4.1 spring-alias 标签的解析;

　　对于之前漫长的,最核心的Bean标签的解析就没什么好讲的了,

首先看看使用方法:

<bean id="car" name="cat0" class="entity.CarFactoryBean">
        <property name="carInfo" value="超级跑车,400,2000000" />
    </bean>
    <alias name="car" alias="cat1,cat2" />
    <alias name="car" alias="cat3,cat4" />

解析过程如下:

     /**
      * Process the given alias element, registering the alias with the registry.
      */
     protected void processAliasRegistration(Element ele) {
         // 获取beanName
         String name = ele.getAttribute(NAME_ATTRIBUTE);
         // 获取alias
         String alias = ele.getAttribute(ALIAS_ATTRIBUTE);
         boolean valid = true;
         if (!StringUtils.hasText(name)) {
             getReaderContext().error("Name must not be empty", ele);
             valid = false;
         }
         if (!StringUtils.hasText(alias)) {
             getReaderContext().error("Alias must not be empty", ele);
             valid = false;
         }
         if (valid) {
             try {
                 // 注册alias
                 getReaderContext().getRegistry().registerAlias(name, alias);
             }
             catch (Exception ex) {
                 getReaderContext().error(
                         "Failed to register alias '" + alias + "' for bean with name '"
                                 + name + "'", ele, ex);
             }
             // 通知别名监听器
             getReaderContext().fireAliasRegistered(name, alias, extractSource(ele));
         }
     }