 ApplicationContext 开头的，说明这个类只能在 ApplicationContext 环境中使用。

CommonAnnotationBeanPostProcessor调用@PostConstruct标注的方法
CommonAnnotationBeanPostProcessor#postProcessBeforeInitialization 中会调用bean中所有标注@PostConstruct注解的方法
整体来个案例

package com.shiguiwu.springmybatis.spring.lifecycle.init;import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.context.EmbeddedValueResolverAware;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.MessageSource;
import org.springframework.context.MessageSourceAware;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ResourceLoader;
import org.springframework.util.StringValueResolver;import javax.annotation.PostConstruct;/*** @description: 初始化前操作* @author: stone* @date: Created by 2021/3/28 12:06* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.init*/
public class BeforeBean implements EnvironmentAware, EmbeddedValueResolverAware,ResourceLoaderAware, ApplicationEventPublisherAware, MessageSourceAware,ApplicationContextAware {@PostConstructpublic void postConstruct1() {System.out.println("postConstruct1");}@PostConstructpublic void postConstruct2() {System.out.println("postConstruct2");}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {System.out.println("applicationContext：" + applicationContext);}@Overridepublic void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {System.out.println("applicationEventPublisher：" + applicationEventPublisher);}@Overridepublic void setEmbeddedValueResolver(StringValueResolver resolver) {System.out.println("resolver：" + resolver);}@Overridepublic void setEnvironment(Environment environment) {System.out.println("environment：" + environment);}@Overridepublic void setMessageSource(MessageSource messageSource) {System.out.println("messageSource：" + messageSource);}@Overridepublic void setResourceLoader(ResourceLoader resourceLoader) {System.out.println("resourceLoader：" + resourceLoader);}
}

测试代码如下：

package com.shiguiwu.springmybatis.spring.lifecycle.init;import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;/*** @description: 9.2初始化前* @author: stone* @date: Created by 2021/3/28 12:04* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.init*/
public class BeforeInitTests {public static void main(String[] args) {AnnotationConfigApplicationContext factory = new AnnotationConfigApplicationContext();
//        BeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(BeforeBean.class).getBeanDefinition();
//        factory.("beforeBean", beanDefinition);factory.register(BeforeBean.class);factory.refresh();System.out.println(factory.getBean(BeforeBean.class));}
}

打印结果

environment：StandardEnvironment {activeProfiles=[], defaultProfiles= ...
resolver：org.springframework.beans.factory.config.EmbeddedValueResolver@3a52dba3
resourceLoader：org.springframework.context.annotation.AnnotationConfigApplicationContext@11438d26, started on Tue Nov 02 22:59:30 CST 2021
applicationEventPublisher：org.springframework.context.annotation.AnnotationConfigApplicationContext@11438d26, started on Tue Nov 02 22:59:30 CST 2021
messageSource：org.springframework.context.annotation.AnnotationConfigApplicationContext@11438d26, started on Tue Nov 02 22:59:30 CST 2021
applicationContext：org.springframework.context.annotation.AnnotationConfigApplicationContext@11438d26, started on Tue Nov 02 22:59:30 CST 2021
postConstruct1
postConstruct2
com.shiguiwu.springmybatis.spring.lifecycle.init.BeforeBean@610f7aa

大家可以去看一下AnnotationConfigApplicationContext的源码，其内部会添加很多
BeanPostProcessor 到 DefaultListableBeanFactory 中。

Bean初始化阶段
2个步骤

  1. 调用InitializingBean接口的afterPropertiesSet方法
  2. 调用定义bean的时候指定的初始化方法
    调用InitializingBean接口的afterPropertiesSet方法
public interface InitializingBean {public void afterPropertiesSet() throws Exception;
}

当我们的bean实现了这个接口的时候，会在这个阶段被调用
调用bean定义的时候指定的初始化方法
方式1：xml方式指定初始化方法

<bean init-method="bean中方法名称"/>

方式2：@Bean的方式指定初始化方法

@Bean(initMethod = "初始化的方法")

方式3：api的方式指定初始化方法

this.beanDefinition.setInitMethodName(methodName);

初始化方法最终会赋值给下面这个字段

org.springframework.beans.factory.support.AbstractBeanDefinition#initMethodName

案例如下：

package com.shiguiwu.springmybatis.spring.lifecycle.init;import org.springframework.beans.factory.InitializingBean;/*** @description: 初始化bean* @author: stone* @date: Created by 2021/3/28 13:04* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.init*/
public class InitializeBean implements InitializingBean {public void init() {System.out.println("初始化方法！！！！");}@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("afterPropertiesSet");}
}

测试代码

package com.shiguiwu.springmybatis.spring.lifecycle.init;import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;/*** @description: 9.3初始化阶段* @author: stone* @date: Created by 2021/3/28 13:02* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.init*/
public class InitializeTests {public static void main(String[] args) {DefaultListableBeanFactory factory = new DefaultListableBeanFactory();BeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(InitializeBean.class).getBeanDefinition();beanDefinition.setInitMethodName("init");factory.registerBeanDefinition("initializeBean", beanDefinition);System.out.println(factory.getBean(InitializeBean.class));}
}

输出结果

23:09:16.350 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory 
afterPropertiesSet
初始化方法！！！！
com.shiguiwu.springmybatis.spring.lifecycle.init.InitializeBean@221af3c0
'socket'

调用顺序：InitializingBean中的afterPropertiesSet、然后在调用自定义的初始化方法

Bean初始化后阶段

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName) throws BeansException {Object result = existingBean;Object current;for(Iterator iterator = this.getBeanPostProcessors().iterator(); iterator.hasNext(); result = current) {BeanPostProcessor processor = (BeanPostProcessor)iterator.next();current = processor.postProcessAfterInitialization(result, beanName);if (current == null) {return result;}}return result;
}

调用 BeanPostProcessor接口的postProcessAfterInitialization方法 ，返回null的时候，会中断上面的操作,注意这里也是扩展哦
通常称postProcessAfterInitialization这个方法为：bean初始化后置操作。
来个案例

public class MyBeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {System.out.println("bean :" + beanName);System.out.println("初始化后》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》");return bean;}
}

测试代码

package com.shiguiwu.springmybatis.spring.lifecycle.init;import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;/*** @description: 9.4初始化后阶段* @author: stone* @date: Created by 2021/3/28 13:07* @version: 1.0.0* @pakeage: com.shiguiwu.springmybatis.spring.lifecycle.init*/
public class AfterInitializeTests {public static void main(String[] args) {DefaultListableBeanFactory factory = new DefaultListableBeanFactory();//叫一个初始化后处理器factory.addBeanPostProcessor(new MyBeanPostProcessor());AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(String.class).addConstructorArgValue( "shiguiwu").getBeanDefinition();AbstractBeanDefinition beanDefinition1 = BeanDefinitionBuilder.genericBeanDefinition(Integer.class).addConstructorArgValue(15).getBeanDefinition();factory.registerBeanDefinition("shiguiwuabc", beanDefinition);factory.registerBeanDefinition("shiguiwuA", beanDefinition1);System.out.println(factory.getBean(String.class));System.out.println(factory.getBean(Integer.class));}
}

输出结果

Connected to the target VM, address: '127.0.0.1:56910', transport: 'socket'
23:20:37.770 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'shiguiwuabc'
bean :shiguiwuabc
初始化后》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》
shiguiwu
23:20:38.099 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'shiguiwuA'
bean :shiguiwuA
初始化后》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》
15
Disconnected from the target VM, address: '127.0.0.1:56910', transport: 'socket'Process finished with exit code 0

此致，终篇完毕，内容有点，希望能好好消化，接下来就是尾篇。

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