本文接着上一篇继续分析Spring中BeanPostProcessor和BeanFactoryPostProcessor。实例化ConfigurationClassParser解析配置类，重点介绍parse方法。处理配置类的@PropertySource、@componentScans，Spring自行创建ClassPathBeanDefinitionScanner进行扫描，用ASM技术获取类，设置属性并注册扫描到的bean，后续将处理@Import情况。
接着上一篇bean的BeanPostProcessor和BeanFactoryPostProcessor的 分析
// Detect any custom bean name generation strategy supplied through the enclosing application context
SingletonBeanRegistry sbr = null;
//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
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet) {//是否有自定义的
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
//SingletonBeanRegistry中有id为 org.springframework.context.annotation.internalConfigurationBeanNameGenerator
//如果有则利用他的，否则则是spring默认的
if (generator != null) {
this.componentScanBeanNameGenerator = generator;
this.importBeanNameGenerator = generator;
}
}
}接着往下分析:接下来实例化了一个ConfigurationClassParser 为了解析各个配置类
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
//实例化2个set,candidates用于将之前加入的configCandidates进行去重
//因为可能有多个配置类重复了
//alreadyParsed用于判断是否处理过
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());下面来看一个很重要的方法
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
parser.parse(candidates); public void parse(Set<BeanDefinitionHolder> configCandidates) {
this.deferredImportSelectors = new LinkedList<>();
//根据BeanDefinition 的类型 做不同的处理,一般都会调用ConfigurationClassParser#parse 进行解析
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
//
try {
if (bd instanceof AnnotatedBeanDefinition) {
//解析注解对象，并且把解析出来的bd放到map，但是这里的bd指的是普通的
//何谓不普通的呢？比如@Bean 和各种beanFactoryPostProcessor得到的bean不在这里put
//但是是这里解析，只是不put而已
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);
}
}
//处理延迟加载的importSelect？为什么要延迟加载，估计就是为了延迟吧
processDeferredImportSelectors();
}我们的appconfig会进这两个分支，原因代码注释上有
进入这个parse方法，看看做了一些什么事情
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}
// 处理Imported 的情况
//就是当前这个注解类有没有被别的类import
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 imports.
// 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 {
sourceClass = doProcessConfigurationClass(configClass, sourceClass);
}
while (sourceClass != null);
//一个map，用来存放扫描出来的bean（注意这里的bean不是对象，仅仅bean的信息，因为还没到实例化这一步）
this.configurationClasses.put(configClass, configClass);
}这里面面最重要的一个方法就是
sourceClass = doProcessConfigurationClass(configClass, sourceClass);protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// Recursively process any member (nested) classes first
//处理内部类
processMemberClasses(configClass, sourceClass);
// Process any @PropertySource annotations
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");
}
}
// 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
//扫描普通类=componentScan=com.luban
//这里扫描出来所有@@Component
//并且把扫描的出来的普通bean放到map当中
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
//检查扫描出来的类当中是否还有configuration
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
//检查 todo
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
/**
* 上面的代码就是扫描普通类----@Component
* 并且放到了map当中
*/
// Process any @Import annotations
//处理@Import imports 3种情况
//ImportSelector
//普通类
//ImportBeanDefinitionRegistrar
//这里和内部地柜调用时候的情况不同
/**
* 这里处理的import是需要判断我们的类当中时候有@Import注解
* 如果有这把@Import当中的值拿出来，是一个类
* 比如@Import(xxxxx.class)，那么这里便把xxxxx传进去进行解析
* 在解析的过程中如果发觉是一个importSelector那么就回调selector的方法
* 返回一个字符串（类名），通过这个字符串得到一个类
* 继而在递归调用本方法来处理这个类
*
* 判断一组类是不是imports（3种import）
*
*
*/
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
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;
}拿到我们的appconfig
先处理 @PropertySource（我对这个属性不熟悉，先不介绍这个，来介绍一些我们都熟悉的类）
Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);拿到我们配置类的@componentScans里面的内容：
因为这个@ComponentScan可以配多个，所以需要循环遍历处理
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName()); public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
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);
}
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);
}
});
return scanner.doScan(StringUtils.toStringArray(basePackages));
}看这个方法的第一行
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);所以我们第一篇博客中说的那个AnnotationConfigApplicationContext scanner是没有用的，只是方便程序员在外部调用的
这里我们能够清楚的看到，spring自己new了一个 ClassPathBeanDefinitionScanner
后面又在这个scanner设置了几个属性
比如：includeFilters excludeFilters lazyInit等
然后又拿到我们需要扫描的包
开始执行扫描:
scanner.doScan(StringUtils.toStringArray(basePackages));
/**
* 类路径 Bean 定义扫描器扫描给定包及其子包
* @param basePackages
* @return
*/
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
// 创建一个集合，存放扫描到Bean定义的封装类
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
// 遍历扫描所有给定的包及其子包
for (String basePackage : basePackages) {
//调用父类 ClassPathScanningCandidateComponentProvider 的方法
//扫描给定类路径，获取符合条件的 Bean 定义
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
//遍历扫描到的 Bean
for (BeanDefinition candidate : candidates) {
//获取 Bean 定义类中@Scope 注解的值，即获取 Bean 的作用域
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
//为 Bean 生成名称
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
//如果扫描到的 Bean 不是 Spring 的注解 Bean，则为 Bean 设置默认值，
//设置 Bean 的自动依赖注入装配属性等
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
//如果扫描到的 Bean 是 Spring 的注解 Bean，则处理其通用的 Spring 注解
if (candidate instanceof AnnotatedBeanDefinition) {
//处理注解 Bean 中通用的注解，在分析注解 Bean 定义类读取器时已经分析过
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
//根据 Bean 名称检查指定的 Bean 是否需要在容器中注册，或者在容器中冲突
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
//根据注解中配置的作用域，为 Bean 应用相应的代理模式
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
//向容器注册扫描到的 Bean
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
} //扫描给定类路径，获取符合条件的 Bean 定义
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);这个方法执行完成之后，就能把我们加了@compoent的类都扫描到，底层用的是ASM技术，我把这个方法贴上去，大家自行查看，我对asm也不了解
private Set<BeanDefinition> addCandidateComponentsFromIndex(CandidateComponentsIndex index, String basePackage) {
//创建存储扫描到的类的集合
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
Set<String> types = new HashSet<>();
for (TypeFilter filter : this.includeFilters) {
String stereotype = extractStereotype(filter);
if (stereotype == null) {
throw new IllegalArgumentException("Failed to extract stereotype from " + filter);
}
types.addAll(index.getCandidateTypes(basePackage, stereotype));
}
boolean traceEnabled = logger.isTraceEnabled();
boolean debugEnabled = logger.isDebugEnabled();
for (String type : types) {
//为指定资源获取元数据读取器，元信息读取器通过汇编(ASM)读取资源元信息
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(type);
//如果扫描到的类符合容器配置的过滤规则
if (isCandidateComponent(metadataReader)) {
//通过汇编(ASM)读取资源字节码中的 Bean 定义元信息
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setSource(metadataReader.getResource());
if (isCandidateComponent(sbd)) {
if (debugEnabled) {
logger.debug("Using candidate component class from index: " + type);
}
candidates.add(sbd);
}
else {
if (debugEnabled) {
logger.debug("Ignored because not a concrete top-level class: " + type);
}
}
}
else {
if (traceEnabled) {
logger.trace("Ignored because matching an exclude filter: " + type);
}
}
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
}
return candidates;
}
然后遍历通过asm拿到的类，遍历,详细可以看我代码的注释，基本都可以看懂,我们来分析下这个代码
//设置 Bean 的自动依赖注入装配属性等
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
//如果扫描到的 Bean 是 Spring 的注解 Bean，则处理其通用的 Spring 注解
if (candidate instanceof AnnotatedBeanDefinition) {
//处理注解 Bean 中通用的注解，在分析注解 Bean 定义类读取器时已经分析过
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}先把默认值设置给bd
protected void postProcessBeanDefinition(AbstractBeanDefinition beanDefinition, String beanName) {
beanDefinition.applyDefaults(this.beanDefinitionDefaults);
if (this.autowireCandidatePatterns != null) {
beanDefinition.setAutowireCandidate(PatternMatchUtils.simpleMatch(this.autowireCandidatePatterns, beanName));
}
}
public void applyDefaults(BeanDefinitionDefaults defaults) {
setLazyInit(defaults.isLazyInit());
setAutowireMode(defaults.getAutowireMode());
setDependencyCheck(defaults.getDependencyCheck());
setInitMethodName(defaults.getInitMethodName());
setEnforceInitMethod(false);
setDestroyMethodName(defaults.getDestroyMethodName());
setEnforceDestroyMethod(false);
}
为 AnnotatedBeanDefinition设置类上设置的属性比如lazy，Primary，DependsOn,Role,Description，类上没有设置，就用上一步设置的默认值
static void processCommonDefinitionAnnotations(AnnotatedBeanDefinition abd, AnnotatedTypeMetadata metadata) {
AnnotationAttributes lazy = attributesFor(metadata, Lazy.class);
//如果 Bean 定义中有@Lazy 注解，则将该 Bean 预实例化属性设置为@lazy 注解的值
if (lazy != null) {
abd.setLazyInit(lazy.getBoolean("value"));
}
else if (abd.getMetadata() != metadata) {
lazy = attributesFor(abd.getMetadata(), Lazy.class);
if (lazy != null) {
abd.setLazyInit(lazy.getBoolean("value"));
}
}
//如果 Bean 定义中有@Primary 注解，则为该 Bean 设置为 autowiring 自动依赖注入装配的首选对象
if (metadata.isAnnotated(Primary.class.getName())) {
abd.setPrimary(true);
}
// 如果 Bean 定义中有@ DependsOn 注解，则为该 Bean 设置所依赖的 Bean 名称
//容器将确保在实例化该 Bean 之前首先实例化所依赖的 Bean
AnnotationAttributes dependsOn = attributesFor(metadata, DependsOn.class);
if (dependsOn != null) {
abd.setDependsOn(dependsOn.getStringArray("value"));
}
if (abd instanceof AbstractBeanDefinition) {
AbstractBeanDefinition absBd = (AbstractBeanDefinition) abd;
AnnotationAttributes role = attributesFor(metadata, Role.class);
if (role != null) {
absBd.setRole(role.getNumber("value").intValue());
}
AnnotationAttributes description = attributesFor(metadata, Description.class);
if (description != null) {
absBd.setDescription(description.getString("value"));
}
}
}然后为bean设置相应的代理模式
// 根据作用域为 Bean 应用引用的代理模式
static BeanDefinitionHolder applyScopedProxyMode(
ScopeMetadata metadata, BeanDefinitionHolder definition, BeanDefinitionRegistry registry) {
//获取注解 Bean 定义类中@Scope 注解的 proxyMode 属性值
ScopedProxyMode scopedProxyMode = metadata.getScopedProxyMode();
//如果配置的@Scope 注解的 proxyMode 属性值为 NO，则不应用代理模式
if (scopedProxyMode.equals(ScopedProxyMode.NO)) {
return definition;
}
//获取配置的@Scope 注解的 proxyMode 属性值，如果为 TARGET_CLASS//则返回 true，如果为 INTERFACES，则返回 fals
boolean proxyTargetClass = scopedProxyMode.equals(ScopedProxyMode.TARGET_CLASS);
// 为注册的Bean创建相应模式的代理对象
return ScopedProxyCreator.createScopedProxy(definition, registry, proxyTargetClass);
}
然后向容器注册扫描到的bean
/**
* 将解析的 BeanDefinitionHold 注册到容器
*/
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
// 获取解析的BeanDefinition的名称
String beanName = definitionHolder.getBeanName();
//像ioc容器中注册BeanDefinition
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
// 如果BeanDefinition有别名。像容器注册其别名
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}这个方法执行完毕以后：我们scan就扫描完成，也就是这个方法执行完成org.springframework.context.annotation.ComponentScanAnnotationParser#parse
然后遍历扫描获得的三个bd
接下来处理@Import的情况 详情请看下篇博客分解
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