BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor的区别

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BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor的区别

首先,这两个都是spring中的PostProcessor,并且BeanDefinitionRegistryPostProcessor是继承自BeanFactoryPostProcessor

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {

如果你了解spring源码和容器初始化过程,你就知道,上面的两种后置处理器都是对BeanDefinition进行一些处理,但是有一些功能上的E区别,这一点从源码中的注释就可以看出.

/**
 * Extension to the standard {@link BeanFactoryPostProcessor} SPI, allowing for
 * the registration of further bean definitions <i>before</i> regular
 * BeanFactoryPostProcessor detection kicks in. In particular,
 * BeanDefinitionRegistryPostProcessor may register further bean definitions
 * which in turn define BeanFactoryPostProcessor instances.
 *
 * @author Juergen Hoeller
 * @since 3.0.1
 * @see org.springframework.context.annotation.ConfigurationClassPostProcessor
 */
public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {

	/**
	 * Modify the application context's internal bean definition registry after its
	 * standard initialization. All regular bean definitions will have been loaded,
	 * but no beans will have been instantiated yet. This allows for adding further
	 * bean definitions before the next post-processing phase kicks in.
	 * @param registry the bean definition registry used by the application context
	 * @throws org.springframework.beans.BeansException in case of errors
	 */
	void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;

}

这里主要比较的就是BeanDefinitionRegistry接口和BeanFactoryPostProcessor中的ConfigurableListableBeanFactory接口,BeanDefinitionRegistry中多了一些操作beanDefinition的方法,比如向集合中添加一些自定义的beanDefinition,还可以删除beanDefinition,但是ConfigurableListableBeanFactory只能对其中的beanDefinition进行获取然后修改其中的属性.

所以在,注释中有这样一句话allowing for the registration of further bean definitions <i>before</i> regular BeanFactoryPostProcessor detection kicks in,也就是说,BeanDefinitionRegistryPostProcessor可以在执行BeanFactoryPostProcessor之前,向BeanDefinition容器中添加注册更多的BeanDefinition.

这里我画了一个简单的图示:

这里我写了一个简单的例子来证明这点:

/**
 * @author hi@54zh.cn 程序员大晖
 * @date 2021/11/7 - 11:07
 */
public class Student {

    String sname;

    public Student(String sname) {
        this.sname = sname;
    }

    public Student() {

    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    @Override
    public String toString() {
        return "Student{" +
                "sname='" + sname + '\'' +
                '}';
    }
}

/**
 * @author hi@54zh.cn 程序员大晖
 * @date 2021/11/7 - 11:08
 */
public class Teacher {

    String tname;

    public Teacher(String tname) {
        this.tname = tname;
    }

    public Teacher() {
    }

    public String getTname() {
        return tname;
    }

    public void setTname(String tname) {
        this.tname = tname;
    }

    @Override
    public String toString() {
        return "Teacher{" +
                "tname='" + tname + '\'' +
                '}';
    }
}

<?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 id="student"
          class="cn.zh54.bo.Student">
        <!--<property name="sname" value="zhangsan"/>-->
    </bean>
    <bean id="proces"
          class="cn.zh54.bo.MyBeanRegisterFactoryPostProcessor">
    </bean>
</beans>

/**
 * @author hi@54zh.cn 程序员大晖
 * @date 2021/11/7 - 15:19
 */
public class MyBeanRegisterFactoryPostProcessor implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        BeanDefinition studentBean = new GenericBeanDefinition();
        studentBean.setBeanClassName("cn.zh54.bo.Student");
        registry.registerBeanDefinition("student_real",studentBean);
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        BeanDefinition student = beanFactory.getBeanDefinition("student");
        student.setBeanClassName("cn.zh54.bo.Teacher");
    }
}

/**
 * @author hi@54zh.cn 程序员大晖
 * @date 2021/11/7 - 11:07
 */
public class Test {

    public final Teacher teacher = new Teacher();

    public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {

        ApplicationContext ioc =new ClassPathXmlApplicationContext("bean.xml");
        Teacher bean = (Teacher) ioc.getBean("student");
        Student bean1 = (Student) ioc.getBean("student_real");
        System.out.println(bean);
        System.out.println(bean1);
    }

}

开启spring源码范围的debug日志后结果如下:

16:57:00.874 [main] DEBUG org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loaded 2 bean definitions from class path resource [bean.xml]
16:57:00.896 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'proces'
16:57:00.916 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'student'
16:57:00.916 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'student_real'
Teacher{tname='null'}
Student{sname='null'}

实际上,在spring容器加载过程中,执行上述功能的就是下面的方法:

invokeBeanFactoryPostProcessors(beanFactory);

	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

		// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
		// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
		if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
		}
	}

这里在加载BeanDefinition的后置处理器时,需要注意按照spring中表示优先级的接口来保证加载的顺序,所以下面 也可以看到最先加载了实现了PriorityOrdered接口的处理器,之后加载实现了Ordered接口的处理器. 并且 先是获取BeanDefinitionRegistryPostProcessor的实现类,之后获取BeanFactoryPostProcessor的实现类.

public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

		// Invoke BeanDefinitionRegistryPostProcessors first, if any.
		Set<String> processedBeans = new HashSet<>();
        
		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
			//分别存放两种BeanDefinition的后置处理器
			List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
			List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					registryProcessors.add(registryProcessor);
				}
				else {
					regularPostProcessors.add(postProcessor);
				}
			}

			// Do not initialize FactoryBeans here: We need to leave all regular beans
			// uninitialized to let the bean factory post-processors apply to them!
			// Separate between BeanDefinitionRegistryPostProcessors that implement
			// PriorityOrdered, Ordered, and the rest.
			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
            
			// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					if (!processedBeans.contains(ppName)) {
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						processedBeans.add(ppName);
						reiterate = true;
					}
				}
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				currentRegistryProcessors.clear();
			}

			// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {
			// Invoke factory processors registered with the context instance.
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}

		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let the bean factory post-processors apply to them!
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			if (processedBeans.contains(ppName)) {
				// skip - already processed in first phase above
			}
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// Finally, invoke all other BeanFactoryPostProcessors.
		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
		for (String postProcessorName : nonOrderedPostProcessorNames) {
			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

		// Clear cached merged bean definitions since the post-processors might have
		// modified the original metadata, e.g. replacing placeholders in values...
		beanFactory.clearMetadataCache();
	}

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最后编辑时间为: 2021/11/07 17:48