ConfigurationClassParser
在ConfigurationClassPostProcessor#processConfigBeanDefinitions方法中創建了ConfigurationClassParser對象並調用其parse方法。該方法就是在負責解析配置類、掃描包、注冊BeanDefinition，源碼如下：
//ConfigurationClassParser#parseSet<BeanDefinitionHolder>) 方法源碼
public void parse(Set<BeanDefinitionHolder> configCandidates) {
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
// 根據不同的 BeanDefinition 實例對象 調用不同的 parse 方法
// 底層其實都是在調用 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);
}
}
//執行DeferredImportSelector
this.deferredImportSelectorHandler.process();
}
在該方法內部根據不同的BeanDefinition實例對象，調用了不同的parse方法，而這些parse方法底層，實際上都是調用了ConfigurationClassParser#processConfigurationClass方法。
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
// 是否需要跳過 @Conditional
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}
// 第一次進入的時候, configurationClasses size = 0,existingClass 肯定為 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);
}
方法傳入的ConfigurationClass對象是對配置類的封裝。首先判斷配置類上是否有@Conditional注解，是否需要跳過解析該配置類。
然后，調用doProcessConfigurationClass(configClass, sourceClass);做真正的解析。其中，configClass是程序的配置類，而sourceClass是通過configClass創建的。
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// @Configuration 繼承了 @Component
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// Recursively process any member (nested) classes first
// 遞歸處理內部類
processMemberClasses(configClass, sourceClass);
}
// Process any @PropertySource annotations
// 處理@PropertySource
// @PropertySource注解用來加載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<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) {
// The config class is annotated with @ComponentScan -> perform the scan immediately
Set<BeanDefinitionHolder> 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();
}
//判斷解析獲取的 BeanDefinition 中 是否有配置類
// 這里的配置類包括FullConfigurationClass和LiteConfigurationClass
// 也就是說只要有@Configuration、@Component、@ComponentScan、@Import、@ImportResource和@Bean中的其中一個注解
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
//如果有配置類,遞歸調用,解析該配置類,這個if幾乎都為true，這個方法幾乎都要執行
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<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}
// Process individual @Bean methods
//處理單個@Bean的方法
Set<MethodMetadata> 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;
}
解析內部類
配置類上有@Configuration注解，該注解繼承 @Component，if 判斷為true，調用processMemberClasses方法，遞歸解析配置類中的內部類。
解析@PropertySource注解
如果配置類上有@PropertySource注解，則解析加載properties文件，並將屬性添加到Spring上下文中。((ConfigurableEnvironment) this.environment).getPropertySources().addFirstPropertySource(newSource);。
處理@ComponentScan注解
獲取配置類上的@ComponentScan注解，判斷是否需要跳過。循環所有的ComponentScan，立即執行掃描。ComponentScanAnnotationParser#parse方法如下：
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
// 創建 ClassPathBeanDefinitionScanner
// 在 AnnotationConfigApplicationContext 的構造器中也創建了一個ClassPathBeanDefinitionScanner
// 這里證明了,執行掃描 scanner 不是構造器中的,而是這里創建的
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
// @ComponentScan 中可以注冊自定義的 BeanNameGenerator
// 但是需要注意,通過源碼可以明白,這里注冊的自定義BeanNameGenerator 只對當前 scanner 有效
Class<? extends BeanNameGenerator> 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<? extends ScopeMetadataResolver> 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<String> 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, 只要是與是這幾個類所在包及其子包,就可以被Spring掃描
// 經常會用一個空的類來作為basePackageClasses,默認取當前配置類所在包及其子包
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);
}
});
//執行掃描
return scanner.doScan(StringUtils.toStringArray(basePackages));
}
挑一些我覺得是重點的地方記錄一下：
parse方法中新創建了一個ClassPathBeanDefinitionScanner對象，而在AnnotationConfigApplicationContext的構造器中也創建了一個ClassPathBeanDefinitionScanner對象，這里證實了在Spring內部，真正執行掃描的不是AnnotationConfigApplicationContext中的scanner。- 通過源碼可以了解到，在
@ComponentScan中是可以注冊自定義的BeanNameGenerator的，而這個BeanNameGenerator只對當前scanner有效。也就是說，這個BeanNameGenerator只能影響通過該scanner掃描的路徑下的bean的BeanName生成規則。 - 最后調用
scanner.doScan(StringUtils.toStringArray(basePackages));方法執行真正的掃描，方法返回掃描獲取到的BeanDefinition。
檢驗獲得的BeanDefinition中是否有配置類
檢驗掃描獲得的BeanDefinition中是否有配置類，如果有配置類，這里的配置類包括FullConfigurationClass和LiteConfigurationClass。（也就是說只要有@Configuration、@Component、@ComponentScan、@Import、@ImportResource和@Bean中的其中一個注解），則遞歸調用parse方法，進行解析。
解析 @Import 注解
processImports(configClass, sourceClass, getImports(sourceClass), true);
processImports方法負責對@Import注解進行解析。configClass是配置類，sourceClass又是通過configClass創建的，getImports(sourceClass)從sourceClass獲取所有的@Import注解信息，然后調用ConfigurationClassParser#processImports。
// ConfigurationClassParser#processImports 源碼
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection<SourceClass> 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的封裝
// 循環importCandidates對import的內容進行分類
for (SourceClass candidate : importCandidates) {
// import導入實現ImportSelector接口的類
if (candidate.isAssignable(ImportSelector.class)) {
// Candidate class is an ImportSelector -> delegate to it to determine imports
Class<?> candidateClass = candidate.loadClass();
// 反射創建這個類的實例對象
ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
//是否有實現相關Aware接口,如果有,這調用相關方法
ParserStrategyUtils.invokeAwareMethods(
selector, this.environment, this.resourceLoader, this.registry);
// 延遲加載的ImportSelector
if (selector instanceof DeferredImportSelector) {
// 延遲加載的ImportSelector先放到List中,延遲加載
this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
} else {
// 普通的ImportSelector ,執行其selectImports方法,獲取需要導入的類的全限定類名數組
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
// 遞歸調用
processImports(configClass, currentSourceClass, importSourceClasses, false);
}
// 是否為ImportBeanDefinitionRegistrar
} else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
// Candidate class is an ImportBeanDefinitionRegistrar ->
// delegate to it to register additional bean definitions
Class<?> candidateClass = candidate.loadClass();
ImportBeanDefinitionRegistrar registrar =
BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
ParserStrategyUtils.invokeAwareMethods(
registrar, this.environment, this.resourceLoader, this.registry);
// 添加到成員變量 org.springframework.context.annotation.ConfigurationClass.importBeanDefinitionRegistrars 中
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
} else {
// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
// process it as an @Configuration class
// 普通 @Configuration class
this.importStack.registerImport(
currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
// 解析導入的@Configuration class
processConfigurationClass(candidate.asConfigClass(configClass));
}
}
} catch (BeanDefinitionStoreException ex) {
throw ex;
} catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to process import candidates for configuration class [" +
configClass.getMetadata().getClassName() + "]", ex);
} finally {
this.importStack.pop();
}
}
}
解析 @ImportResource 注解
@ImportResource注解可以導入xml配置文件。
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);
}
}
解析@Bean方法
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
將@Bean方法轉化為BeanMethod對象，添加到ConfigurationClass#beanMethods集合中。
如果有父類，則解析父類
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();
}
}
如果有父類則返回父類Class對象，繼續調用該方法。直到返回null，外層循環結束。
do {
// 真正的做解析
sourceClass = doProcessConfigurationClass(configClass, sourceClass);
}
while (sourceClass != null);
源碼學習筆記：https://github.com/shenjianeng/spring-code-study
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