深入理解ClassPathBeanDefinitionScanner
1 介绍
ClassPathBeanDefinitionScanner可以扫描指定路径下的@Component类，将这些类解析成BeanDefinition，注册到Spring容器中。
此外，ClassPathBeanDefinitionScanner通过注册相关注解后处理器，提供了对@Order、@Priority、@Autowired、@Configuration和@EventListener等注解的支持。
ClassPathScanningCandidateComponentProvider成员变量：
resourcePattern：资源文件的路径匹配模式，默认是**/*.class，表示会扫描所有类文件。includeFilters：过滤器，满足条件的类会被注册成bean。默认条件为标注@Component、@ManagedBean或@Named注解，后两个条件成立需要引入相关依赖。excludeFilters：过滤器，满足条件的类会被跳过，不会被注册成bean。默认为空。environment：运行时环境，可获取系统变量和配置文件信息。conditionEvaluator：会根据@Conditional注解判断是否需要注册成bean。resourcePatternResolver：根据路径匹配模式获取类文件的Resource对象数组。metadataReaderFactory：MetadataReader工厂，用来读取类文件的元数据。componentsIndex：
ClassPathBeanDefinitionScanner成员变量：
registry：BeanDefinition注册器，实际上就是Spring容器。beanDefinitionDefaults：BeanDefinition默认属性的封装工具。autowireCandidatePatterns：beanNameGenerator：beanName生成器，会先获取@Component、@ManagedBean、@Named或@Component子注解的value属性，没有再按类名生成。scopeMetadataResolver：作用域解析器，会先获取@Scope注解的value和proxyMode属性，没有则使用默认值（singleton和ScopedProxyMode.NO）。includeAnnotationConfig：是否往Spring容器注册默认的XxxProcessor，默认为true。
2 基本使用
在使用ClassPathBeanDefinitionScanner时，首先需要为其设置registry属性，通常通过构造函数进行设置。
DefaultListableBeanFactory和GenericApplicationContext都实现了BeandefinitionRegistry接口，Spring容器实现类基本上都可以作为registry设置到ClassPathBeanDefinitionScanner中。
然后，通过ClassPathBeanDefinitionScanner#scan()就可以扫描指定包下的所有类文件，将符合条件的类作为BeanDefinition，注册到registry中。
以下是使用ClassPathBeanDefinitionScanner扫描指定包下所有bean的最基本使用：
// 创建registry
BeanDefinitionRegistry registry = new DefaultListableBeanFactory();
// 创建scanner，设置registry
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(registry);
// 扫描指定包下的bean
scanner.scan("com.example.component");
// 获取bean
BeanFactory beanFactory = (BeanFactory) registry;
Object bean = beanFactory.getBean("xxx");
3 源码解读
3.1 构造函数初始化
我们通常会使用ClassPathBeanDefinitionScanner(BeanDefinitionRegistry)构造函数进行初始化，为其指定registry属性：
public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry) {
this(registry, true);
}
在这个过程中，除了registry，还会初始化includeFilters、environment、resourcePatternResolver、metadataReaderFactory和componentsIndex等属性：
public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters,
Environment environment, @Nullable ResourceLoader resourceLoader) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
// 初始化registry
this.registry = registry;
// 初始化includeFilters：添加@Component、@ManagedBean和@Named条件
if (useDefaultFilters) {
registerDefaultFilters();
}
// 初始化environment
setEnvironment(environment);
// 初始化resourcePatternResolver、metadataReaderFactory和componentsIndex
setResourceLoader(resourceLoader);
}
在ClassPathScanningCandidateComponentProvider#registerDefaultFilters()方法中，会添加校验@Component、@ManagedBean和@Named三个条件的注解过滤器。需要注意的是，后两个过滤器只有在引入相关依赖的时候才会生效：
protected void registerDefaultFilters() {
this.includeFilters.add(new AnnotationTypeFilter(Component.class));
ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader();
try {
this.includeFilters.add(new AnnotationTypeFilter(
((Class<? extends Annotation>) ClassUtils.forName("javax.annotation.ManagedBean", cl)), false));
logger.trace("JSR-250 'javax.annotation.ManagedBean' found and supported for component scanning");
}
catch (ClassNotFoundException ex) {
// JSR-250 1.1 API (as included in Java EE 6) not available - simply skip.
}
try {
this.includeFilters.add(new AnnotationTypeFilter(
((Class<? extends Annotation>) ClassUtils.forName("javax.inject.Named", cl)), false));
logger.trace("JSR-330 'javax.inject.Named' annotation found and supported for component scanning");
}
catch (ClassNotFoundException ex) {
// JSR-330 API not available - simply skip.
}
}
在ClassPathScanningCandidateComponentProvider#setResourceLoader()方法中，会初始化resourcePatternResolver、metadataReaderFactory和componentsIndex：
public void setResourceLoader(@Nullable ResourceLoader resourceLoader) {
this.resourcePatternResolver = ResourcePatternUtils.getResourcePatternResolver(resourceLoader);
this.metadataReaderFactory = new CachingMetadataReaderFactory(resourceLoader);
this.componentsIndex = CandidateComponentsIndexLoader.loadIndex(this.resourcePatternResolver.getClassLoader());
}
在初始化resourcePatternResolver时，会判断registry是否是ResourcePatternResolver实现类（因为ApplicationContext继承了ResourcePatternResolver接口，而DefaultListableBeanFactory则没有）。如果是，直接将registry赋值给resourcePatternResolver；如果不是，则会新建一个PathMatchingResourcePatternResolver对象：
public static ResourcePatternResolver getResourcePatternResolver(@Nullable ResourceLoader resourceLoader) {
if (resourceLoader instanceof ResourcePatternResolver) {
return (ResourcePatternResolver) resourceLoader;
}
else if (resourceLoader != null) {
return new PathMatchingResourcePatternResolver(resourceLoader);
}
else {
return new PathMatchingResourcePatternResolver();
}
}
在初始化componentsIndex时，会尝试读取META-INF/spring.components文件中定义的配置信息，后续扫描时会从配置信息里获取符合条件的bean进行加载：
private static CandidateComponentsIndex doLoadIndex(ClassLoader classLoader) {
// 读取spring.index.ignore配置，需要关闭spring.components功能时可以将设为false
if (shouldIgnoreIndex) {
return null;
}
try {
// 读取META-INF/spring.components
Enumeration<URL> urls = classLoader.getResources(COMPONENTS_RESOURCE_LOCATION);
if (!urls.hasMoreElements()) {
return null;
}
// 获取配置
List<Properties> result = new ArrayList<>();
while (urls.hasMoreElements()) {
URL url = urls.nextElement();
Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));
result.add(properties);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + result.size() + " index(es)");
}
int totalCount = result.stream().mapToInt(Properties::size).sum();
return (totalCount > 0 ? new CandidateComponentsIndex(result) : null);
}
catch (IOException ex) {
throw new IllegalStateException("Unable to load indexes from location [" +
COMPONENTS_RESOURCE_LOCATION + "]", ex);
}
}
META-INF/spring.components文件格式如下：
全限定类名1=注解全限定类名1,注解全限定类名2
全限定类名2=注解全限定类名1
需要特别注意的是，开启spring.components还需要includeFilters中仅支持@Indexed及其子注解的条件过滤器，如果初始化了componentsIndex，后续扫描时只会在META-INF/spring.components文件中筛选路径匹配的类进行注册。如果遇到包下的bean扫描不到时，可以从这方面考虑。
3.2 扫描
3.2.1 scan
通过ClassPathBeanDefinitionScanner#scan()方法可以扫描指定包，注册XxxProcessor，并且计算本次注册bean的数量：
public int scan(String... basePackages) {
int beanCountAtScanStart = this.registry.getBeanDefinitionCount();
// 实际扫描方法
doScan(basePackages);
// 注册XxxProcessor
if (this.includeAnnotationConfig) {
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
return (this.registry.getBeanDefinitionCount() - beanCountAtScanStart);
}
3.2.2 doScan
ClassPathBeanDefinitionScanner#doScan()方法是扫描的核心方法，它会扫描指定包，设置BeanDefinition的基本属性，最后注册到registry中：
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
// 遍历basePackages
for (String basePackage : basePackages) {
// 从指定basePackage中筛选满足条件的类，解析成BeanDefinition
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
// 遍历candidates，设置基本属性
for (BeanDefinition candidate : candidates) {
// 设置作用域：读取@Scope属性进行设置
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
// 设置beanName：读取@Component属性，或者根据类名生成
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
// 设置AbstractBeanDefinition相关基本属性
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
// 设置AnnotatedBeanDefinition相关基本属性
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
// 校验是否重复注册&注册到Spring容器
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;
}
findCandidateComponents
ClassPathScanningCandidateComponentProvider#findCandidateComponents()包含扫描包的核心代码。
如果开启了spring.components配置，并且includeFilters中只有@Indexed及其子注解条件（或者注解全限定类名以javax.开头），就会从spring.components中扫描满足条件的类进行解析。
如果没有开启spring.component配置，或者includeFilters不满足条件，就会从类路径中扫描满足条件的类进行解析。
ClassPathScanningCandidateComponentProvider#findCandidateComponents()源码如下：
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
// 开启spring.components配置，并且includeFilters过滤器仅支持@Indexed及其子注解条件时：从配置中扫描
if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
}
// 从指定包中扫描
else {
return scanCandidateComponents(basePackage);
}
}
扫描spring.components
我们先来看ClassPathScanningCandidateComponentProvider#addCandidateComponentsFromIndex()方法，它会从spring.components中获取满足条件的全限定类名，然后读取对应类文件，最后构建成BeanDefinition对象：
private Set<BeanDefinition> addCandidateComponentsFromIndex(CandidateComponentsIndex index, String basePackage) {
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
// 根据includeFilters中的条件和basePackage从spring.components中获取对应类
Set<String> types = new HashSet<>();
for (TypeFilter filter : this.includeFilters) {
// stereotype是注解全限定类名，如org.springframework.stereotype.Component
String stereotype = extractStereotype(filter);
if (stereotype == null) {
throw new IllegalArgumentException("Failed to extract stereotype from " + filter);
}
// 根据basePackage和stereotype，从spring.components中获取对应类
types.addAll(index.getCandidateTypes(basePackage, stereotype));
}
// 遍历所有类
for (String type : types) {
// 获取元数据
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(type);
// 校验是否满足excludeFilters和includeFilters条件（注意校验顺序）
if (isCandidateComponent(metadataReader)) {
// 解析成BeanDefinition，设置基本属性
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setSource(metadataReader.getResource());
// 校验BeanDefinition是否满足条件：比如是否可以进行初始化
if (isCandidateComponent(sbd)) {
candidates.add(sbd);
}
}
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
}
return candidates;
}
CandidateComponentsIndex#getCandidateTypes()方法定义了从spring.components扫描的逻辑：
public Set<String> getCandidateTypes(String basePackage, String stereotype) {
// 获取符合注解条件的所有候补类
List<Entry> candidates = this.index.get(stereotype);
if (candidates != null) {
// 过滤出满足包条件的所有类
return candidates.parallelStream()
.filter(t -> t.match(basePackage))
.map(t -> t.type)
.collect(Collectors.toSet());
}
return Collections.emptySet();
}
SimpleMetadataReaderFactory#getMetadataReader()会使用resourceLoader读取类文件（涉及到Resource相关知识，可以查看Spring的Resource体系介绍），然后解析类文件的注解信息：
public MetadataReader getMetadataReader(String className) throws IOException {
try {
// 类文件路径：classpath:全限定类名.class
String resourcePath = ResourceLoader.CLASSPATH_URL_PREFIX +
ClassUtils.convertClassNameToResourcePath(className) + ClassUtils.CLASS_FILE_SUFFIX;
// 获取类文件的ClassPathResource对象
Resource resource = this.resourceLoader.getResource(resourcePath);
// 读取元数据
return getMetadataReader(resource);
}
catch (FileNotFoundException ex) {
}
}
SimpleMetadataReaderFactory#getMetadataReader()方法实际上会创建一个SimpleMetadataReader对象，在它的构造函数中会解析注解元数据。解析过程会使用ASM操作Java字节码，这里不进行过多介绍（还没研究过）：
SimpleMetadataReader(Resource resource, @Nullable ClassLoader classLoader) throws IOException {
SimpleAnnotationMetadataReadingVisitor visitor = new SimpleAnnotationMetadataReadingVisitor(classLoader);
// 解析注解元数据：调用ClassReader#accept()方法
getClassReader(resource).accept(visitor, PARSING_OPTIONS);
this.resource = resource;
this.annotationMetadata = visitor.getMetadata();
}
回到ClassPathScanningCandidateComponentProvider#addCandidateComponentsFromIndex()方法，接下来会调用ClassPathScanningCandidateComponentProvider#isCandidateComponent()方法进行过滤：
- 按
excludeFilters条件过滤（默认是空）。 - 按
includeFilters条件过滤（默认是@Component）。 - 按
@Conditional条件过滤（参考深入理解AnnotatedBeanDefinitionReader）。
ClassPathScanningCandidateComponentProvider#isCandidateComponent()方法如下：
protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
// 按excludeFilters条件过滤（默认是空）
for (TypeFilter tf : this.excludeFilters) {
if (tf.match(metadataReader, getMetadataReaderFactory())) {
return false;
}
}
// 按includeFilters条件过滤（默认是@Component）
for (TypeFilter tf : this.includeFilters) {
if (tf.match(metadataReader, getMetadataReaderFactory())) {
// 按@Conditional条件过滤
return isConditionMatch(metadataReader);
}
}
return false;
}
接下来，会创建ScannedGenericBeanDefinition对象，设置好相关基本信息。然后还会对ScannedGenericBeanDefinition对象进行一次判断，这次主要是校验这个bean能否成功初始化：
protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
AnnotationMetadata metadata = beanDefinition.getMetadata();
return (metadata.isIndependent() && (metadata.isConcrete() ||
(metadata.isAbstract() && metadata.hasAnnotatedMethods(Lookup.class.getName()))));
}
扫描类路径
ClassPathScanningCandidateComponentProvider#scanCandidateComponents()方法会扫描类路径下所有满足条件的类。它的操作与扫描spring.components配置一致，只是类文件来源不同：
private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
// 类文件路径匹配规则：classpath*:包路径/**/*.class
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + '/' + this.resourcePattern;
// 加载包路径下所有类文件
Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
// 遍历所有类文件
for (Resource resource : resources) {
try {
// 读取元数据
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
// 校验是否满足excludeFilters和includeFilters条件（注意校验顺序）
if (isCandidateComponent(metadataReader)) {
// 解析成BeanDefinition，设置基本属性
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setSource(resource);
// 校验BeanDefinition是否满足条件：比如是否可以进行初始化
if (isCandidateComponent(sbd)) {
candidates.add(sbd);
}
}
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to read candidate component class: " + resource, ex);
}
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
}
return candidates;
}
注册Beandefinition
回到ClassPathBeanDefinitionScanner#doScan()方法，此时我们已经得到了BeanDefinition对象。接下来会进行设置作用域、beanName等基本属性，可以参考深入理解AnnotatedBeanDefinitionReader。
3.2.3 registerAnnotationConfigProcessors
回到ClassPathBeanDefinitionScanner#scan()方法，在扫描并注册完指定路径下的类后，还会注册XxxProcessor：
// 默认为true
if (this.includeAnnotationConfig) {
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
在AnnotationConfigUtils#registerAnnotationConfigProcessors()方法中，会添加许多后处理器：
ConfigurationClassPostProcessor：处理@Configuration。AutowiredAnnotationBeanPostProcessor：处理@Autowired和@Value。CommonAnnotationBeanPostProcessor：提供对JSR-250的支持。internalPersistenceAnnotationProcessor：提供对JPA的支持。EventListenerMethodProcessor和DefaultEventListenerFactory：处理@EventListener。
AnnotationConfigUtils#registerAnnotationConfigProcessors()方法如下：
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
BeanDefinitionRegistry registry, @Nullable Object source) {
DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
if (beanFactory != null) {
// 添加对@Order的支持
if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
}
// 添加对@Qualifier和@Value的支持
if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
}
}
Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);
// 添加ConfigurationClassPostProcessor后处理器：@Configuration
if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// 添加AutowiredAnnotationBeanPostProcessor后处理器：@Autowired和@Value
if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// 添加CommonAnnotationBeanPostProcessor后处理器：@PostConstruct、@PreDestroy、@Resource等
if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// 添加PersistenceAnnotationBeanPostProcessor后处理器：支持JPA功能
if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition();
try {
def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
AnnotationConfigUtils.class.getClassLoader()));
}
catch (ClassNotFoundException ex) {
throw new IllegalStateException(
"Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
}
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// 添加EventListenerMethodProcessor后处理器：@EventListener
if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
}
// 添加DefaultEventListenerFactory后处理器：@EventListener
if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
}
return beanDefs;
}
关于后处理器的执行原理，会在后续的文章中详细介绍。
4 典型案例
4.1 DefaultListableBeanFactory
在使用DefaultListableBeanFactory时，可以用ClassPathBeanDefinitionScanner为其注册bean，这也是最基础的用法：
// 创建registry
BeanDefinitionRegistry registry = new DefaultListableBeanFactory();
// 创建scanner，设置registry
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(registry);
// 扫描指定包下的bean
scanner.scan("com.example.component");
// 获取bean
BeanFactory beanFactory = (BeanFactory) registry;
Object bean = beanFactory.getBean("");
4.2 AnnotationConfigApplicationContext
在使用AnnotationConfigApplicationContext时，它内部会调用ClassPathBeanDefinitionScanner成员变量进行注册bean：
ApplicationContext context = new AnnotationConfigApplicationContext("com.example.component");
其他AnnotationConfigApplicationContext、AnnotationConfigWebApplicationContext、AnnotationConfigServletWebApplicationContext和AnnotationConfigReactiveWebServerApplicationContext等ApplicationContext实现类也会使用这种方式进行扫描。
4.3 @ComponentScan
@ComponentScan底层会调用ClassPathBeanDefinitionScanner进行注册bean，ComponentScanAnnotationParser#parse()：
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, 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 includeFilterAttributes : componentScan.getAnnotationArray("includeFilters")) {
List<TypeFilter> typeFilters = TypeFilterUtils.createTypeFiltersFor(includeFilterAttributes, this.environment,
this.resourceLoader, this.registry);
for (TypeFilter typeFilter : typeFilters) {
scanner.addIncludeFilter(typeFilter);
}
}
for (AnnotationAttributes excludeFilterAttributes : componentScan.getAnnotationArray("excludeFilters")) {
List<TypeFilter> typeFilters = TypeFilterUtils.createTypeFiltersFor(excludeFilterAttributes, this.environment,
this.resourceLoader, this.registry);
for (TypeFilter typeFilter : typeFilters) {
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));
}
4.4 context:component-scan/
<context:component-scan/>也会使用ClassPathBeanDefinitionScanner进行注册bean，ComponentScanBeanDefinitionParser#parse()：
public BeanDefinition parse(Element element, ParserContext parserContext) {
String basePackage = element.getAttribute(BASE_PACKAGE_ATTRIBUTE);
basePackage = parserContext.getReaderContext().getEnvironment().resolvePlaceholders(basePackage);
String[] basePackages = StringUtils.tokenizeToStringArray(basePackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
// Actually scan for bean definitions and register them.
ClassPathBeanDefinitionScanner scanner = configureScanner(parserContext, element);
Set<BeanDefinitionHolder> beanDefinitions = scanner.doScan(basePackages);
registerComponents(parserContext.getReaderContext(), beanDefinitions, element);
return null;
}
4.5 ClassPathMapperScanner
Mybatis的ClassPathMapperScanner继承了ClassPathBeanDefinitionScanner，@MapperScan使用它来注册bean。
`org.mybatis.spring.mapper.MapperScannerConfigurer#postProcessBeanDefinitionRegistry()：
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
if (this.processPropertyPlaceHolders) {
processPropertyPlaceHolders();
}
ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
scanner.setAddToConfig(this.addToConfig);
scanner.setAnnotationClass(this.annotationClass);
scanner.setMarkerInterface(this.markerInterface);
scanner.setSqlSessionFactory(this.sqlSessionFactory);
scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
scanner.setResourceLoader(this.applicationContext);
scanner.setBeanNameGenerator(this.nameGenerator);
scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
if (StringUtils.hasText(lazyInitialization)) {
scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization));
}
if (StringUtils.hasText(defaultScope)) {
scanner.setDefaultScope(defaultScope);
}
scanner.registerFilters();
scanner.scan(
StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
