Spring - BeanFactoryAware扩展接口

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Pre

Spring Boot - 扩展接口一览

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org.springframework.beans.factory.BeanFactoryAware

package org.springframework.beans.factory;

import org.springframework.beans.BeansException;

/**
 * Interface to be implemented by beans that wish to be aware of their
 * owning {@link BeanFactory}.
 *
 * 
For example, beans can look up collaborating beans via the factory
 * (Dependency Lookup). Note that most beans will choose to receive references
 * to collaborating beans via corresponding bean properties or constructor
 * arguments (Dependency Injection).
 *
 * 
For a list of all bean lifecycle methods, see the
 * {@link BeanFactory BeanFactory javadocs}.
 *
 * @author Rod Johnson
 * @author Chris Beams
 * @since 11.03.2003
 * @see BeanNameAware
 * @see BeanClassLoaderAware
 * @see InitializingBean
 * @see org.springframework.context.ApplicationContextAware
 */
public interface BeanFactoryAware extends Aware {

	/**
	 * Callback that supplies the owning factory to a bean instance.
	 * 
Invoked after the population of normal bean properties
	 * but before an initialization callback such as
	 * {@link InitializingBean#afterPropertiesSet()} or a custom init-method.
	 * @param beanFactory owning BeanFactory (never {@code null}).
	 * The bean can immediately call methods on the factory.
	 * @throws BeansException in case of initialization errors
	 * @see BeanInitializationException
	 */
	void setBeanFactory(BeanFactory beanFactory) throws BeansException;

}

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扩展点说明

扩展点方法为setBeanFactory，可以拿到BeanFactory这个属性。

使用场景：可以在bean实例化之后，但还未初始化之前，拿到 BeanFactory，在这个时候，可以对每个bean进行特殊化的定制。也或者可以把BeanFactory拿到进行缓存，日后使用。

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Aware接口

• Spring core 和 context的内建Aware接口

ApplicationEventPublisherAware
MessageSourceAware
ResourceLoaderAware
BeanFactoryAware
EnvironmentAware
EmbeddedValueResolverAware
ImportAware
LoadTimeWeaverAware
BeanClassLoaderAware
BeanNameAware
ApplicationContextAware

• Spring web内建的Aware接口

ServletContextAware
ServletConfigAware

• Spring其它内建Aware接口

SchedulerContextAware (spring scheduling)
NotificationPublisherAware (spring jmx export)
BootstrapContextAware (spring jca)

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Spring内建Aware接口的执行时机及顺序

Aware接口的执行时机肯定是在Spring Bean创建的时候。

对于Aware接口的执行实现主要有一下两种模式

• 初始化Bean（initializeBean）的时候直接进行方法调用 -> setXXXX
• BeanPostProcessor -> Object postProcessBeforeInitialization(Object bean, String beanName)

processor.postProcessBeforeInitialization(result, beanName);

进入到

Spring内置的核心Aware BeanPostProcessor是ApplicationContextAwareProcessor

org.springframework.context.support.ApplicationContextAwareProcessor#postProcessBeforeInitialization

我们继续看下 invokeAwareInterfaces(bean);

可知ApplicationContextAwareProcessor关联了大部分Spring内置Aware接口,它们的执行顺序如下：

EnvironmentAware -> EmbeddedValueResolverAware -> ResourceLoaderAware -> ApplicationEventPublisherAware -> MessageSourceAware ->   ApplicationStartupAware -> ApplicationContextAware

结论： 直接方法调用的时机要早于通过BeanPostProcessor#postProcessBeforeInitialization调用的时机

由于Aware的接口的调用受到BeanPostProcessor的直接影响，因此BeanPostProcessor的执行顺序也就是Aware接口的调用顺序。

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那刚才为啥直接跳到了 ApplicationContextAwareProcessor ？

我们看看可以看看ApplicationContextAwareProcessor的设置执行时机

AbstractApplicationContext#refresh方法

public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

      //....省略其余代码
}

继续看 prepareBeanFactory

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        //....省略其余代码
        // Configure the bean factory with context callbacks.
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));

      //....省略其余代码
}

可以看到 beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this)这里可以看到ApplicationContextAwareProcessor直接第一个加入到该BeanFactory中。

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源码解析 （直接调用）

org.springframework.context.support.PostProcessorRegistrationDelegate#registerBeanPostProcessors()
	BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		org.springframework.beans.factory.support.AbstractBeanFactory#getBean
		  org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean	
			  org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean
					org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean
						 

在 doCreateBean方法中

重点看

	// Initialize the bean instance.
		Object exposedObject = bean;
		try {
			populateBean(beanName, mbd, instanceWrapper);
			exposedObject = initializeBean(beanName, exposedObject, mbd);
		}

进入 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean

if (System.getSecurityManager() != null) {
			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
				invokeAwareMethods(beanName, bean);
				return null;
			}, getAccessControlContext());
		}
		else {
			invokeAwareMethods(beanName, bean);
		}

看

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#invokeAwareMethods

private void invokeAwareMethods(String beanName, 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);
			}
		}
	}

看到了吧

if (bean instanceof BeanFactoryAware) {
		((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}

由以上代码片段可以得出结论：Aware接口执行顺序是

 BeanNameAware -> BeanClassLoaderAware -> BeanFactoryAware

调用链如下

org.springframework.context.support.PostProcessorRegistrationDelegate#registerBeanPostProcessors()
	BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		org.springframework.beans.factory.support.AbstractBeanFactory#getBean
		  org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean	
			  org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean
					org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean
						 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean
								org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#invokeAwareMethods

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源码分析 （BeanPostProcessor调用执行顺序）

其实上面最开始的截图里已经有了，我们再看下

org.springframework.context.support.PostProcessorRegistrationDelegate#registerBeanPostProcessors()
	BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		org.springframework.beans.factory.support.AbstractBeanFactory#getBean
		  org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean	
			  org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean
					org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean
						 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean

继续 initializeBean 看

//....省略
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
  wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
 //....省略

@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;
}

public List<BeanPostProcessor> getBeanPostProcessors() {
  return this.beanPostProcessors;
}

private final List<BeanPostProcessor> beanPostProcessors = new CopyOnWriteArrayList<>();

可知beanPostProcessors是关联该BeanFactory的有序列表, 这个列表的数据来源就是ConfigurableBeanFactory#addBeanPostProcessor(BeanPostProcessor beanPostProcessor) 这个方法。

回到AbstractApplicationContext#refresh()中的

registerBeanPostProcessors(beanFactory);//向BeanFactory注入BeanPost

注册BeanPostProcessor的最终执行者是PostProcessorRegistrationDelegate.registerBeanPostProcessors

这其中的排序规则如下(针对于属于该BeanFactory的 BeanPostProcessor BeanDefinition):

String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

• 实现了PriorityOrdered接口优先级最高, 再按order进行排序 小 -> 大
• 其次是实现了Ordered接口, 再按order进行排序 小 -> 大
• 其它的根据BeanDefinition Spring注册顺序来

当然还可以通过BeanFactoryPostProcessor来配置该BeanFactory, 举个例子ConfigurationClassPostProcessor

@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
  int factoryId = System.identityHashCode(beanFactory);
  if (this.factoriesPostProcessed.contains(factoryId)) {
    throw new IllegalStateException(
      "postProcessBeanFactory already called on this post-processor against " + beanFactory);
  }
  this.factoriesPostProcessed.add(factoryId);
  if (!this.registriesPostProcessed.contains(factoryId)) {
    // BeanDefinitionRegistryPostProcessor hook apparently not supported...
    // Simply call processConfigurationClasses lazily at this point then.
    processConfigBeanDefinitions((BeanDefinitionRegistry) beanFactory);
  }

  enhanceConfigurationClasses(beanFactory);
  //注册添加ImportAware接口处理器
  beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));
}

private static class ImportAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter {

    ....

  @Override
  public Object postProcessBeforeInitialization(Object bean, String beanName) {
    if (bean instanceof ImportAware) {
      ImportRegistry ir = this.beanFactory.getBean(IMPORT_REGISTRY_BEAN_NAME, ImportRegistry.class);
      AnnotationMetadata importingClass = ir.getImportingClassFor(ClassUtils.getUserClass(bean).getName());
      if (importingClass != null) {
        //ImportAware#setImportMetadata调用
        ((ImportAware) bean).setImportMetadata(importingClass);
      }
    }
    return bean;
  }
}

由以上可知ImportAware执行顺序ApplicationContextAwareProcessor关联的那些Aware接口之后执行。

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其实还有一个 LoadTimeWeaverAwareProcessor

AbstractApplicationContext#prepareBeanFactory

// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {//有条件的注入, 必须存在该bean或者bean definition
  beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
  // Set a temporary ClassLoader for type matching.
  beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}

目前的Aware接口执行顺序如下：

BeanNameAware -> BeanClassLoaderAware -> BeanFactoryAware -> EnvironmentAware -> EmbeddedValueResolverAware -> ResourceLoaderAware -> ApplicationEventPublisherAware -> MessageSourceAware -> ApplicationContextAware -> ImportAware -> LoadTimeWeaverAware

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扩展点示例

package com.artisan.bootspringextend.testextends;

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.context.annotation.Configuration;

/**
 * @author 小工匠
 * @version 1.0
 * @description: TODO
 * @date 2022/12/4 9:53
 * @mark: show me the code , change the world
 */

@Slf4j
@Configuration
public class ExtendBeanFactoryAware implements BeanFactoryAware {
    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        log.info("----->ExtendBeanFactoryAware  {}" , beanFactory.getBean(ExtendBeanFactoryAware.class).getClass().getSimpleName());
    }
}
    

再看第二个比较全的扩展

 package com.artisan.bootspringextend.testextends;

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.context.*;
import org.springframework.context.annotation.ImportAware;
import org.springframework.context.weaving.LoadTimeWeaverAware;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.metrics.ApplicationStartup;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.instrument.classloading.LoadTimeWeaver;
import org.springframework.stereotype.Component;
import org.springframework.util.StringValueResolver;

/**
 * @author 小工匠
 * @version 1.0
 * @description: TODO
 * @date 2022/12/4 11:02
 * @mark: show me the code , change the world
 */
@Slf4j
@Component
public class ExtendInvokeAware implements BeanNameAware, BeanClassLoaderAware, BeanFactoryAware, EnvironmentAware, EmbeddedValueResolverAware,
        ResourceLoaderAware, ApplicationEventPublisherAware, MessageSourceAware,ApplicationStartupAware, ApplicationContextAware, ImportAware,
        LoadTimeWeaverAware {

    @Override
    public void setBeanClassLoader(ClassLoader classLoader) {
        log.info(" ------> BeanClassLoaderAware::setBeanClassLoader invoked");
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        log.info(" ------> BeanFactoryAware::setBeanFactory invoked");
    }

    @Override
    public void setBeanName(String s) {
        log.info(" ------> BeanNameAware::setBeanName invoked");
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        log.info(" ------> ApplicationContextAware::setApplicationContext invoked");
    }

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        log.info(" ------> ApplicationEventPublisherAware::setApplicationEventPublisher invoked");
    }

    @Override
    public void setEmbeddedValueResolver(StringValueResolver resolver) {
        log.info(" ------> EmbeddedValueResolverAware::setEmbeddedValueResolver invoked");
    }

    @Override
    public void setEnvironment(Environment environment) {
        log.info(" ------> EnvironmentAware::setEnvironment invoked");
    }

    @Override
    public void setMessageSource(MessageSource messageSource) {
        log.info(" ------> MessageSourceAware::setMessageSource invoked");
    }

    @Override
    public void setResourceLoader(ResourceLoader resourceLoader) {
        log.info(" ------> ResourceLoaderAware::setResourceLoader invoked");
    }

    @Override
    public void setApplicationStartup(ApplicationStartup applicationStartup) {
        log.info(" ------> ApplicationStartup::setApplicationStartup invoked");
    }

    @Override
    public void setImportMetadata(AnnotationMetadata importMetadata) {
        log.info(" ------> ImportAware::setImportMetadata invoked");
    }

    @Override
    public void setLoadTimeWeaver(LoadTimeWeaver loadTimeWeaver) {
        log.info(" ------> LoadTimeWeaverAware::setLoadTimeWeaver invoked");
    }


}

输出结果

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.4.2)

2022-12-04 19:14:25.103  INFO 12832 --- [           main] .b.t.ExtendApplicationContextInitializer : ExtendApplicationContextInitializer # initialize  Called
2022-12-04 19:14:25.110  INFO 12832 --- [           main] c.a.b.BootSpringExtendApplication        : Starting BootSpringExtendApplication using Java 1.8.0_261 on LAPTOP-JF3RBRRJ with PID 12832 (D:\IdeaProjects\boot2\boot-spring-extend\target\classes started by artisan in D:\IdeaProjects\boot2)
2022-12-04 19:14:25.111  INFO 12832 --- [           main] c.a.b.BootSpringExtendApplication        : No active profile set, falling back to default profiles: default
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> BeanNameAware::setBeanName invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> BeanClassLoaderAware::setBeanClassLoader invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> BeanFactoryAware::setBeanFactory invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> EnvironmentAware::setEnvironment invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> EmbeddedValueResolverAware::setEmbeddedValueResolver invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> ResourceLoaderAware::setResourceLoader invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> ApplicationEventPublisherAware::setApplicationEventPublisher invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> MessageSourceAware::setMessageSource invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> ApplicationStartup::setApplicationStartup invoked
2022-12-04 19:14:25.444  INFO 12832 --- [           main] c.a.b.testextends.ExtendInvokeAware      :  ------> ApplicationContextAware::setApplicationContext invoked
2022-12-04 19:14:25.529  INFO 12832 --- [           main] c.a.b.BootSpringExtendApplication        : Started BootSpringExtendApplication in 0.747 seconds (JVM running for 1.792)

Process finished with exit code 0