Spring源码解析之BeanPostProcessor
作者：互联网
前言
AbstractApplicationContext类
refresh()方法
spring在bean的注册与实例化之间会出现如下代码
//bean的注册
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
//1. Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
//2. Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
//3. Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
//bean的实例化
finishBeanFactoryInitialization(beanFactory);1.在AbstractApplicationContext为一个空方法，其子类对该方法进行了重写
2.BeanDefinitionRegistryPostProcessor与BeanFactoryPostProcessor接口的调用
3.把实现了BeanPostProcessor接口的类实例化，并且加入到BeanFactory中
invokeBeanFactoryPostProcessors()的源码分析
看个例子
BeanDefinitionTest类
@Component
public class BeanDefinitionTest implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
GenericBeanDefinition genericBeanDefinition = new GenericBeanDefinition();
genericBeanDefinition.setBeanClass(BeanClass.class);
MutablePropertyValues propertyValues = genericBeanDefinition.getPropertyValues();
propertyValues.addPropertyValue("username", "蔡徐坤");
beanDefinitionRegistry.registerBeanDefinition("beanClass", genericBeanDefinition);
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
BeanClass beanClass = (BeanClass) configurableListableBeanFactory.getBean("beanClass");
System.out.println("postProcessBeanFactory="+beanClass.getUsername());
}
}BeanClass类
@Data
public class BeanClass {
private String username;
}测试方法
@Test
public void test5() {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext("cn.com.dq");
BeanClass beanClass = (BeanClass) applicationContext.getBean("beanClass");
System.out.println(beanClass.getUsername());
}结果输出
从上述例子我们来看invokeBeanFactoryPostProcessors()的源码
PostProcessorRegistrationDelegate类
invokeBeanFactoryPostProcessors()方法
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// 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<>();
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<>();
//获取实现了BeanDefinitionRegistryPostProcessor接口的所有类的BeanDefinition对象的beanName
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
//判断是否实现了排序接口 PriorityOrdered
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
//排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
//调用过程
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
//判断是否是实现的Ordered接口
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);
currentRegistryProcessors.clear();
//没实现排序接口的调用
// 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);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
//
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
//调用postProcessBeanFactory方法
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
//获取实现了BeanFactoryPostProcessor接口的类，获取beanDefinition的名称
// 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<>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
//实现了PriorityOrdered接口的
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
//实现了Ordered接口的
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
//没实现接口的
nonOrderedPostProcessorNames.add(ppName);
}
}
//排序
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
//调用
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
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.
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();
}上述代码执行过程：
1.获取所有实现BeanDefinitionRegistryPostProcessor接口的beanName
2.注意这行代码
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));我们知道beanFactory.getBean()是bean的实例化，这里是优先将实现BeanDefinitionRegistryPostProcessor接口的bean进行实例化，然后加入到currentRegistryProcessors容器中
3.接下来执行了这行代码
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
}我们可以看到最终是执行了BeanDefinitionRegistryPostProcessor 接口的postProcessBeanDefinitionRegistry方法
4.我们回过来看我们写的demo类
我们在postProcessBeanDefinitionRegistry方法中重新注册了一个我们新创建的bean叫做beanClass，并且给beanClass里的属性赋值了蔡徐坤
5.执行完所有的有关BeanDefinitionRegistryPostProcessor 接口的postProcessBeanDefinitionRegistry方法调用后
接着调用了如下代码
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
private static void invokeBeanFactoryPostProcessors(
Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {
for (BeanFactoryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanFactory(beanFactory);
}
}从上面可以看出 是执行了BeanDefinitionRegistryPostProcessor 接口的postProcessBeanFactory方法
BeanDefinitionRegistryPostProcessor接口继承了BeanFactoryPostProcessor接口，postProcessBeanFactory方法为
BeanFactoryPostProcessor中的方法
6.回到demo
我们在这个方法中通过getBean操作实例化了beanClass然后打印了该实例中的属性，因此能解释我们写的demo控制台的输出
7.通过与BeanDefinitionRegistryPostProcessor 相同的方式，处理了实现BeanFactoryPostProcessor接口的bean的postProcessBeanFactory方法的调用
registerBeanPostProcessors方法的源码分析
PostProcessorRegistrationDelegate类
registerBeanPostProcessors方法
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
//拿到工程里面所有实现了BeanPostProcessor接口的类，获取到BeanDefinition的名称
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.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
//提前实例化BeanPostProcessor类型的bean，然后bean进行排序
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
//getBean是实例化方法，后面我们在讲bean实例化过程
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
//判断类型是否是MergedBeanDefinitionPostProcessor，如果是则代码是内部使用的
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.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
//注册到BeanFactory中
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
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.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}1.拿到工程里面所有实现了BeanPostProcessor接口的类，获取到BeanDefinition的名称
2.遍历所有的beanName,在循环中，我们看到一个比较重要的代码
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);我们知道beanFactory.getBean()是bean的实例化，所以，我们可以得到spring容器在实例化bean的时候，优先实例化的是BeanPostProcessor类型的bean，为什么要优先实例化BeanPostProcessor类型的bean，因为其他bean的实例化需要调用BeanPostProcessor里面的方法
3.实例化BeanPostProcessor类型的bean以后，接下来会将这些bean注册到beanFactory的beanPostProcessors容器中
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
private static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
for (BeanPostProcessor postProcessor : postProcessors) {
beanFactory.addBeanPostProcessor(postProcessor);
}
}
AbstractBeanFactory类
public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
// Remove from old position, if any
this.beanPostProcessors.remove(beanPostProcessor);
// Track whether it is instantiation/destruction aware
if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
this.hasInstantiationAwareBeanPostProcessors = true;
}
if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
this.hasDestructionAwareBeanPostProcessors = true;
}
// Add to end of list
this.beanPostProcessors.add(beanPostProcessor);
}这里有一个比较有意思的变量hasInstantiationAwareBeanPostProcessors ，在bean实例化的时候，会利用到这个变量
在bean实例化的时候会解释这个变量的作用
总结
1.invokeBeanFactoryPostProcessors方法首先是对实现了BeanDefinitionRegistryPostProcessor接口的bean进行了实例化，接着对BeanDefinitionRegistryPostProcessor中的postProcessBeanDefinitionRegistry方法进行了调用，然后对BeanDefinitionRegistryPostProcessor中的 postProcessBeanFactory方法进行了调用
2.invokeBeanFactoryPostProcessors 接下来对实现了BeanFactoryPostProcessor接口的bean进行了实例化，然后对BeanFactoryPostProcessor中的postProcessBeanFactory方法进行了调用
3.registerBeanPostProcessors()提前对所有实现了BeanPostProcessor 接口的bean进行实例化，然后将这些bean注册到beanFactory的beanPostProcessors容器中
4.spring在bean的实例化过程中，优先实例化的是实现了BeanDefinitionRegistryPostProcessor的bean，其次是实现了
BeanFactoryPostProcessor接口的bean，再次是实现了BeanPostProcessor 接口的bean，最后是普通bean
标签：BeanPostProcessor,beanFactory,Spring,ppName,add,bean,源码,BeanDefinitionRegistryPo 来源： https://www.cnblogs.com/honeylemon/p/16226890.html