Spring源码-11-后置处理器ConfigurationClassPostProcessor
Bean工厂后置处理器
一 类图
二 Demo
// MyTest00.java
public class MyTest00 {
public static void main(String[] args) {
DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
beanFactory.registerBeanDefinition("myCfg00", new RootBeanDefinition(MyCfg00.class));
ConfigurationClassPostProcessor postProcessor = new ConfigurationClassPostProcessor();
postProcessor.postProcessBeanDefinitionRegistry(beanFactory);
}
}
// MyCfg00.java
@Configuration
public class MyCfg00 {
}
三 BeanDefinitionRegistryPostProcessor抽象回调
// ConfigurationClassPostProcessor.java
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
int registryId = System.identityHashCode(registry);
if (this.registriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
}
if (this.factoriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanFactory already called on this post-processor against " + registry);
}
this.registriesPostProcessed.add(registryId);
this.processConfigBeanDefinitions(registry);
}
// ConfigurationClassPostProcessor.java
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
/**
* 把配置类缓存起来
* 配置类区分为
* - full型
* - @Configuration注解的proxyBeanMethods属性是true
* - lite型
* - @Configuration注解的proxyBeanMethods属性是false
* - 类上还有其他注解
* - @Component
* - @ComponentScan
* - @Import
* - @ImportResource
* - 类有@Bean标识的方法
*/
List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
String[] candidateNames = registry.getBeanDefinitionNames(); // 缓存在beanDefinitionNames中的名称
for (String beanName : candidateNames) {
BeanDefinition beanDef = registry.getBeanDefinition(beanName); // 缓存在beanDefinitionMap中的BeanDefinition
if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
if (logger.isDebugEnabled()) {
logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
}
}
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) { // 判定是full型配置类还是lite型配置类
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
// Return immediately if no @Configuration classes were found
if (configCandidates.isEmpty()) {
return;
}
// Sort by previously determined @Order value, if applicable
// 配置类按照@Order标识的优先级升序
configCandidates.sort((bd1, bd2) -> {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return Integer.compare(i1, i2);
});
// Detect any custom bean name generation strategy supplied through the enclosing application context
SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet) {
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(
AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR); // Bean名称生成器 配置类即将被封装成BeanDefinition放到Bean工厂 注册BeanDefinition时要指定名称
if (generator != null) {
this.componentScanBeanNameGenerator = generator;
this.importBeanNameGenerator = generator;
}
}
}
if (this.environment == null) {
this.environment = new StandardEnvironment();
}
// Parse each @Configuration class
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates); // 配置类(full型和lite型)
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
do {
StartupStep processConfig = this.applicationStartup.start("spring.context.config-classes.parse");
/**
* 解析配置类
* - @Configuration标识的类封装成BeanDefinition注册到BeanFactory
* - @ComponentScan扫描的类封装成BeanDefinition注册到BeanFactory
* @Import和@Bean注解的类不会封装成BeanDefinition
*/
parser.parse(candidates);
parser.validate();
Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
configClasses.removeAll(alreadyParsed);
// Read the model and create bean definitions based on its content
if (this.reader == null) {
this.reader = new ConfigurationClassBeanDefinitionReader(
registry, this.sourceExtractor, this.resourceLoader, this.environment,
this.importBeanNameGenerator, parser.getImportRegistry());
}
/**
* 将解析出来的配置类封装成BeanDefinition注册进BeanFactory
* @Import和@Bean注册的Bean在这一步被解析成BeanDefinition注册到Bean工厂
*/
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);
processConfig.tag("classCount", () -> String.valueOf(configClasses.size())).end();
candidates.clear();
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set<String> oldCandidateNames = Set.of(candidateNames);
Set<String> alreadyParsedClasses = new HashSet<>();
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
for (String candidateName : newCandidateNames) {
if (!oldCandidateNames.contains(candidateName)) {
BeanDefinition bd = registry.getBeanDefinition(candidateName);
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
!alreadyParsedClasses.contains(bd.getBeanClassName())) {
// 还没解析的类加到集合中轮询到下一个loop中
candidates.add(new BeanDefinitionHolder(bd, candidateName));
}
}
}
candidateNames = newCandidateNames;
}
}
while (!candidates.isEmpty());
// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}
// Store the PropertySourceDescriptors to contribute them Ahead-of-time if necessary
this.propertySourceDescriptors = parser.getPropertySourceDescriptors();
if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory cachingMetadataReaderFactory) {
// Clear cache in externally provided MetadataReaderFactory; this is a no-op
// for a shared cache since it'll be cleared by the ApplicationContext.
cachingMetadataReaderFactory.clearCache();
}
}
1 配置类解析
2 BeanDefinition注册Bean工厂
上面parse(...)阶段
-
可能发生BeanDefinition注册Bean工厂
-
可能在配置类中缓存了
- importBeanDefinitionRegistrars
- @Import注解导入了实现了ImportBeanDefinitionRegistrar的类
- imports
- @Import注解导入的类(没有实现ImportSelector接口和ImportBeanDefinitionRegistrar接口)
- importedResources
- @ImportResource导入的配置文件
- beanMethods
- @Bean标识的方法
- importBeanDefinitionRegistrars
// ConfigurationClassPostProcessor.java
/**
* 上面parse(...)阶段
* - 可能发生BeanDefinition注册Bean工厂
* - 可能在配置类中缓存了
* - importBeanDefinitionRegistrars
* - @Import注解导入了实现了ImportBeanDefinitionRegistrar的类
* - imports
* - @Import注解导入的类(没有实现ImportSelector接口和ImportBeanDefinitionRegistrar接口)
* - importedResources
* - @ImportResource导入的配置文件
* - beanMethods
* - @Bean标识的方法
*
*/
this.reader.loadBeanDefinitions(configClasses);
// ConfigurationClassBeanDefinitionReader.java
public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
for (ConfigurationClass configClass : configurationModel) {
loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
}
}
// ConfigurationClassBeanDefinitionReader.java
private void loadBeanDefinitionsForConfigurationClass(
ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {
if (trackedConditionEvaluator.shouldSkip(configClass)) {
String beanName = configClass.getBeanName();
if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
this.registry.removeBeanDefinition(beanName);
}
this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
return;
}
if (configClass.isImported()) { // 配置类是被@Import进来的
registerBeanDefinitionForImportedConfigurationClass(configClass); // 导入进来的类是个配置类 封装成BeanDefinition注册Bean工厂
}
for (BeanMethod beanMethod : configClass.getBeanMethods()) { // 缓存着@Bean方法
loadBeanDefinitionsForBeanMethod(beanMethod); // @Bean注解的方法 方法返回值类型的类封装成BeanDefinition注册Bean工厂
}
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources()); // @ImportResource导入的配置文件
// @Import注册的Bean实现了ImportBeanDefinitionRegistrar 回调这个接口的registerBeanDefinitions方法
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}
四 BeanFactoryPostProcessor抽象回调
// ConfigurationClassPostProcessor.java
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
int factoryId = System.identityHashCode(beanFactory);
if (this.factoriesPostProcessed.contains(factoryId)) {
throw new IllegalStateException(
"postProcessBeanFactory already called on this post-processor against " + beanFactory);
}
/**
* Bean工厂后置处理器
* - 超类 BeanFactoryPostProcessor回调postProcessBeanFactory方法
* - 子类 BeanDefinitionRegistryPostProcessor回调postProcessBeanDefinitionRegistry
* 两个两调中都会处理配置类
* 避免重复执行通过id进行标识后置处理器是否已经处理过配置类
*/
this.factoriesPostProcessed.add(factoryId);
if (!this.registriesPostProcessed.contains(factoryId)) {
// BeanDefinitionRegistryPostProcessor hook apparently not supported...
// Simply call processConfigurationClasses lazily at this point then.
processConfigBeanDefinitions((BeanDefinitionRegistry) beanFactory);
}
/**
* beanFactory实现是DefaultListableBeanFactory
* @Configuration(proxyBeanMethods=true)标识的full型配置类的Bean类进行增强
* - 这个时候还没发生Bean实例化/初始化
* - 仅仅是将BeanDefinition已经注册在了Bean工厂中
* - 此时将BeanDefinition中Bean的Class进行增强
* - 将来进行实例化时回调
*/
this.enhanceConfigurationClasses(beanFactory);
// 向Bean工厂注册一个Bean后置处理器
beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));
}