1、源码解析
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
Set<String> processedBeans = new HashSet<>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
// 这里是拿到前面添加的 BeanFactoryPostProcessor
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
// 如果 BeanFactoryPostProcessor 是 BeanDefinitionRegistryPostProcessor 的话就调用它的 postProcessBeanDefinitionRegistry 方法。
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// 这里添加到 registryProcessors 中
registryProcessors.add(registryProcessor);
}
else {
// 这里添加到常规的 PostProcessors 中，BeanFactoryPostProcessor做了区分
regularPostProcessors.add(postProcessor);
}
}
// 下面就开始对 BeanDefinitionRegistryPostProcessor 开始按顺序执行了
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// 这里拿到所有的 BeanDefinitionRegistryPostProcessor 类型的 Bean 名称，@Component这些注解还没有被扫描进 IOC 中
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 这里判断 ppName 是否是 PriorityOrdered 或者是 PriorityOrdered 的子类
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
// 标记当前 Bean 已被处理
processedBeans.add(ppName);
}
}
// 这里对 BeanDefinitionRegistryPostProcessor 再排序,默认规则是根据 order
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 这里调用 BeanDefinitionRegistryPostProcessor 的 postProcessBeanDefinitionRegistry 方法。
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// 这边再获取 BeanDefinitionRegistryPostProcessor 类型的 Bean 名称，为什么这里还是要再获取而不用上面的呢，
// 考虑到上面调用的 postProcessBeanDefinitionRegistry 方法会注册进新的 BeanDefinitionRegistryPostProcessor
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 这里排除已被处理的 Bean 并且拿到实现了 Ordered 或者是子类的 BeanDefinitionRegistryPostProcessor
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
// 这里还是排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 调用 BeanDefinitionRegistryPostProcessor 的 postProcessBeanDefinitionRegistry 方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// 接下来就是处理上面新注册的 BeanDefinitionRegistryPostProcessor 了
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
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);
// 这里做这个标识是防止在 postProcessBeanDefinitionRegistry 中新注册了 BeanDefinitionRegistryPostProcessor 进来而没有被执行到。
// 所以说要循环处理
reiterate = true;
}
}
// 排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 调用 BeanDefinitionRegistryPostProcessor 的 postProcessBeanDefinitionRegistry 方法。
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 这里的话就调用 registryProcessors 的 postProcessBeanFactory 方法
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// 这里调用的是不是 BeanDefinitionRegistryPostProcessor 类型的 BeanFactoryPostProcessor 的 postProcessBeanFactory 方法。
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!
// 这边的话拿到所有的 BeanFactoryPostProcessor 类型 ,BeanDefinitionRegistryPostProcessor 的父类
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) {
// 跳过已被处理的.因为在后面也执行了 postProcessBeanFactory 可能会注册进 BeanFactoryPostProcessor,所以这里还有处理逻辑
//以下是排序操作
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);
}
}
//以下是按顺序执行 BeanFactoryPostProcessor 的 postProcessBeanFactory 方法.
// 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();
}
1.1、规则总结
以上总结来说就是：
会依次执行 BeanFactoryPostProcessor 与 BeanDefinitionRegistryPostProcessor 接口的相关方法。
如果是常规方法注册的，比如 @Component 注解注册那么会按照以下的顺序执行：
实现 PriorityOrdered 的 BeanDefinitionRegistryPostProcessor postProcessBeanDefinitionRegistry 方法先执行，order 越小越先执行；
实现 Ordered 的 BeanDefinitionRegistryPostProcessor postProcessBeanDefinitionRegistry 方法执行，order 越小越先执行；
未实现 PriorityOrdered 或者 Ordered 的 BeanDefinitionRegistryPostProcessor postProcessBeanDefinitionRegistry 方法执行，order 越小越先执行；
【1】
以上顺序的 postProcessBeanFactory 方法执行。
最后就是 BeanFactoryPostProcessor 的 postProcessBeanFactory 方法执行。
如果是使用 BeanDefinitionRegistryPostProcessor postProcessBeanDefinitionRegistry 方法注册的 BeanDefinitionRegistryPostProcessor 则遵循谁先注册谁先执行，执行顺序会插入到标记【1】的位置。
如果是使用 BeanDefinitionRegistryPostProcessor postProcessBeanFactory 注册的 BeanDefinitionRegistryPostProcessor，那么就有点特殊了，它的 postProcessBeanDefinitionRegistry 不会被执行，不知道是不
是一个 Spring 的一个 bug，看源码是因为通过未实现排序接口的 BeanDefinitionRegistryPostProcessor 的postProcessBeanFactory 方法注册的 BeanDefinitionRegistryPostProcessor 实现类，后面是没有执行 postProcessBeanDefinitionRegistry 方法的机会的。
如果以上看不明白，那么可以自己复制以下代码尝试一下：
@Component
public class Test1BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("我是Test1的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test1的postProcessBeanFactory");
}
@Override
public int getOrder() {
return 100;
}
}
@Component
public class Test1BeanFactoryPostProcessor implements BeanFactoryPostProcessor, PriorityOrdered {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test1BeanFactoryPostProcessor的postProcessBeanFactory");
}
@Override
public int getOrder() {
return 56;
}
}
@Component
public class Test2BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("我是Test2的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test2的postProcessBeanFactory");
}
@Override
public int getOrder() {
return 99;
}
}
@Component
public class Test3BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
registry.registerBeanDefinition("test9BeanDefinitionRegistryPostProcessor",new RootBeanDefinition(Test9BeanDefinitionRegistryPostProcessor.class));
System.out.println("我是Test3的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test3的postProcessBeanFactory");
beanFactory.registerSingleton("test6BeanDefinitionRegistryPostProcessor",new Test6BeanDefinitionRegistryPostProcessor());
}
@Override
public int getOrder() {
return 99;
}
}
@Component
public class Test4BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor{
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
registry.registerBeanDefinition("test5BeanDefinitionRegistryPostProcessor",new RootBeanDefinition(Test5BeanDefinitionRegistryPostProcessor.class));
System.out.println("我是Test4的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test4的postProcessBeanFactory");
beanFactory.registerSingleton("test7BeanDefinitionRegistryPostProcessor",new Test7BeanDefinitionRegistryPostProcessor());
}
}
public class Test5BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor , PriorityOrdered {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("我是Test5的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test5的postProcessBeanFactory");
}
@Override
public int getOrder() {
return 1;
}
}
public class Test6BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor{
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("我是Test6的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test6的postProcessBeanFactory");
}
}
public class Test7BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor{
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("我是Test7的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test7的postProcessBeanFactory");
}
}
@Component
public class Test8BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor, Ordered {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("我是Test8的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test8的postProcessBeanFactory");
}
@Override
public int getOrder() {
return 44;
}
}
public class Test9BeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("我是Test9的postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("我是Test9的postProcessBeanFactory");
}
}
最后再提一下一个特殊的 BeanDefinitionRegistryPostProcessor -> ConfigurationClassPostProcessor，它会处理项目中的 @Component、@Import 等这些注解然后将 BeanDefinition 加载到 IOC 当中的，当然了，后续再讲。
