SpringIOC源码分析(六)__IOC容器的初始化__BeanDefinition载入注册

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一、前情提要

上一篇提到了IOC容器初始化的流程，及资源定位，本篇主要分析BeanDefinition的载入过程

二、BeanDefiniton载入解析

BeanDefinition是IOC容器对Bean的数据承载模型，IOC容器对Bean的管理和依赖注入的实现，是通过对BeanDefinition的各种操作来实现的，IOC容器通过一个HashMap来保持和维护这些BeanDefinition数据。

时序图：

核心流程：

1. 创建DefaultListableBeanFactory容器
2. 读XML文件解析出Document
3. BeanDefinitionParserDelegate解析Document每个节点的元素，生成BeanDefinitionHolder，BeanDefinitionHolder是BeanDefinition对象的封装累，封装了BeanDefinition，Bean的名字和别名，用它来完成IOC容器注册

解析元素生成BeanDefinitionHolder，并向IOC容器注册BeanDefinition

三、BeanDefiniton注册

定义了hashMap来承载这些Bean

	/** Map of bean definition objects, keyed by bean name */private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);

@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;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);}if (oldBeanDefinition != null || containsSingleton(beanName)) {resetBeanDefinition(beanName);}}

 

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