ConfigurationClassPostProcessor
前面说到ConfigurationClassPostProcessor是BeanDefinitionRegistryPostProcessor接口的实现，在调用invokeBeanFactoryPostProcessors时，会先被调用；而且通过之前的分析我们可以知道，它是在容器初始化置AnnotatedBeanDefinitionReader时注册到注册的（分析(二)），主要用来处理@Configuration注解。因实现还是比较复杂的，所以单独拿出来分析下。
先看一下该类实现的接口
public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor, PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {
....
}
它除了是BeanDefinitionRegistryPostProcessor的实现之外，还实现了一堆的Aware接口。我们在前面有介绍ApplicationContextAwareProcessor这个bean的扩展实现的功能，注入上下文属性（在调用getBean进行实例化时调用的，关于getBean调用过程后面再介绍）。
1. postProcessBeanDefinitionRegistry
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);
}
代码比较简单，取得registry的id并做判重处理或记录，直接看processConfigBeanDefinitions方法，代码如下.
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
// 获取容器中注册的所有bean名字
String[] candidateNames = registry.getBeanDefinitionNames();
//遍历bean
for (String beanName : candidateNames) {
BeanDefinition beanDef = registry.getBeanDefinition(beanName);
//判断bean是否已经处理过
if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
if (logger.isDebugEnabled()) {
logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
}
}
// 判断是否是Configuration类, 这里其实主要是看是否有
// @Configuration, @Component, @ComponentScan, @Import, @Bean等注解
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
// 这里筛选完之后，符合条件的只剩启动类 @SpringBootApplication
if (configCandidates.isEmpty()) {
return;
}
// 排序
configCandidates.sort((bd1, bd2) -> {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return Integer.compare(i1, i2);
});
// 设置beanName的生成策略
SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet) {
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
if (generator != null) {
this.componentScanBeanNameGenerator = generator;
this.importBeanNameGenerator = generator;
}
}
}
if (this.environment == null) {
this.environment = new StandardEnvironment();
}
// 配置@Configuration的解析器，这里的部分属性就是通过ApplicationContextAwareProcessor来设置注入的。
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
// 解析
do {
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());
}
// 读取配置类，加载beanDefinition
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);
candidates.clear();
// 如果在解析过程中，有新的配置类型beanDefinition注册加入，则循环处理
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(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())) {
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());
}
// 清除缓存
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();
}
}
- 获取已经注册的bean名称,进行遍历; 判断是否已经处理过，判断是否为配置类；如果有，排下序。
- 如果BeanDefinitionRegistry 是SingletonBeanRegistry 子类的话,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；然后获取beanName的生成策略设置给成员变量。
- 实例化ConfigurationClassParser 为了解析各个配置类.实例化2个set,candidates 用于将之前加入的configCandidates 进行去重,alreadyParsed 用于判断是否处理过。
- 调用ConfigurationClassParser#parse进行解析 将解析过的配置类加入到configClasses；实例化ConfigurationClassBeanDefinitionReader 调用ConfigurationClassBeanDefinitionReader#loadBeanDefinitions 进行加载,并加入到alreadyParsed中,用于去重 将candidates进行清空,如果registry中注册的bean的数量 大于 之前获得的数量,则意味着在解析过程中又新加入了很多,那么就需要对其进行解析
- 注册一个,bean 为 ImportRegistry；清除缓存。
这里有一个判断是否为配置类的方法，其实检查的就是该类是否有@Configuration,@Component,@ComponentScan, @Import, @ImportResource, @Bean方法。
2. ConfigurationClassParser.parse
该方法的代码简单，最后调用会到processConfigurationClass方法，我们直接看该方法实现。
processConfigurationClass
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
//是否跳过
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}
ConfigurationClass existingClass = this.configurationClasses.get(configClass);
// 处理Imported 的情况
if (existingClass != null) {
if (configClass.isImported()) {
if (existingClass.isImported()) {
existingClass.mergeImportedBy(configClass);
}
// Otherwise ignore new imported config class; existing non-imported class overrides it.
return;
}
else {
// Explicit bean definition found, probably replacing an import.
this.configurationClasses.remove(configClass);
this.knownSuperclasses.values().removeIf(configClass::equals);
}
}
// Recursively process the configuration class and its superclass hierarchy.
SourceClass sourceClass = asSourceClass(configClass);
do {
sourceClass = doProcessConfigurationClass(configClass, sourceClass);
}
while (sourceClass != null);
this.configurationClasses.put(configClass, configClass);
}
- 先看ConditionEvaluator.shouldSkip判断是否跳过，根据@Condition条件来判断。
- 判断处理imported的情况
- 递归解析configClass
3. doProcessConfigurationClass
解析class配置的核心方法，代码如下:
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// 首先递归处理内部类
processMemberClasses(configClass, sourceClass);
// 处理 @PropertySource 注解
for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), PropertySources.class,
org.springframework.context.annotation.PropertySource.class)) {
if (this.environment instanceof ConfigurableEnvironment) {
processPropertySource(propertySource);
}
else {
logger.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
"]. Reason: Environment must implement ConfigurableEnvironment");
}
}
// 处理 @ComponentScan 类
Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
for (AnnotationAttributes componentScan : componentScans) {
// 如果配置类有@ComponentScan -> 立刻运行扫描
Set<BeanDefinitionHolder> scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// 检查扫描到的definition是否还有配置类型，有则递归解析
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
// 处理 @Import 注解
processImports(configClass, sourceClass, getImports(sourceClass), true);
// 处理 @ImportResource 注解
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
String[] resources = importResource.getStringArray("locations");
Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}
// 处理 @Bean 方法注解
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// 处理接口的默认方法
processInterfaces(configClass, sourceClass);
// 处理父类
if (sourceClass.getMetadata().hasSuperClass()) {
String superclass = sourceClass.getMetadata().getSuperClassName();
if (superclass != null && !superclass.startsWith("java") &&
!this.knownSuperclasses.containsKey(superclass)) {
this.knownSuperclasses.put(superclass, configClass);
// Superclass found, return its annotation metadata and recurse
return sourceClass.getSuperClass();
}
}
// No superclass -> processing is complete
return null;
}
3.1 处理内部类，不再贴代码；
- 遍历configClass的内部类，判断是否为配置类且类名不与configClass相同
- 判断是否存在循环引用
3.2 处理@PropertySource.通过遍历该类中的@PropertySource的注解,如果该类中的environment是ConfigurableEnvironment 子类的话,则调用processPropertySource进行处理.否则打印警告日志.一般都是ConfigurableEnvironment的子类
private void processPropertySource(AnnotationAttributes propertySource) throws IOException {
//获取注解上的属性name
String name = propertySource.getString("name");
if (!StringUtils.hasLength(name)) {
name = null;
}
//获取注解上的属性encoding
String encoding = propertySource.getString("encoding");
if (!StringUtils.hasLength(encoding)) {
encoding = null;
}
String[] locations = propertySource.getStringArray("value");
Assert.isTrue(locations.length > 0, "At least one @PropertySource(value) location is required");
boolean ignoreResourceNotFound = propertySource.getBoolean("ignoreResourceNotFound");
// 获取Facotry，如果没指定使用默认的DefaultPropertySourceFactory
Class<? extends PropertySourceFactory> factoryClass = propertySource.getClass("factory");
PropertySourceFactory factory = (factoryClass == PropertySourceFactory.class ?
DEFAULT_PROPERTY_SOURCE_FACTORY : BeanUtils.instantiateClass(factoryClass));
for (String location : locations) {
try {
// 解析点位符，多环境配置
String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);
// 加载property配置文件
Resource resource = this.resourceLoader.getResource(resolvedLocation);
addPropertySource(factory.createPropertySource(name, new EncodedResource(resource, encoding)));
}
catch (IllegalArgumentException | FileNotFoundException | UnknownHostException ex) {
// Placeholders not resolvable or resource not found when trying to open it
if (ignoreResourceNotFound) {
if (logger.isInfoEnabled()) {
logger.info("Properties location [" + location + "] not resolvable: " + ex.getMessage());
}
}
else {
throw ex;
}
}
}
}
解析@PropertySource注解上的各属性值，加载配置文件，然后添加到运行环境中。
3.3 处理@ComponentScan：判断是否应该跳过，并依次通过ComponentScanAnnotationParser.parse进行解析。最终调用ClassPathBeanDefinitionScanner.doScan。代码如下:
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
// 扫描basePackage路径下的java文件
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
// 解析是否有@Scop
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
// 生成beanName
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
// 设置默认配置
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
// 通用注解的解析设置
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
// 判断beanName容器中是否存在，不存在则注册，如存在判断是否兼容，不兼容抛异常
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
那么，通过上面一步后，我们自己写的@Controller, @Service等就被注册到容器中了。只是完成了beanDefinition的查找，解析并注册的工作，此时这些bean还未被实例化。ok, 回到doProcessConfigurationClass方法中对@ComponentScan的解析处接着看，因为@Controller, @Service, @Configuration等注解都是符合配置类校验的（ConfigurationClassUtils.checkConfigurationClassCandidate），所以还需要递归解析来看其他内部是否还有其他配置，比如内部类，@Bean等。
接着再往下，以次解析的是@Import, @ImportResource, 收集@Bean方法与接口的默认方法。这部分不再一一分析，流程和上面类似递归处理，最后把configClass都放到了集合中。
解析处理完之后，回到我们的ConfigurationClassPostProcessor方法继续看，实例化了reader类ConfigurationClassBeanDefinitionReader用来读取加载configClass的解析。
public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
for (ConfigurationClass configClass : configurationModel) {
loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
}
}
private void loadBeanDefinitionsForConfigurationClass(
ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {
//如果应该跳过，且容器中有，则移除
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;
}
// 注册@Import
if (configClass.isImported()) {
registerBeanDefinitionForImportedConfigurationClass(configClass);
}
// @注册Bean
for (BeanMethod beanMethod : configClass.getBeanMethods()) {
loadBeanDefinitionsForBeanMethod(beanMethod);
}
// 注册@ImportResource 通过XmlBeanDefinitionReader读取配置
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
// 注册ImportBeanDefinitionRegistrar实现
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}
通过之前的分析，其实我们知道@PropertySource，@ComponentScan的解析最后会把相关注解增加到环境配置或者注册到容器中去。但对@Import, @Bean的只是收集到集合中，并未注册到容器中，所以上面的load主要处理这一部分。
- registerBeanDefinitionForImportedConfigurationClass 注册@Import
- loadBeanDefinitionsForBeanMethod 注册@Bean
- loadBeanDefinitionsFromImportedResources 注册@ImportResource 通过XmlBeanDefinitionReader读取配置
- loadBeanDefinitionsFromRegistrars 注册ImportBeanDefinitionRegistrar实现
processConfigBeanDefinitions方法再下面的处理就是判断新增的beanDefinition是否有配置类，有则递归处理，无则清除缓存。
该篇文章分析详细，建议阅读一下。
