spring的核心方法只之invokeBeanFactoryPostProcessors

invokeBeanFactoryPostProcessors就是将项目中的BeanDefinition加载进beanDefinitionMap中，并且对BeanFactoryPostProcess的实现类进行回调的地方。

先往spring容器中加入四个扩展类，便于下面演示。

HandFactoryPostProcessor: 手动的往spring容器中加入的BeanFactoryPostProcessor的实现类

public class HandFactoryPostProcessor implements BeanFactoryPostProcessor {
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		System.out.println("HandFactoryPostProcessor ---> postProcessBeanFactory");
	}
}

HandRegisterPostProcessor：手动的往spring容器中加入的BeanDefinitionRegistryPostProcessor的实现类

public class HandRegisterPostProcessor implements BeanDefinitionRegistryPostProcessor {
	@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
		System.out.println("HandRegisterPostProcessor ---> postProcessBeanDefinitionRegistry");
	}

	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		System.out.println("HandRegisterPostProcessor ---> postProcessBeanFactory");
	}
}

ScanFactoryPostProcessor：通过注解的方式往spring容器中加入的BeanFactoryPostProcessor的实现类

@Component
public class ScanFactoryPostProcessor implements BeanFactoryPostProcessor {
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		System.out.println("ScanFactoryPostProcessor ---> postProcessBeanFactory");
	}
}

ScanRegisterPostProcessor：通过注解的方式往spring容器中加入的BeanDefinitionRegistryPostProcessor的实现类

@Component
public class ScanRegisterPostProcessor implements BeanDefinitionRegistryPostProcessor {
	@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
		System.out.println("ScanRegisterPostProcessor ---> postProcessBeanDefinitionRegistry");
	}

	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		System.out.println("ScanRegisterPostProcessor ---> postProcessBeanFactory");
	}
}

这里说的程序员手动加入是指，在执行spring容器的refresh方法之前就，通过调用容器的接口，手动的往容器中加入BeanDefinitionRegistryPostProcessor接口的实现类的做法，代码如下。

AnnotationConfigApplicationContext ioc = new AnnotationConfigApplicationContext();
// 手动加入HandFactoryPostProcessor和HandRegisterPostProcessor
ioc.addBeanFactoryPostProcessor(new HandFactoryPostProcessor());
ioc.addBeanFactoryPostProcessor(new HandRegisterPostProcessor());
ioc.register(AppConfig.class);
ioc.refresh();

invokeBeanFactoryPostProcessors方法的执行主要包括一下几个部分：

执行程序员手动加入到容器中的BeanDefinitionRegistryPostProcessor接口的实现类。

源码如下：

for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
    if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
        BeanDefinitionRegistryPostProcessor registryProcessor =
            (BeanDefinitionRegistryPostProcessor) postProcessor;
        // 此处即为执行手动加入到容器中的BeanDefinitionRegistryPostProcessor接口的实现类。
        registryProcessor.postProcessBeanDefinitionRegistry(registry);
        registryProcessors.add(registryProcessor);
    }
    else {
        // 只实现BeanFactoryPostProcessor接口的扩展接口
        regularPostProcessors.add(postProcessor);
    }
}

运行完上述源码的控制台结果如下：

执行了通过手动方式加入到容器中的BeanDefinitionRegistryPostProcessor接口的实现类

调用实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor的扩展类

ps：在这一步所执行的扩展类可以是spring自带的扩展类或是程序员往程序中加入的，平时主要是执行spring自带的扩展类比如ConfigurationClassPostProcessor：用于解析往spring容器中注入BeanDefinition的注解@Configuration, @Bean, @Service, @Component, @Repository, @Import等。

源代码如下：

// 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);
// 为了之后可以不用再去找父类，因为现在实现完BeanDefinitionRegistryPostProcessor中的方法之后，后面还需要用到这个扩展类
registryProcessors.addAll(currentRegistryProcessors);
/**
 * 执行实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor的扩展类
 */
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();

运行到此阶段执行的BeanDefinitionRegistryPostProcessor扩展类如下：

调用实现了Ordered接口的BeanDefinitionRegistryPostProcessor的扩展类。

源码如下：

// 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();

执行逻辑与调用实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor的扩展类类似。

调用没有实现PriorityOrdered和Ordered接口BeanDefinitionRegistryPostProcessor的扩展类。（这一步执行完之后BeanDefinitionRegistryPostProcessor的扩展类都执行完了）

源码如下：

// 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)) {
            // 找到剩下来的那些还没有被执行过的BeanDefinitionRegistryPostProcessor
            currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
            processedBeans.add(ppName);
            reiterate = true;
        }
    }
    sortPostProcessors(currentRegistryProcessors, beanFactory);
    registryProcessors.addAll(currentRegistryProcessors);
    // 到此为止所有的BeanDefinitionRegistryPostProcessor中的扩展口都被执行过了
    invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
    currentRegistryProcessors.clear();
}

这里调用的BeanDefinitionRegistryPostProcessor接口的实现类如下：

执行结果：

调用BeanDefinitionRegistryPostProcessor的父类方法（因为BeanDefinitionRegistryPostProcessor接口也是继承了BeanFactoryPostProcessor接口，所以BeanDefinitionRegistryPostProcessor的父类方法就是指的扩展类中的postProcessBeanFactory方法）

源码如下：
```
// registryProcessors 为 List<BeanDefinitionRegistryPostProcessor>，是之前调用的所有的BeanDefinitionRegistryPostProcessor接口的实现类。
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
```
执行结果是：

调用程序员手动加入到容器中的BeanFactoryPostProcessors的扩展类。

源码如下：

// regularPostProcessors，为先前手动加入到spring容器中的BeanFactoryPostProcessors接口的实现类
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);

执行结果：

调用实现了PriorityOrdered接口的BeanFactoryPostProcessors的扩展类。

源码如下：

// 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);

和上述执行实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor的扩展类逻辑一致。

调用实现了Ordered接口的BeanFactoryPostProcessors的扩展类。

源码如下：

		// 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);

调用没有实现PriorityOrdered和Ordered接口的BeanFactoryPostProcessors的扩展类。

源码如下：

// 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);

执行结果：

spring的核心方法只之invokeBeanFactoryPostProcessors

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