在beanFactory准备好之后，(配置ignoreDependecy,ResolvableDependency,PostProcessors)，现在要调用BeanFactoryPostProcessors了。
实例化然后调用所有注册的BeanFactoryPostProcessor Bean。必须在单例(singleton)实例化之前调用。
可以看到这个方法使用的是PostProcessorRegistrationDelegate的静态方法，getBeanFactoryPostProcessors()，获取的是BeanFactoryPostProcessors，默认为空，如果需要我们可以在postProcessBeanFactory方法中指定，因为这个方法默认也是没有实现的。
这里也可以发现：ApplicationContext是对beanFactory的封装，其内部包含了对beanFactory的前置处理还有多种附加功能。
而BeanFactory针对的是Bean的处理。
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
}
分析
这里面的一段代码实在是有点长，分开一部分一部分的看。
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<String>();
// beanFactory默认使用的是DefaultListableBeanFactory，因此是BeanDefinitionRegistry的实例
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
//准备两种PostProcessors
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
List<BeanDefinitionRegistryPostProcessor> registryPostProcessors =
new LinkedList<BeanDefinitionRegistryPostProcessor>();
//将传进来的beanFactoryPostProcessors分成两种类型，如果是BeanDefinitionRegistryPostProcessor类型的还会进行postProcess一下，其它类型的先添加进regularPostProcessors列表中
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryPostProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryPostProcessor.postProcessBeanDefinitionRegistry(registry);
registryPostProcessors.add(registryPostProcessor);
}
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.
// 先不要实例化FactoryBeans，我们需要等到bean被factory post-processors处理。
//分类BeanDefinitionRegistryPostProcessors, 按照实现PriorityOrdered，Ordered等分类。
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
List<BeanDefinitionRegistryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
// 排序，普通的集合排序，然后安装顺序调用BeanDefinitionRegistryPostProcessor
sortPostProcessors(beanFactory, priorityOrderedPostProcessors);
registryPostProcessors.addAll(priorityOrderedPostProcessors);
invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry);
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// 处理实现Ordered的BeanDefinitionRegistryPostProcessor
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
List<BeanDefinitionRegistryPostProcessor> orderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(beanFactory, orderedPostProcessors);
registryPostProcessors.addAll(orderedPostProcessors);
invokeBeanDefinitionRegistryPostProcessors(orderedPostProcessors, registry);
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
//处理不被processedBeans包含的Bean
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
BeanDefinitionRegistryPostProcessor pp = beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class);
registryPostProcessors.add(pp);
processedBeans.add(ppName);
pp.postProcessBeanDefinitionRegistry(registry);
reiterate = true;
}
}
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 所有的目前处理的processors，调用postProcessBeanFactory的回调
invokeBeanFactoryPostProcessors(registryPostProcessors, 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!
//不要初始化FactoryBeans，我们需要让Bean factory post-processors处理普通的bean。
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
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(beanFactory, priorityOrderedPostProcessors);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(beanFactory, orderedPostProcessors);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
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();
}
代码看起来很长，不过大部分的代码处理逻辑类似，细看的话不复杂。
主要是
- beanFactoryPostProcessors分成BeanDefinitionRegistryPostProcessor与regularPostProcessors。BeanDefinitionRegistryPostProcessor在划分的时候也会调用下postProcessBeanDefinitionRegistry(registry)
- BeanDefinitionRegistryPostProcessor分成实现了PriorityOrdered，Ordered还有其他的统一处理，分类之后调用postProcessBeanDefinitionRegistry(registry)方法
- BeanFactoryPostProcessor分成实现PriorityOrdered，Ordered等接口的类型，然后统一调用postProcessBeanFactory方法
- 清空cache
默认情况下，ApplicationContext中的beanFactoryPostProcessors是需要我们自定义的，这需要我们对beanFactoryPostProcessors有较深的理解，后面可以研究下beanFactoryPostProcessors
TODO
- beanFactoryPostProcessors用法，demo
最后
这次一起看了invokeBeanFactoryPostProcessors方法，这是实例化Factory之前预处理部分，更深的理解还要坚持看下去理解。
