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));
        }
    }