spring技术内幕笔记：IoC容器的初始化过程（3）- BeanDefinition的注册

Spring版本：4.3.8.RELEASE

DefaultListableBeanFactory中，通过一个HashMap来持有和载入BeanDefinition，解析得到的BeanDefinition向IoC容器的beanDefinitionMap注册过程

是在载入BeanDefinition完成后进行的。
在DefaultListableBeanFactory中实现了BeanDefinitionRegistry接口，这个接口的实现完成BeanDefinition向容器的注册，这个过程就是把解析得到的BeanDefinition设置到hashMap中，进行BeanDefinition的注册。

@SuppressWarnings("serial")public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactoryimplements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {/** bean definition对象的Map集合，key为bean的name*/private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(256);    /**     * 注册BeanDefinition的过程    */@Overridepublic 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;//检查是不是有相同名字的BeanDefinition已经在IoC容器中注册了，如果有相同的BeanDefinition，但又不允许覆盖，会抛出异常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_INFRASTRUCTUREif (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()) {// 使用synchronized保持数据的一致性synchronized (this.beanDefinitionMap) {this.beanDefinitionMap.put(beanName, beanDefinition);List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);updatedDefinitions.addAll(this.beanDefinitionNames);updatedDefinitions.add(beanName);this.beanDefinitionNames = updatedDefinitions;if (this.manualSingletonNames.contains(beanName)) {Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);updatedSingletons.remove(beanName);this.manualSingletonNames = updatedSingletons;}}}else {// 注册BeanDefinition，将解析后BeanDefinition放入map，key为bean name，value为BeanDefinition对象this.beanDefinitionMap.put(beanName, beanDefinition);this.beanDefinitionNames.add(beanName);this.manualSingletonNames.remove(beanName);}this.frozenBeanDefinitionNames = null;}if (oldBeanDefinition != null || containsSingleton(beanName)) {resetBeanDefinition(beanName);}}}