spring篇：IOC容器加载过程源码探究（三）
承接上篇IOC容器加载过程源码探究（二）
继续分析refresh()方法：
postProcessBeanFactory(beanFactory)方法
// Allows post-processing of the bean factory in context subclasses.
// 子类来设置一下BeanFactory
postProcessBeanFactory(beanFactory);
这个方法是个空方法：
/**
* Modify the application context's internal bean factory after its standard
* initialization. All bean definitions will have been loaded, but no beans
* will have been instantiated yet. This allows for registering special
* BeanPostProcessors etc in certain ApplicationContext implementations.
* @param beanFactory the bean factory used by the application context
*/
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
}
留给子类去实现的，说到这个方法，插曲：这个接口BeanFactoryPostProcessor 中也有postProcessBeanFactory方法，咱们可以实现BeanFactoryPostProcessor接口中的这个postProcessBeanFactory方法，以后在分析扩展点时会重点讲。
invokeBeanFactoryPostProcessors(beanFactory)方法：
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory); // scanner.scan()
/**
* Instantiate and invoke all registered BeanFactoryPostProcessor beans,
* respecting explicit order if given.
* Must be called before singleton instantiation.
*/
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 重点研究
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)
// 关于LoadTimeWeaver看这篇文章了解即可，https://www.cnblogs.com/wade-luffy/p/6073702.html
if (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
先分析getBeanFactoryPostProcessors()
/** BeanFactoryPostProcessors to apply on refresh. */
private final List<BeanFactoryPostProcessor> beanFactoryPostProcessors = new ArrayList<>();
/**
* Return the list of BeanFactoryPostProcessors that will get applied
* to the internal BeanFactory.
*/
public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
return this.beanFactoryPostProcessors;
}
很显然，这个beanFactoryPostProcessors这是一个空集合，我们可以调用addBeanFactoryPostProcessor(BeanFactoryPostProcessor postProcessor)方法添加postProcessor。
@Override
public void addBeanFactoryPostProcessor(BeanFactoryPostProcessor postProcessor) {
Assert.notNull(postProcessor, "BeanFactoryPostProcessor must not be null");
this.beanFactoryPostProcessors.add(postProcessor);
}
addBeanFactoryPostProcessor(BeanFactoryPostProcessor postProcessor)这个方法就在AbstractApplicationContext中实现的，AnnotationConfigApplicationContext是AbstractApplicationContext的子类，因此我们可以直接annotationConfigApplicationContext.addBeanFactoryPostProcessor(XXX);
看一段关系图：
继续看invokeBeanFactoryPostProcessors方法，点开
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { // BeanFactoryPostProcessor、BeanDefinitionRegistryPostProcessor
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
// beanFactoryPostProcessors集合一般情况下都是空的，除非我们手动调用容器的addBeanFactoryPostProcessor方法添加了
// beanFactoryPostProcessors中可能包含了：普通BeanFactoryPostProcessor对象和BeanDefinitionRegistryPostProcessor对象
// 对于BeanDefinitionRegistryPostProcessor对象，会执行自己的postProcessBeanDefinitionRegistry()方法
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<>();
// 执行扫描出来的BeanDefinitionRegistryPostProcessor
// 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);
}
}
// 升序排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// processedBeans表示该beanFactoryPostProcessor的postProcessBeanDefinitionRegistry()方法已经执行过了，不再重复执行
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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// 执行哪些没有实现了PriorityOrdered或Ordered接口的普通BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
// 在这个过程中可能会向BeanFactory中注册另外的BeanDefinitionRegistryPostProcessor，所以需要while，直到确定所有的BeanDefinitionRegistryPostProcessor都执行完了
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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 执行完BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法后，
// 再执行BeanDefinitionRegistryPostProcessor的postProcessBeanFactory()方法
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// 执行手动添加的普通BeanFactoryPostProcessor的postProcessBeanFactory()方法
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// 执行扫描出来的普通BeanFactoryPostProcessor
// 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<>();
// 先进行分类
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();
}
要点分析：
BeanFactoryPostProcessors按入场方式分为：
* 1. 程序员调用ApplicationContext的API手动添加
* 2. Spring自己扫描出来的
BeanFactoryPostProcessor按类型又可以分为：
* 1. 普通BeanFactoryPostProcessor
* 2. BeanDefinitionRegistryPostProcessor
执行顺序顺序如下：
* 1. 执行手动添加的BeanDefinitionRegistryPostProcessor 的postProcessBeanDefinitionRegistry()方法
* 2. 执行扫描出来的BeanDefinitionRegistryPostProcessor（实现了PriorityOrdered）的postProcessBeanDefinitionRegistry()方法
* 3. 执行扫描出来的BeanDefinitionRegistryPostProcessor（实现了Ordered）的postProcessBeanDefinitionRegistry()方法
* 4. 执行扫描出来的BeanDefinitionRegistryPostProcessor（普通）的postProcessBeanDefinitionRegistry()方法
* 5. 执行扫描出来的BeanDefinitionRegistryPostProcessor（所有）的postProcessBeanFactory()方法
* 6. 执行手动添加的BeanFactoryPostProcessor的postProcessBeanFactory()方法
* 7. 执行扫描出来的BeanFactoryPostProcessor（实现了PriorityOrdered）的postProcessBeanFactory()方法
* 8. 执行扫描出来的BeanFactoryPostProcessor（实现了Ordered）的postProcessBeanFactory()方法
* 9. 执行扫描出来的BeanFactoryPostProcessor（普通）的postProcessBeanFactory()方法
本篇分析就到这里了，下面提几个问题：
1.beanFactory与FactoryBean的区别。
2.BeanFactoryPostProcessor在Spring中的用途。
3.StringIOC的加载过程。
4.Bean的生命周期。
5.Spring中有哪些扩展接口及调用时机。