发布时间：2023-09-28 10:30
ConfigurationClassPostProcessor是Spring中自动装配最核心的类，通过分析各个类的信息封装成BeanDifinition,他是一个后置处理器的类，如果弄懂了ConfigurationClassPostProcessor的处理方式，那么Spring和Spring Boot的装配逻辑也就明白了，此类中有很多递归调用，考虑了很多场景，所以流程图中流程之间的联系较为负责，但是当你看懂了全局以后，无法就是递归、再递归，不放过任何可能。
主要功能如下
1、解析@Configuration的配置类
2、解析@ComponentScan扫描的包
3、解析@ComponentScans扫描的包
4、解析@Import注解
5、解析@Component注解，包含继承了@Component的注解
6、解析@ImportResource
7、解析@Bean
.......
1、能力有限，图有点丑
2、下面是图片，但是在这里持续完善
/*
* Copyright 2002-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the \"License\");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an \"AS IS\" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.context.annotation;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.aop.framework.autoproxy.AutoProxyUtils;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter;
import org.springframework.beans.factory.config.SingletonBeanRegistry;
import org.springframework.beans.factory.parsing.FailFastProblemReporter;
import org.springframework.beans.factory.parsing.PassThroughSourceExtractor;
import org.springframework.beans.factory.parsing.ProblemReporter;
import org.springframework.beans.factory.parsing.SourceExtractor;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.BeanNameGenerator;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.context.annotation.ConfigurationClassEnhancer.EnhancedConfiguration;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;
import org.springframework.core.env.Environment;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.MethodMetadata;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
/**
* 此类是一个后置处理器的类，主要功能是参与BeanFactory的建造，主要功能如下
* 1、解析加了@Configuration的配置类
* 2、解析@ComponentScan扫描的包
* 3、解析@ComponentScans扫描的包
* 4、解析@Import注解
*
* {@link BeanFactoryPostProcessor} used for bootstrapping processing of
* {@link Configuration @Configuration} classes.
*
* Registered by default when using {@code
This post processor is priority-ordered as it is important that any
* {@link Bean} methods declared in {@code @Configuration} classes have
* their corresponding bean definitions registered before any other
* {@link BeanFactoryPostProcessor} executes.
*
* @author Chris Beams
* @author Juergen Hoeller
* @author Phillip Webb
* @since 3.0
*/
public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,
PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {
/**
* 使用类的全限定名作为bean的默认生成策略
*
* A {@code BeanNameGenerator} using fully qualified class names as default bean names.
*
This default for configuration-level import purposes may be overridden through
* {@link #setBeanNameGenerator}. Note that the default for component scanning purposes
* is a plain {@link AnnotationBeanNameGenerator#INSTANCE}, unless overridden through
* {@link #setBeanNameGenerator} with a unified user-level bean name generator.
* @since 5.2
* @see #setBeanNameGenerator
*/
public static final AnnotationBeanNameGenerator IMPORT_BEAN_NAME_GENERATOR =
new FullyQualifiedAnnotationBeanNameGenerator();
private static final String IMPORT_REGISTRY_BEAN_NAME =
ConfigurationClassPostProcessor.class.getName() + \".importRegistry\";
private final Log logger = LogFactory.getLog(getClass());
private SourceExtractor sourceExtractor = new PassThroughSourceExtractor();
private ProblemReporter problemReporter = new FailFastProblemReporter();
@Nullable
private Environment environment;
private ResourceLoader resourceLoader = new DefaultResourceLoader();
@Nullable
private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();
private MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory();
private boolean setMetadataReaderFactoryCalled = false;
private final Set registriesPostProcessed = new HashSet<>();
private final Set factoriesPostProcessed = new HashSet<>();
@Nullable
private ConfigurationClassBeanDefinitionReader reader;
// 是否使用本地xml配置的beanNameGenerator生成器
private boolean localBeanNameGeneratorSet = false;
/* Using short class names as default bean names by default. */
// 使用短类名作为bean名称生成策略
private BeanNameGenerator componentScanBeanNameGenerator = AnnotationBeanNameGenerator.INSTANCE;
/* Using fully qualified class names as default bean names by default. */
// 使用类的全限定名作为bean默认生成策略
private BeanNameGenerator importBeanNameGenerator = IMPORT_BEAN_NAME_GENERATOR;
@Override
public int getOrder() {
return Ordered.LOWEST_PRECEDENCE; // within PriorityOrdered
}
/**
* Set the {@link SourceExtractor} to use for generated bean definitions
* that correspond to {@link Bean} factory methods.
*/
public void setSourceExtractor(@Nullable SourceExtractor sourceExtractor) {
this.sourceExtractor = (sourceExtractor != null ? sourceExtractor : new PassThroughSourceExtractor());
}
/**
* Set the {@link ProblemReporter} to use.
* Used to register any problems detected with {@link Configuration} or {@link Bean}
* declarations. For instance, an @Bean method marked as {@code final} is illegal
* and would be reported as a problem. Defaults to {@link FailFastProblemReporter}.
*/
public void setProblemReporter(@Nullable ProblemReporter problemReporter) {
this.problemReporter = (problemReporter != null ? problemReporter : new FailFastProblemReporter());
}
/**
* Set the {@link MetadataReaderFactory} to use.
*
Default is a {@link CachingMetadataReaderFactory} for the specified
* {@linkplain #setBeanClassLoader bean class loader}.
*/
public void setMetadataReaderFactory(MetadataReaderFactory metadataReaderFactory) {
Assert.notNull(metadataReaderFactory, \"MetadataReaderFactory must not be null\");
this.metadataReaderFactory = metadataReaderFactory;
this.setMetadataReaderFactoryCalled = true;
}
/**
* Set the {@link BeanNameGenerator} to be used when triggering component scanning
* from {@link Configuration} classes and when registering {@link Import}\'ed
* configuration classes. The default is a standard {@link AnnotationBeanNameGenerator}
* for scanned components (compatible with the default in {@link ClassPathBeanDefinitionScanner})
* and a variant thereof for imported configuration classes (using unique fully-qualified
* class names instead of standard component overriding).
*
Note that this strategy does not apply to {@link Bean} methods.
*
This setter is typically only appropriate when configuring the post-processor as a
* standalone bean definition in XML, e.g. not using the dedicated {@code AnnotationConfig*}
* application contexts or the {@code } element. Any bean name
* generator specified against the application context will take precedence over any set here.
* @since 3.1.1
* @see AnnotationConfigApplicationContext#setBeanNameGenerator(BeanNameGenerator)
* @see AnnotationConfigUtils#CONFIGURATION_BEAN_NAME_GENERATOR
*/
public void setBeanNameGenerator(BeanNameGenerator beanNameGenerator) {
Assert.notNull(beanNameGenerator, \"BeanNameGenerator must not be null\");
this.localBeanNameGeneratorSet = true;
this.componentScanBeanNameGenerator = beanNameGenerator;
this.importBeanNameGenerator = beanNameGenerator;
}
@Override
public void setEnvironment(Environment environment) {
Assert.notNull(environment, \"Environment must not be null\");
this.environment = environment;
}
@Override
public void setResourceLoader(ResourceLoader resourceLoader) {
Assert.notNull(resourceLoader, \"ResourceLoader must not be null\");
this.resourceLoader = resourceLoader;
if (!this.setMetadataReaderFactoryCalled) {
this.metadataReaderFactory = new CachingMetadataReaderFactory(resourceLoader);
}
}
@Override
public void setBeanClassLoader(ClassLoader beanClassLoader) {
this.beanClassLoader = beanClassLoader;
if (!this.setMetadataReaderFactoryCalled) {
this.metadataReaderFactory = new CachingMetadataReaderFactory(beanClassLoader);
}
}
/**
* 定位、加载、解析、注册相关注解
*
* Derive further bean definitions from the configuration classes in the registry.
*/
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
// 根据对应的registry对象生成hashcode值，此对象只会操作一次，如果之前处理过则抛出异常
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);
}
// 将马上要进行处理的registry对象的id值放到已经处理的集合对象中
this.registriesPostProcessed.add(registryId);
// 处理配置类的bean定义信息
processConfigBeanDefinitions(registry);
}
/**
* 添加CGLIB增强处理及ImportAwareBeanPostProcessor后置处理类
*
* 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));
}
/**
* 构建和验证一个类是否被@Configuration修饰，并做相关的解析工作
*
* 如果你对此方法了解清楚了，那么springboot的自动装配原理就清楚了
*
* Build and validate a configuration model based on the registry of
* {@link Configuration} classes.
*/
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
// 创建存放BeanDefinitionHolder的对象集合
List configCandidates = new ArrayList<>();
// 当前registry就是DefaultListableBeanFactory，获取所有已经注册的BeanDefinition的beanName
String[] candidateNames = registry.getBeanDefinitionNames();
// 遍历所有要处理的beanDefinition的名称,筛选对应的beanDefinition（被注解修饰的）
for (String beanName : candidateNames) {
// 获取指定名称的BeanDefinition对象
BeanDefinition beanDef = registry.getBeanDefinition(beanName);
// 如果beanDefinition中的configurationClass属性不等于空，那么意味着已经处理过，输出日志信息
if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
if (logger.isDebugEnabled()) {
logger.debug(\"Bean definition has already been processed as a configuration class: \" + beanDef);
}
}
// 判断当前BeanDefinition是否是一个配置类，并为BeanDefinition设置属性为lite或者full，此处设置属性值是为了后续进行调用
// 如果Configuration配置proxyBeanMethods代理为true则为full
// 如果加了@Bean、@Component、@ComponentScan、@Import、@ImportResource注解，则设置为lite
// 如果配置类上被@Order注解标注，则设置BeanDefinition的order属性值
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
// 添加到对应的集合对象中
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
// Return immediately if no @Configuration classes were found
// 如果没有发现任何配置类，则直接返回
if (configCandidates.isEmpty()) {
return;
}
// Sort by previously determined @Order value, if applicable
// 如果适用，则按照先前确定的@Order的值排序
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
// 判断当前类型是否是SingletonBeanRegistry类型
SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
// 类型的强制转换
sbr = (SingletonBeanRegistry) registry;
// 判断是否有自定义的beanName生成器
if (!this.localBeanNameGeneratorSet) {
// 获取自定义的beanName生成器
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(
AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR);
// 如果有自定义的命名生成策略
if (generator != null) {
//设置组件扫描的beanName生成策略
this.componentScanBeanNameGenerator = generator;
// 设置import bean name生成策略
this.importBeanNameGenerator = generator;
}
}
}
// 如果环境对象等于空，那么就重新创建新的环境对象
if (this.environment == null) {
this.environment = new StandardEnvironment();
}
// Parse each @Configuration class
// 实例化ConfigurationClassParser类，并初始化相关的参数，完成配置类的解析工作
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
// 创建两个集合对象，
// 存放相关的BeanDefinitionHolder对象
Set candidates = new LinkedHashSet<>(configCandidates);
// 存放扫描包下的所有bean
Set alreadyParsed = new HashSet<>(configCandidates.size());
do {
// 解析带有@Controller、@Import、@ImportResource、@ComponentScan、@ComponentScans、@Bean的BeanDefinition
parser.parse(candidates);
// 将解析完的Configuration配置类进行校验，1、配置类不能是final，2、@Bean修饰的方法必须可以重写以支持CGLIB
parser.validate();
// 获取所有的bean,包括扫描的bean对象，@Import导入的bean对象
Set configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
// 清除掉已经解析处理过的配置类
configClasses.removeAll(alreadyParsed);
// Read the model and create bean definitions based on its content
// 判断读取器是否为空，如果为空的话，就创建完全填充好的ConfigurationClass实例的读取器
if (this.reader == null) {
this.reader = new ConfigurationClassBeanDefinitionReader(
registry, this.sourceExtractor, this.resourceLoader, this.environment,
this.importBeanNameGenerator, parser.getImportRegistry());
}
// 核心方法，将完全填充好的ConfigurationClass实例转化为BeanDefinition注册入IOC容器
this.reader.loadBeanDefinitions(configClasses);
// 添加到已经处理的集合中
alreadyParsed.addAll(configClasses);
candidates.clear();
// 这里判断registry.getBeanDefinitionCount() > candidateNames.length的目的是为了知道reader.loadBeanDefinitions(configClasses)这一步有没有向BeanDefinitionMap中添加新的BeanDefinition
// 实际上就是看配置类(例如AppConfig类会向BeanDefinitionMap中添加bean)
// 如果有，registry.getBeanDefinitionCount()就会大于candidateNames.length
// 这样就需要再次遍历新加入的BeanDefinition，并判断这些bean是否已经被解析过了，如果未解析，需要重新进行解析
// 这里的AppConfig类向容器中添加的bean，实际上在parser.parse()这一步已经全部被解析了
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
Set alreadyParsedClasses = new HashSet<>();
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
// 如果有未解析的类，则将其添加到candidates中，这样candidates不为空，就会进入到下一次的while的循环中
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 && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}
if (this.metadataReaderFactory instanceof 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) this.metadataReaderFactory).clearCache();
}
}
/**
* Post-processes a BeanFactory in search of Configuration class BeanDefinitions;
* any candidates are then enhanced by a {@link ConfigurationClassEnhancer}.
* Candidate status is determined by BeanDefinition attribute metadata.
* @see ConfigurationClassEnhancer
*/
public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFactory) {
Map configBeanDefs = new LinkedHashMap<>();
for (String beanName : beanFactory.getBeanDefinitionNames()) {
BeanDefinition beanDef = beanFactory.getBeanDefinition(beanName);
Object configClassAttr = beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE);
MethodMetadata methodMetadata = null;
if (beanDef instanceof AnnotatedBeanDefinition) {
methodMetadata = ((AnnotatedBeanDefinition) beanDef).getFactoryMethodMetadata();
}
if ((configClassAttr != null || methodMetadata != null) && beanDef instanceof AbstractBeanDefinition) {
// Configuration class (full or lite) or a configuration-derived @Bean method
// -> resolve bean class at this point...
AbstractBeanDefinition abd = (AbstractBeanDefinition) beanDef;
if (!abd.hasBeanClass()) {
try {
abd.resolveBeanClass(this.beanClassLoader);
}
catch (Throwable ex) {
throw new IllegalStateException(
\"Cannot load configuration class: \" + beanDef.getBeanClassName(), ex);
}
}
}
if (ConfigurationClassUtils.CONFIGURATION_CLASS_FULL.equals(configClassAttr)) {
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.isInfoEnabled() && beanFactory.containsSingleton(beanName)) {
logger.info(\"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 entry : configBeanDefs.entrySet()) {
AbstractBeanDefinition beanDef = entry.getValue();
// If a @Configuration class gets proxied, always proxy the target class
beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
// Set enhanced subclass of the user-specified bean class
Class configClass = beanDef.getBeanClass();
Class enhancedClass = enhancer.enhance(configClass, this.beanClassLoader);
if (configClass != enhancedClass) {
if (logger.isTraceEnabled()) {
logger.trace(String.format(\"Replacing bean definition \'%s\' existing class \'%s\' with \" +
\"enhanced class \'%s\'\", entry.getKey(), configClass.getName(), enhancedClass.getName()));
}
beanDef.setBeanClass(enhancedClass);
}
}
}
private static class ImportAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter {
private final BeanFactory beanFactory;
public ImportAwareBeanPostProcessor(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
/**
* 如果配置类有Configuration注解，会进行动态代理，会实现EnhancedConfiguration接口，里面有个setBeanFactory接口方法，会传入beanFactory
* @param pvs
* @param bean
* @param beanName
* @return
*/
@Override
public PropertyValues postProcessProperties(@Nullable PropertyValues pvs, Object bean, String beanName) {
// Inject the BeanFactory before AutowiredAnnotationBeanPostProcessor\'s
// postProcessProperties method attempts to autowire other configuration beans.
if (bean instanceof EnhancedConfiguration) {
((EnhancedConfiguration) bean).setBeanFactory(this.beanFactory);
}
return pvs;
}
/**
* 如果是ImportAware类型的，就会设置bean的注解信息
* @param bean
* @param beanName
* @return
*/
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) {
if (bean instanceof ImportAware) {
ImportRegistry ir = this.beanFactory.getBean(IMPORT_REGISTRY_BEAN_NAME, ImportRegistry.class);
AnnotationMetadata importingClass = ir.getImportingClassFor(ClassUtils.getUserClass(bean).getName());
if (importingClass != null) {
((ImportAware) bean).setImportMetadata(importingClass);
}
}
return bean;
}
}
}