ApplicationContext刷新的时候上一步提到了，先调用BeanFactoryPostProcessors预处理下BeanFactory，现在注册Bean processors来拦截Bean的创建。
实例化，然后调用所有注册的BeanPostProcessor bean。如果指定了顺序，会按照顺序执行。
必须在应用Bean实例化之前调用。
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
分析
先看到还是这个工具类，在上步的BeanFactoryPostProcessors中使用的也是它。
image.png
注册BeanPostProcessor的代码如下：
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 获取BeanFactory中注册的类型为BeanPostProcessor.class的bean名称。一般获取到的是实现了BeanPostProcessor接口的Bean
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
// 注册一个BeanPostProcessorChecker，用来记录bean在BeanPostProcessor实例化时的信息。
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 将BeanPostProcessors分为实现了PriorityOrdered，Ordered等类型
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
// 如果BeanPostProcessors也实现了MergedBeanDefinitionPostProcessor接口，加入internalPostProcessors
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
// 首先注册实现了PriorityOrdered接口的BeanPostProcessors
sortPostProcessors(beanFactory, priorityOrderedPostProcessors);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
// 然后，注册实现了Ordered的BeanPostProcessors
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(beanFactory, orderedPostProcessors);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
// 现在注册所有常规的BeanPostProcessors
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
// 最后注册，所有的internal，也就是实现MergedBeanDefinitionPostProcessor的BeanPostProcessors
sortPostProcessors(beanFactory, internalPostProcessors);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
//添加ApplicationListenerDetector的BeanPostProcessor
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
整体代码也不难理解，如函数名，就是做了注册BeanPostProcessor
- 获取实现了BeanPostProcessor的bean Name，最开始Bean的信息注册到了beandifinitionMap中
- 将获取到的BeanPostProcessor分类，分为PriorityOrdered，Ordered和常规的类型
- 分别将PriorityOrdered，Ordered和常规的Bean添加进ApplicationContext的beanPostProcessors中，ApplicationContext的beanPostProcessors是ArrayList。
BeanFactory.getBeanNamesForType具体实现
其内部调用的是doGetBeanNamesForType
- 遍历beanDefinitionNames判断是否符合要求是否为type
- 遍历manualSingletonNames。
内部有个处理是如果Bean是FactoryBean，其名称前面加上&
private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit){
// Check all bean definitions.
// 检查所有的beanDefinitionNames。
for (String beanName : this.beanDefinitionNames) {
// Only consider bean as eligible if the bean name
// is not defined as alias for some other bean.
if (!isAlias(beanName)) {
try {
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
// Only check bean definition if it is complete.
if (!mbd.isAbstract() && (allowEagerInit ||
((mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading())) &&
!requiresEagerInitForType(mbd.getFactoryBeanName()))) {
// In case of FactoryBean, match object created by FactoryBean.
boolean isFactoryBean = isFactoryBean(beanName, mbd);
boolean matchFound = (allowEagerInit || !isFactoryBean || containsSingleton(beanName)) &&
(includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type);
if (!matchFound && isFactoryBean) {
// In case of FactoryBean, try to match FactoryBean instance itself next.
beanName = FACTORY_BEAN_PREFIX + beanName;
matchFound = (includeNonSingletons || mbd.isSingleton()) && isTypeMatch(beanName, type);
}
if (matchFound) {
result.add(beanName);
}
}
}
....
}
// Check manually registered singletons too.
for (String beanName : this.manualSingletonNames) {
try {
// In case of FactoryBean, match object created by FactoryBean.
if (isFactoryBean(beanName)) {
if ((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)) {
result.add(beanName);
// Match found for this bean: do not match FactoryBean itself anymore.
continue;
}
// In case of FactoryBean, try to match FactoryBean itself next.
beanName = FACTORY_BEAN_PREFIX + beanName;
}
// Match raw bean instance (might be raw FactoryBean).
if (isTypeMatch(beanName, type)) {
result.add(beanName);
}
}
...
}
return StringUtils.toStringArray(result);
}
TODO
- BeanFactory中beanDefinitionNames，manualSingletonNames等属性深入理解
最后
注册BeanPostProcessor和invokeBeanFactoryPostProcessors很像，并且没什么复杂逻辑。就是将已经注册到beanFacory的Bean筛选出BeanPostProcessor然后添加到ApplicationContext的beanPostProcessor集合中。
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