Spring5源码解析6-ConfigurationClassParser 解析配置类 ConfigurationClassParser
在ConfigurationClassPostProcessor#processConfigBeanDefinitions方法中创建了ConfigurationClassParser对象并调用其parse方法。该方法就是在负责解析配置类、扫描包、注册BeanDefinition，源码如下：
//ConfigurationClassParser#parseSet) 方法源码
public void parse(Set configCandidates) {
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
// 根据不同的 BeanDefinition 实例对象 调用不同的 parse 方法
// 底层其实都是在调用 org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass
if (bd instanceof AnnotatedBeanDefinition) {
parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
} else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
} else {
parse(bd.getBeanClassName(), holder.getBeanName());
}
} catch (BeanDefinitionStoreException ex) {
throw ex;
} catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
}
}
//执行DeferredImportSelector
this.deferredImportSelectorHandler.process();
}
在该方法内部根据不同的BeanDefinition实例对象，调用了不同的parse方法，而这些parse方法底层，实际上都是调用了ConfigurationClassParser#processConfigurationClass方法。
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
// 是否需要跳过 @Conditional
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}
// 第一次进入的时候, configurationClasses size = 0,existingClass 肯定为 null
ConfigurationClass existingClass = this.configurationClasses.get(configClass);
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.
// Let's remove the old one and go with the new one.
this.configurationClasses.remove(configClass);
this.knownSuperclasses.values().removeIf(configClass::equals);
}
}
// Recursively process the configuration class and its superclass hierarchy.
SourceClass sourceClass = asSourceClass(configClass);
do {
// 真正的做解析
sourceClass = doProcessConfigurationClass(configClass, sourceClass);
}
while (sourceClass != null);
this.configurationClasses.put(configClass, configClass);
}
方法传入的ConfigurationClass对象是对配置类的封装。首先判断配置类上是否有@Conditional注解，是否需要跳过解析该配置类。
然后，调用doProcessConfigurationClass(configClass, sourceClass);做真正的解析。其中，configClass是程序的配置类，而sourceClass是通过configClass创建的。
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// @Configuration 继承了 @Component
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// Recursively process any member (nested) classes first
// 递归处理内部类
processMemberClasses(configClass, sourceClass);
}
// Process any @PropertySource annotations
// 处理@PropertySource
// @PropertySource注解用来加载properties文件
for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), PropertySources.class,
org.springframework.context.annotation.PropertySource.class)) {
if (this.environment instanceof ConfigurableEnvironment) {
processPropertySource(propertySource);
} else {
logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
"]. Reason: Environment must implement ConfigurableEnvironment");
}
}
// Process any @ComponentScan annotations
Set componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
for (AnnotationAttributes componentScan : componentScans) {
// The config class is annotated with @ComponentScan -> perform the scan immediately
Set scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// Check the set of scanned definitions for any further config classes and parse recursively if needed
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
//判断解析获取的 BeanDefinition 中 是否有配置类
// 这里的配置类包括FullConfigurationClass和LiteConfigurationClass
// 也就是说只要有@Configuration、@Component、@ComponentScan、@Import、@ImportResource和@Bean中的其中一个注解
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
//如果有配置类,递归调用,解析该配置类,这个if几乎都为true，这个方法几乎都要执行
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
// Process any @Import annotations
processImports(configClass, sourceClass, getImports(sourceClass), true);
// Process any @ImportResource annotations
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
String[] resources = importResource.getStringArray("locations");
Class readerClass = importResource.getClass("reader");
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}
// Process individual @Bean methods
//处理单个@Bean的方法
Set beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// Process default methods on interfaces
processInterfaces(configClass, sourceClass);
// Process superclass, if any
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;
}
解析内部类
配置类上有@Configuration注解，该注解继承 @Component，if 判断为true，调用processMemberClasses方法，递归解析配置类中的内部类。
解析@PropertySource注解
如果配置类上有@PropertySource注解，则解析加载properties文件，并将属性添加到Spring上下文中。((ConfigurableEnvironment) this.environment).getPropertySources().addFirstPropertySource(newSource);。
处理@ComponentScan注解
获取配置类上的@ComponentScan注解，判断是否需要跳过。循环所有的ComponentScan，立即执行扫描。ComponentScanAnnotationParser#parse方法如下：
public Set parse(AnnotationAttributes componentScan, final String declaringClass) {
// 创建 ClassPathBeanDefinitionScanner
// 在 AnnotationConfigApplicationContext 的构造器中也创建了一个ClassPathBeanDefinitionScanner
// 这里证明了,执行扫描 scanner 不是构造器中的,而是这里创建的
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
// @ComponentScan 中可以注册自定义的 BeanNameGenerator
// 但是需要注意,通过源码可以明白,这里注册的自定义BeanNameGenerator 只对当前 scanner 有效
Class generatorClass = componentScan.getClass("nameGenerator");
boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
BeanUtils.instantiateClass(generatorClass));
ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
scanner.setScopedProxyMode(scopedProxyMode);
} else {
Class resolverClass = componentScan.getClass("scopeResolver");
scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
}
scanner.setResourcePattern(componentScan.getString("resourcePattern"));
for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addIncludeFilter(typeFilter);
}
}
for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addExcludeFilter(typeFilter);
}
}
boolean lazyInit = componentScan.getBoolean("lazyInit");
if (lazyInit) {
scanner.getBeanDefinitionDefaults().setLazyInit(true);
}
Set basePackages = new LinkedHashSet<>();
String[] basePackagesArray = componentScan.getStringArray("basePackages");
for (String pkg : basePackagesArray) {
String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg),
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
Collections.addAll(basePackages, tokenized);
}
// @ComponentScan(basePackageClasses = Xx.class)
// 可以指定basePackageClasses, 只要是与是这几个类所在包及其子包,就可以被Spring扫描
// 经常会用一个空的类来作为basePackageClasses,默认取当前配置类所在包及其子包
for (Class clazz : componentScan.getClassArray("basePackageClasses")) {
basePackages.add(ClassUtils.getPackageName(clazz));
}
if (basePackages.isEmpty()) {
basePackages.add(ClassUtils.getPackageName(declaringClass));
}
scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {
@Override
protected boolean matchClassName(String className) {
return declaringClass.equals(className);
}
});
//执行扫描
return scanner.doScan(StringUtils.toStringArray(basePackages));
}
挑一些我觉得是重点的地方记录一下：
parse方法中新创建了一个ClassPathBeanDefinitionScanner对象，而在 AnnotationConfigApplicationContext 的构造器中也创建了一个ClassPathBeanDefinitionScanner对象，这里证实了在Spring内部，真正执行扫描的不是AnnotationConfigApplicationContext中的scanner。
通过源码可以了解到，在@ComponentScan中是可以注册自定义的 BeanNameGenerator的，而这个BeanNameGenerator只对当前scanner有效。也就是说，这个BeanNameGenerator只能影响通过该scanner扫描的路径下的bean的BeanName生成规则。
最后调用scanner.doScan(StringUtils.toStringArray(basePackages));方法执行真正的扫描，方法返回扫描获取到的BeanDefinition。
检验获得的BeanDefinition中是否有配置类
检验扫描获得的BeanDefinition中是否有配置类，如果有配置类，这里的配置类包括FullConfigurationClass和LiteConfigurationClass。（也就是说只要有@Configuration、@Component、@ComponentScan、@Import、@ImportResource和@Bean中的其中一个注解），则递归调用parse方法，进行解析。
解析 @Import 注解
processImports(configClass, sourceClass, getImports(sourceClass), true);
processImports方法负责对@Import注解进行解析。configClass是配置类，sourceClass又是通过configClass创建的，getImports(sourceClass)从sourceClass获取所有的@Import注解信息，然后调用ConfigurationClassParser#processImports。
// ConfigurationClassParser#processImports 源码
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection importCandidates, boolean checkForCircularImports) {
if (importCandidates.isEmpty()) {
return;
}
if (checkForCircularImports && isChainedImportOnStack(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
} else {
this.importStack.push(configClass);
try {
// importCandidates是@Import的封装
// 循环importCandidates对import的内容进行分类
for (SourceClass candidate : importCandidates) {
// import导入实现ImportSelector接口的类
if (candidate.isAssignable(ImportSelector.class)) {
// Candidate class is an ImportSelector -> delegate to it to determine imports
Class candidateClass = candidate.loadClass();
// 反射创建这个类的实例对象
ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
//是否有实现相关Aware接口,如果有,这调用相关方法
ParserStrategyUtils.invokeAwareMethods(
selector, this.environment, this.resourceLoader, this.registry);
// 延迟加载的ImportSelector
if (selector instanceof DeferredImportSelector) {
// 延迟加载的ImportSelector先放到List中,延迟加载
this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
} el