以下文章来源于SpringForAll社区，作者Darren Luo
由于该篇文章较多，所以就拆分为了上下两篇，接上面完成了beanFactory的信息处理，接下来是bean的相关定义的处理。
1、BEANDEFINITION
获取完beanFactory的之后，代码涉及到了一些bean的定义，接下来看beanDefination的定义。
1、BeanDefinition 设计bean相关信息
2、BeanDefinitionHolder 封装bean定义相关信息，以及bean名称、别名等
3、BeanDefinitionRegistry 持有所有注册的bean相关信息
下面我们接着上面一篇 registerAnnotationConfigProcessors()方法的分析。
代码语言：javascript复制 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));
}这段代码以及其紧跟的代码为创建若干bean，其中
代码语言：javascript复制registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)表示注册名称为 org.springframework.context.annotation.internalConfigurationAnnotationProcessor，beanClass对应为ConfigurationClassPostProcessor的bean
2、BEAN注册
代码语言：javascript复制 private static BeanDefinitionHolder registerPostProcessor(
BeanDefinitionRegistry registry, RootBeanDefinition definition, String beanName) {
definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
registry.registerBeanDefinition(beanName, definition);
return new BeanDefinitionHolder(definition, beanName);
}其中 registry.registerBeanDefinition(beanName,definition)调用GenericApplicationContext中的方法
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
this.beanFactory.registerBeanDefinition(beanName, beanDefinition);
}其中this.beanFactory为DefaultListableBeanFactory实例
代码语言：javascript复制 @Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
BeanDefinition oldBeanDefinition;
oldBeanDefinition = this.beanDefinitionMap.get(beanName);
if (oldBeanDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" beanDefinition "] for bean '" beanName
"': There is already [" oldBeanDefinition "] bound.");
}
else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (this.logger.isWarnEnabled()) {
this.logger.warn("Overriding user-defined bean definition for bean '" beanName
"' with a framework-generated bean definition: replacing ["
oldBeanDefinition "] with [" beanDefinition "]");
}
}
else if (!beanDefinition.equals(oldBeanDefinition)) {
if (this.logger.isInfoEnabled()) {
this.logger.info("Overriding bean definition for bean '" beanName
"' with a different definition: replacing [" oldBeanDefinition
"] with [" beanDefinition "]");
}
}
else {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Overriding bean definition for bean '" beanName
"' with an equivalent definition: replacing [" oldBeanDefinition
"] with [" beanDefinition "]");
}
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// Still in startup registration phase
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (oldBeanDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}以上方法完成了bean的注册；1、首先完成校验
代码语言：javascript复制((AbstractBeanDefinition) beanDefinition).validate()2、接下来从map中获取bean，首次获取肯定是空
代码语言：javascript复制oldBeanDefinition = this.beanDefinitionMap.get(beanName);3、为空进入以下代码
代码语言：javascript复制 if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// Still in startup registration phase
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;这里顺便解释下，在从map中获取到bean时表示bean已经注册，则会判断是否可以覆盖oldBean，也需要判断bean对应的Role级别
以上完成了AnnotationConfigEmbeddedWebApplicationContext中 AnnotatedBeanDefinitionReader实例的构造
接下来为ClassPathBeanDefinitionScanner实例的创建
代码语言：javascript复制 public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters) {
this(registry, useDefaultFilters, getOrCreateEnvironment(registry));
}调用内部方法
代码语言：javascript复制 public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters,
Environment environment, @Nullable ResourceLoader resourceLoader) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
this.registry = registry;
if (useDefaultFilters) {
//注册默认拦截器，将Component、ManagedBean、Named注解增加到包含过滤规则中。
registerDefaultFilters();
}
setEnvironment(environment);
//完成对resourcePatternResolver以及metadataReaderFactory的赋值操作。
setResourceLoader(resourceLoader);
}调用super构造
代码语言：javascript复制 public ClassPathScanningCandidateComponentProvider(boolean useDefaultFilters, Environment environment) {
if (useDefaultFilters) {
registerDefaultFilters();
}
Assert.notNull(environment, "Environment must not be null");
this.environment = environment;
}在该方法中完成了environment的赋值以及为ClassPathScanningCandidateComponentProvider完成了默认过滤器的注册
代码语言：javascript复制 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.debug("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.debug("JSR-330 'javax.inject.Named' annotation found and supported for component scanning");
}
catch (ClassNotFoundException ex) {
// JSR-330 API not available - simply skip.
}
}将Component、ManagedBean、Named注解增加到包含过滤规则中。
代码语言：javascript复制 setResourceLoader((ResourceLoader) this.registry)
public void setResourceLoader(@Nullable ResourceLoader resourceLoader) {
this.resourcePatternResolver = ResourcePatternUtils.getResourcePatternResolver(resourceLoader);
this.metadataReaderFactory = new CachingMetadataReaderFactory(resourceLoader);
this.componentsIndex = CandidateComponentsIndexLoader.loadIndex(this.resourcePatternResolver.getClassLoader());
}完成对resourcePatternResolver以及metadataReaderFactory的赋值操作。至此，完成了对上下文的创建
