4.3 spring-嵌入式beans标签的解析

　　对于嵌入式的beans标签,想信大家很少使用过,或者接触过,起码,我本人就没用过. 它非常类似于Import标签所提供的功能;

使用如下:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    <beans></beans>
</beans> 

　　对这个beans没什么太多可讲,解析代码如下:

 protected void doRegisterBeanDefinitions(Element root) {
         String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
         // 处理profile属性
         /*
          * this is header...
          *
          * <beans profile = 'dev"></beans>
          *
          * <beans profile = 'production"></beans>
          *
          * web.xml
          *
          * <context-param>
          *
          * <param-name>Spring.profiles.active</param-name>
          *
          * <param-value>dev</param-value>
          *
          * </context-param>
          */
         if (StringUtils.hasText(profileSpec)) {
             Assert.state(this.environment != null,
                     "Environment must be set for evaluating profiles");
             String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec,
                     BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
             if (!this.environment.acceptsProfiles(specifiedProfiles)) {
                 return;
             }
         }

         // Any nested <beans> elements will cause recursion in this method. In
         // order to propagate and preserve <beans> default-* attributes correctly,
         // keep track of the current (parent) delegate, which may be null. Create
         // the new (child) delegate with a reference to the parent for fallback purposes,
         // then ultimately reset this.delegate back to its original (parent) reference.
         // this behavior emulates a stack of delegates without actually necessitating one.
         // 专门处理解析
         BeanDefinitionParserDelegate parent = this.delegate;
         this.delegate = createDelegate(this.readerContext, root, parent);
         // 解析前留给子类实现
         preProcessXml(root);

         parseBeanDefinitions(root, this.delegate);
         // 解析后留给子类实现
         postProcessXml(root);

         this.delegate = parent;
     }