类结构图：
image.png
通过类图发现有两个比较关键接口BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor；而BeanDefinitionRegistryPostProcessor继承了BeanFactoryPostProcessor接口
对BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor不了解的朋友可以查看
Spring Boot 源码分析 —— 后置处理器
Spring Boot 源码分析 —— BeanDefinitionRegistryPostProcessor接口
源码分析
/**
* Derive further bean definitions from the configuration classes in the registry.
*/
@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);
processConfigBeanDefinitions(registry);
}
/**
* Prepare the Configuration classes for servicing bean requests at runtime
* by replacing them with CGLIB-enhanced subclasses.
*/
@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);
}
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);
}
enhanceConfigurationClasses(beanFactory);
beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));
}
postProcessBeanDefinitionRegistry()
processConfigBeanDefinitions(registry);
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
List<BeanDefinitionHolder> configCandidates = new ArrayList<BeanDefinitionHolder>();
String[] candidateNames = registry.getBeanDefinitionNames();
for (String beanName : candidateNames) {
BeanDefinition beanDef = registry.getBeanDefinition(beanName);
//如果BeanDefinition 中的configurationClass 属性为full或者lite,已经处理过了,直接跳过
if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
if (logger.isDebugEnabled()) {
logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
}
}
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
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
// 获取@Order值进行排序
Collections.sort(configCandidates, new Comparator<BeanDefinitionHolder>() {
@Override
public int compare(BeanDefinitionHolder bd1, BeanDefinitionHolder bd2) {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return (i1 < i2) ? -1 : (i1 > i2) ? 1 : 0;
}
});
// Detect any custom bean name generation strategy supplied through the enclosing application context
//强制类型转换，由于我们当前传入的是DefaultListableBeanFactory是SingletonBeanRegistry的子类。因此会将registry强转为SingletonBeanRegistry
SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet && sbr.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) {
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
this.componentScanBeanNameGenerator = generator;
this.importBeanNameGenerator = generator;
}
}
// Parse each @Configuration class
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<BeanDefinitionHolder>(configCandidates);
Set<ConfigurationClass> alreadyParsed = new HashSet<ConfigurationClass>(configCandidates.size());
//循环解析@Configuration类
do {
parser.parse(candidates);
parser.validate();
Set<ConfigurationClass> configClasses = new LinkedHashSet<ConfigurationClass>(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());
}
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);
candidates.clear();
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set<String> oldCandidateNames = new HashSet<String>(Arrays.asList(candidateNames));
Set<String> alreadyParsedClasses = new HashSet<String>();
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())) {
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) {
if (!sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}
}
if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
}
}
postProcessBeanFactory()
enhanceConfigurationClasses(beanFactory);
public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFactory) {
Map<String, AbstractBeanDefinition> configBeanDefs = new LinkedHashMap<String, AbstractBeanDefinition>();
//循环遍历容器中所有BeanDefinitionName
for (String beanName : beanFactory.getBeanDefinitionNames()) {
//通过BeanDefinitionName获取BeanDefinition
BeanDefinition beanDef = beanFactory.getBeanDefinition(beanName);
//如果BeanDefinition 中的configurationClass 属性为full已经处理过了,直接跳过
if (ConfigurationClassUtils.isFullConfigurationClass(beanDef)) {
if (!(beanDef instanceof AbstractBeanDefinition)) {
throw new BeanDefinitionStoreException("Cannot enhance @Configuration bean definition '" +
beanName + "' since it is not stored in an AbstractBeanDefinition subclass");
}
else if (logger.isWarnEnabled() && beanFactory.containsSingleton(beanName)) {
logger.warn("Cannot enhance @Configuration bean definition '" + beanName +
"' since its singleton instance has been created too early. The typical cause " +
"is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor " +
"return type: Consider declaring such methods as 'static'.");
}
configBeanDefs.put(beanName, (AbstractBeanDefinition) beanDef);
}
}
if (configBeanDefs.isEmpty()) {
// nothing to enhance -> return immediately
return;
}
ConfigurationClassEnhancer enhancer = new ConfigurationClassEnhancer();
for (Map.Entry<String, AbstractBeanDefinition> entry : configBeanDefs.entrySet()) {
AbstractBeanDefinition beanDef = entry.getValue();
// If a @Configuration class gets proxied, always proxy the target class 如果是Configuration注解类，修改BeanDifination设置属性为总是被代理
beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
try {
// Set enhanced subclass of the user-specified bean class 设置用户指定的bean类的子类增强
Class<?> configClass = beanDef.resolveBeanClass(this.beanClassLoader);
Class<?> enhancedClass = enhancer.enhance(configClass, this.beanClassLoader);
if (configClass != enhancedClass) {
if (logger.isDebugEnabled()) {
logger.debug(String.format("Replacing bean definition '%s' existing class '%s' with " +
"enhanced class '%s'", entry.getKey(), configClass.getName(), enhancedClass.getName()));
}
beanDef.setBeanClass(enhancedClass);
}
}
catch (Throwable ex) {
throw new IllegalStateException("Cannot load configuration class: " + beanDef.getBeanClassName(), ex);
}
}
}
总结：
processConfigBeanDefinitions()方法实现：
处理所有@Configuration类，解析配置类@ComponentScans、@ComponentScan、@ImportResource...等注解配置信息
postProcessBeanFactory()方法实现
当前类如果是Configuration注解类，修改当前类的BeanDifination，设置属性为总是被代理
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