Spring框架核心源代码的分析及其感受-4
好了！这里又出现了新的类型BeanDefinitionParserDelegate干什么用的？不过我知道这肯定和XML解析有关，所以不容错过！于是乎，简单浏览了一下它的实现（怕进入代码丛林！），我的天啊，我找到正题了：
public class BeanDefinitionParserDelegate {
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??? public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans";
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??? public static final String BEAN_NAME_DELIMITERS = ",; ";
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??? public static final String TRUE_VALUE = "true";
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??? public static final String FALSE_VALUE = "false";
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??? public static final String DEFAULT_VALUE = "default";
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??? public static final String DESCRIPTION_ELEMENT = "description";
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??? public static final String AUTOWIRE_NO_VALUE = "no";
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??? public static final String AUTOWIRE_BY_NAME_VALUE = "byName";
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??? public static final String AUTOWIRE_BY_TYPE_VALUE = "byType";
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??? public static final String AUTOWIRE_CONSTRUCTOR_VALUE = "constructor";
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??? public static final String AUTOWIRE_AUTODETECT_VALUE = "autodetect";
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??? public static final String DEPENDENCY_CHECK_ALL_ATTRIBUTE_VALUE = "all";
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??? public static final String DEPENDENCY_CHECK_SIMPLE_ATTRIBUTE_VALUE = "simple";
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??? public static final String DEPENDENCY_CHECK_OBJECTS_ATTRIBUTE_VALUE = "objects";
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??? public static final String NAME_ATTRIBUTE = "name";
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这不是我们在Spring XML配置文件中经常看到的XML属性名称吗！我又看看了下面一些方法！
protected void populateDefaults(DocumentDefaultsDefinition defaults, DocumentDefaultsDefinition parentDefaults, Element root) {
?????? String lazyInit = root.getAttribute(DEFAULT_LAZY_INIT_ATTRIBUTE);
?????? if (DEFAULT_VALUE.equals(lazyInit)) {
?????????? lazyInit = parentDefaults != null ? parentDefaults.getLazyInit() : FALSE_VALUE;
?????? }
?????? defaults.setLazyInit(lazyInit);
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?????? String merge = root.getAttribute(DEFAULT_MERGE_ATTRIBUTE);
?????? if (DEFAULT_VALUE.equals(merge)) {
?????????? merge = parentDefaults != null ? parentDefaults.getMerge() : FALSE_VALUE;
?????? }
?????? defaults.setMerge(merge);
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?????? String autowire = root.getAttribute(DEFAULT_AUTOWIRE_ATTRIBUTE);
?????? if (DEFAULT_VALUE.equals(autowire)) {
?????????? autowire = parentDefaults != null ? parentDefaults.getAutowire() : AUTOWIRE_NO_VALUE;
?????? }
?????? defaults.setAutowire(autowire);
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?????? defaults.setDependencyCheck(root.getAttribute(DEFAULT_DEPENDENCY_CHECK_ATTRIBUTE));
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?????? if (root.hasAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE)) {
?????? ??? defaults.setAutowireCandidates(root.getAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE));
?????? } else if (parentDefaults != null) {
?????????? defaults.setAutowireCandidates(parentDefaults.getAutowireCandidates());
?????? }
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?????? if (root.hasAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE)) {
?????????? defaults.setInitMethod(root.getAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE));
?????? } else if (parentDefaults != null) {
?????? ??? defaults.setInitMethod(parentDefaults.getInitMethod());
?????? }
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?????? if (root.hasAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE)) {
?????????? defaults.setDestroyMethod(root.getAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE));
?????? } else if (parentDefaults != null) {
?????????? defaults.setDestroyMethod(parentDefaults.getDestroyMethod());
?????? }
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?????? defaults.setSource(this.readerContext.extractSource(root));
??? }
这不就是解析的过程吗？咦？装入BeanDefinition中的逻辑在什么地方，我们不能在Spring代码其他地方直接使用这些配置信息啊，只能给它们包装到一个实体类啊（当数据结构过长，一般是用实体类来存储的，哈哈，我也明白BeanDefinitio的设计目的了！）我继续在这个类里面找：
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
?????? String id = ele.getAttribute(ID_ATTRIBUTE);
?????? String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
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?????? List<String> aliases = new ArrayList<String>();
?????? if (StringUtils.hasLength(nameAttr)) {
?????????? String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, BEAN_NAME_DELIMITERS);
?????????? aliases.addAll(Arrays.asList(nameArr));
?????????? //别名的解析
?????? }
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?????? String beanName = id;
?????? if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
?????????? beanName = aliases.remove(0);//第一个作为Bean的默认名称,very good!
?????????? if (logger.isDebugEnabled()) {
????????????? logger.debug("No XML 'id' specified - using '" + beanName +
???????????????????? "' as bean name and " + aliases + " as aliases");
?????????? }
?????? }
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?????? if (containingBean == null) {
?????????? //check bean名是不是在容器中唯一
?????????? checkNameUniqueness(beanName, aliases, ele);
?????? }
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?????? //在这里具体创建beanDefinition实例，非常好的逻辑，代码逻辑清晰
?????? AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
?????? if (beanDefinition != null) {
?????????? if (!StringUtils.hasText(beanName)) {
????????????? try {
????????????????? if (containingBean != null) {
???????????????????? //没有Bean名的话，就生成一个,.供内部使用
???????????????????? beanName = BeanDefinitionReaderUtils.generateBeanName(
??????????????????????????? beanDefinition, this.readerContext
