invokeBeanFactoryPostProcessors方法會實例化所有BeanFactoryPostProcessor以及其子類BeanDefinitionRegistryPostProcessor。這兩個類主要針對的是BeanFactory的，其作用是在BeanDefinition創建之後，Bean 實例化對象前對BeanDefinition對象相關屬性進行修改；另外還有一個類叫BeanPostProcessor，該類主要針對的是 Bean 操作的。關於這兩個類的區別我會在下一篇內容介紹。
1. 在講AbstractApplicationContext.refresh()的invokeBeanFactoryPostProcessors開始之前。在講之前先簡單說下爲啥沒有講prepareBeanFactory和postProcessBeanFactory兩個方法，因爲這兩個方法都特別簡單，第一個方法是爲BeanFactory設置各種各樣的屬性，包括一些BeanPostProcessor的設置（BeanPostProcessor後面會專門講解）等等，第二個方法沒有具體實現，是爲開發者留出擴展的。
AbstractApplicationContext.invokeBeanFactoryPostProcessors()方法實現
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 獲取context中已添加的beanFactoryPostProcessors
// 實例化並調用所有BeanFactoryPostProcessors
// 主要實現也是在該方法裏面進行實現
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()));
}
}
2. 該方法的主要實現在invokeBeanFactoryPostProcessors方法裏面進行實現的。（雖然這個方法特別長，但是邏輯很簡單，耐心看下去）
BeanFactoryPostProcessor：一切處理BeanFactory的父接口BeanDefinitionRegistryPostProcessor：實現了BeanFactoryPostProcessor接口的接口
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors()方法實現
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
// Step1：beanFactory是BeanDefinitionRegistry接口或者是其子類
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// Step2：存放普通的beanFactoryPostProcessors
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<>();
// Step3：存放beanDefinitionRegistryPostProcessors
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<>();
// Step4：首先處理接口傳進來的factoryPostProcessors
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
// Step5：實現了BeanDefinitionRegistryPostProcessor接口的factoryPostProcessor
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// Step6：直接調用其實現
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// Step7：添加到registryProcessors裏面，後面調用 BeanFactoryPostProcessor.postProcessBeanFactory()方法
registryProcessors.add(registryProcessor);
}
else {
// Step8：非BeanFactoryProcessor及其子類的，直接添加到regularPostProcessors裏面，後面調用執行postProcessorBeanFactory方法
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.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// Step9：獲取所有BeanDefinitionRegistryPostProcessor實現的子類並且實現了PriorityOrdered接口的factoryPostProcessor
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);
}
}
// Step10：排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
// Step11：添加到registryProcessors中，後面調用postProcessorBeanFactory方法
registryProcessors.addAll(currentRegistryProcessors);
// Step12：遍歷執行每個factoryPostProcessor的postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// Step13：清空
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// Step14：獲取所有BeanDefinitionRegistryPostProcessor並且實現了Ordered接口的factoryPostProcessor
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);
}
}
// Step15：排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
// Step16：添加到registryProcessors中，後面調用postProcessorBeanFactory方法
registryProcessors.addAll(currentRegistryProcessors);
// Step17：遍歷每個factoryPostProcessor的postProcessorBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// Step18：清空
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// Step19：獲取所有實現了BeanDefinitionRegistryPostProcessor接口的類，且沒有實現PriorityOrdered接口和Ordered接口的類
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;
}
}
// Step20：排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
// Step21：添加到registryProcessors中，後面調用PostProcessorBeanFactory方法
registryProcessors.addAll(currentRegistryProcessors);
// Step22：遍歷每個factoryPostProcessor的PostProcessorBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// Step23：所有實現了BeanDefinitionRegistryPostProcessor接口的類，調用beanFactoryPostProcessors方法
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// Step24：所有實現了BeanFactoryPostProcessor接口的類，調用BeanFactoryPostProcessor方法
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
// Step26：所有非BeanDefinitionRegistry接口及其子類的工廠，直接調用BeanFactoryPostProcessor方法
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!
// Step27：獲取所有實現了BeanFactoryPostProcessor接口的類名
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) {
// Step28：跳過已經invoke的factoryPostProcessor
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
// Step29：實現了BeanFactoryPostProcessor接口並且實現了PriorityOrdered接口的類
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
// Step30：實現了BeanFactoryPostProcessor並且實現了Ordered接口的類
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
// Step31：普通的BeanFactoryPostProcessor類
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
// Step32：排序
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Step33：調用BeanFactoryPostProcessor方法
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
// Step34：實現了Ordered接口排序並調用BeanFactoryPostProcessor方法
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
// Step35：普通的BeanFactoryPostProcessor調用beanFactoryPostProcessor方法
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
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();
}
總結
先加載預先在上線文中定義的
BeanFactoryPostProcessor然後加載實現了
BeanDefinitionRegistryPostProcessor接口的BeanFactoryPostProcessor然後加載實現了
BeanFactoryPostProcessor接口的類在 Spring 和 mybatis 整合中，
MapperScannerConfigurer.java就實現了BeanDefinitionRegistryPostProcessor接口，在其實現的方法postProcessorBeanDefinitionRegistry中，掃描basePackage指定的路徑，將該目錄下的類封裝成BeanDefinition 並加載到BeanFactory中。所以項目中的接口不需要配置在 XML 文件中或者用註解聲明，而可以直接使用 Dao 類對應的實例化對象。再比如PropertySourcesPlaceholderConfigurer（實現了context:property-placeholder的功能），主要作用是替換掉 ${} 佔位符的內容，其重寫了postProcessorBeanFactory方法
講完invokeBeanFactoryPostProcessors相關實現後，下一篇我們來看看registerBeanPostProcessors都實現了些什麼功能，它和本篇文章將的invokeBeanFactoryPostProcessors方法有什麼區別。
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