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;
    }