Spring 源码之 invokeBeanFactoryPostProcessors
概述
invokeBeanFactoryPostProcessors 办法中次要是解决 BeanDefinitionRegistryPostProcessor 和 BeanFactoryPostProcessor，BeanDefinitionRegistryPostProcessor 是 BeanFactoryPostProcessor 的子接口，具备更弱小的性能。这两个接口是 Spring 再初始化前一个重要的扩大点。
invokeBeanFactoryPostProcessors 源码剖析
public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<String>();
// 判断 beanFactory 是否为 BeanDefinitionRegistry，beanFactory 为 DefaultListableBeanFactory,
// 而 DefaultListableBeanFactory 实现了 BeanDefinitionRegistry 接口，因而这边为 true
if (beanFactory instanceof BeanDefinitionRegistry) {BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// 用于寄存一般的 BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
// 用于寄存 BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
// 首先解决入参中的 beanFactoryPostProcessors
// 遍历所有的 beanFactoryPostProcessors, 将 BeanDefinitionRegistryPostProcessor 和一般 BeanFactoryPostProcessor 辨别开
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
// 如果是 BeanDefinitionRegistryPostProcessor
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// 间接执行 BeanDefinitionRegistryPostProcessor 接口的 postProcessBeanDefinitionRegistry 办法
registryProcessor.postProcessBeanDefinitionRegistry(registry); //@3
// 增加到 registryProcessors(用于最初执行 postProcessBeanFactory 办法)
registryProcessors.add(registryProcessor);
} else {
// 否则，只是一般的 BeanFactoryPostProcessor
// 增加到 regularPostProcessors(用于最初执行 postProcessBeanFactory 办法)
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.
// 用于保留本次要执行的 BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 调用所有实现 PriorityOrdered 接口的 BeanDefinitionRegistryPostProcessor 实现类
// 找出所有实现 BeanDefinitionRegistryPostProcessor 接口的 Bean 的 beanName
//@1
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
// 遍历 postProcessorNames
for (String ppName : postProcessorNames) {
// 校验是否实现了 PriorityOrdered 接口
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 获取 ppName 对应的 bean 实例, 增加到 currentRegistryProcessors 中,
// beanFactory.getBean: 这边 getBean 办法会触发创立 ppName 对应的 bean 对象, 目前暂不深刻解析
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
// 将要被执行的退出 processedBeans，防止后续反复执行
processedBeans.add(ppName);
}
}
// 进行排序(依据是否实现 PriorityOrdered、Ordered 接口和 order 值来排序)
sortPostProcessors(currentRegistryProcessors, beanFactory);
// 增加到 registryProcessors(用于最初执行 postProcessBeanFactory 办法)
registryProcessors.addAll(currentRegistryProcessors);
// 遍历 currentRegistryProcessors, 执行 postProcessBeanDefinitionRegistry 办法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// 执行结束后, 清空 currentRegistryProcessors
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// 调用所有实现了 Ordered 接口的 BeanDefinitionRegistryPostProcessor 实现类（过程跟下面的步骤 3 根本一样）// 找出所有实现 BeanDefinitionRegistryPostProcessor 接口的类, 这边反复查找是因为执行完下面的 BeanDefinitionRegistryPostProcessor,
// 可能会新增了其余的 BeanDefinitionRegistryPostProcessor, 因而须要从新查找
// @2
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 校验是否实现了 Ordered 接口，并且还未执行过
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);
// 遍历 currentRegistryProcessors, 执行 postProcessBeanDefinitionRegistry 办法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// 最初, 调用所有剩下的 BeanDefinitionRegistryPostProcessors
boolean reiterate = true;
while (reiterate) {
reiterate = false;
// 找出所有实现 BeanDefinitionRegistryPostProcessor 接口的类
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 跳过曾经执行过的
if (!processedBeans.contains(ppName)) {currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
// 如果有 BeanDefinitionRegistryPostProcessor 被执行, 则有可能会产生新的 BeanDefinitionRegistryPostProcessor,
// 因而这边将 reiterate 赋值为 true, 代表须要再循环查找一次
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 遍历 currentRegistryProcessors, 执行 postProcessBeanDefinitionRegistry 办法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 调用所有 BeanDefinitionRegistryPostProcessor 的 postProcessBeanFactory 办法(BeanDefinitionRegistryPostProcessor 继承自 BeanFactoryPostProcessor)
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// 最初, 调用入参 beanFactoryPostProcessors 中的一般 BeanFactoryPostProcessor 的 postProcessBeanFactory 办法
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
} else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// 到这里 , 入参 beanFactoryPostProcessors 和容器中的所有 BeanDefinitionRegistryPostProcessor 曾经全副处理完毕,
// 上面开始解决容器中的所有 BeanFactoryPostProcessor
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// 找出所有实现 BeanFactoryPostProcessor 接口的类
//@3
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 用于寄存实现了 PriorityOrdered 接口的 BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
// 用于寄存实现了 Ordered 接口的 BeanFactoryPostProcessor 的 beanName
List<String> orderedPostProcessorNames = new ArrayList<String>();
// 用于寄存一般 BeanFactoryPostProcessor 的 beanName
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
// 遍历 postProcessorNames, 将 BeanFactoryPostProcessor 按实现 PriorityOrdered、实现 Ordered 接口、一般三种辨别开
for (String ppName : postProcessorNames) {
// 跳过曾经执行过的
if (processedBeans.contains(ppName)) {// skip - already processed in first phase above} else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 增加实现了 PriorityOrdered 接口的 BeanFactoryPostProcessor
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
} else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
// 增加实现了 Ordered 接口的 BeanFactoryPostProcessor 的 beanName
orderedPostProcessorNames.add(ppName);
} else {
// 增加剩下的一般 BeanFactoryPostProcessor 的 beanName
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
// 调用所有实现 PriorityOrdered 接口的 BeanFactoryPostProcessor
// 对 priorityOrderedPostProcessors 排序
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
// 遍历 priorityOrderedPostProcessors, 执行 postProcessBeanFactory 办法
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
// 调用所有实现 Ordered 接口的 BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : orderedPostProcessorNames) {
// 获取 postProcessorName 对应的 bean 实例, 增加到 orderedPostProcessors, 筹备执行
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
// 对 orderedPostProcessors 排序
sortPostProcessors(orderedPostProcessors, beanFactory);
// 遍历 orderedPostProcessors, 执行 postProcessBeanFactory 办法
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
// 调用所有剩下的 BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
// 11.1 获取 postProcessorName 对应的 bean 实例, 增加到 nonOrderedPostProcessors, 筹备执行
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
// 遍历 nonOrderedPostProcessors, 执行 postProcessBeanFactory 办法
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
// 革除元数据缓存（mergedBeanDefinitions、allBeanNamesByType、singletonBeanNamesByType），// 因为后处理器可能曾经批改了原始元数据，例如，替换值中的占位符...
beanFactory.clearMetadataCache();}@1 这里会咱们能够看下 beanFactory 中只有 7 个 beanDefinition，其中只有 ConfigurationClassPostProcessor 是实现了 BeanDefinitionRegistryPostProcessor 接口
所以它会被优先执行。
ConfigurationClassPostProcessor 后置处理器是在 run()—>createApplicationContext()—>ApplicationContextFactory.create()—>
AnnotationConfigApplicationContext—->AnnotatedBeanDefinitionReader()—>
AnnotationConfigUtils.registerAnnotationConfigProcessors()增加的默认处理器。
@2 因为加载了 ConfigurationClassPostProcessor，零碎中可能新增一些实现了 BeanDefinitionRegistryPostProcessor 的类，对他们进行排序，遍历执行 postProcessBeanDefinitionRegistry 办法。
@3 加载所有实现了 BeanFactoryPostProcessor，执行 postProcessBeanFactory 办法
从代码执行的程序也能够晓得 BeanDefinitionRegistryPostProcessor 是在 BeanFactoryPostProcessor 之前执行
测试论证
@Component
public class BeanDefinitionRegistryPostProcessorOrder1 implements BeanDefinitionRegistryPostProcessor, Ordered {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {System.out.println("BeanDefinitionRegistryPostProcessorOrder1:::"+"postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("BeanDefinitionRegistryPostProcessorOrder1:::"+"postProcessBeanFactory");
}
@Override
public int getOrder() {return 1;}
}
@Component
public class BeanDefinitionRegistryPostProcessorOrder2 implements BeanDefinitionRegistryPostProcessor, Ordered {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("BeanDefinitionRegistryPostProcessorOrder2:::" + "postProcessBeanFactory");
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {System.out.println("BeanDefinitionRegistryPostProcessorOrder2:::" + "postProcessBeanDefinitionRegistry");
}
@Override
public int getOrder() {return 2;}
}
@Component
public class BeanFactoryPostProcessorOrder1 implements BeanFactoryPostProcessor, Ordered {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("BeanFactoryPostProcessorOrder1:::"+"postProcessBeanFactory");
}
@Override
public int getOrder() {return 1;}
}
@Component
public class BeanFactoryPostProcessorOrder2 implements BeanFactoryPostProcessor, Ordered {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("BeanFactoryPostProcessorOrder2:::" + "postProcessBeanFactory");
}
@Override
public int getOrder() {return 2;}
}
输入后果：BeanDefinitionRegistryPostProcessorOrder1:::postProcessBeanDefinitionRegistry
BeanDefinitionRegistryPostProcessorOrder2:::postProcessBeanDefinitionRegistry
BeanDefinitionRegistryPostProcessorOrder1:::postProcessBeanFactory
BeanDefinitionRegistryPostProcessorOrder2:::postProcessBeanFactory
BeanFactoryPostProcessorOrder1:::postProcessBeanFactory
BeanFactoryPostProcessorOrder2:::postProcessBeanFactory