Spring配置文件解析之BeanDefinitionParserDelegate详解
作者：军伟@
这篇文章主要介绍了Spring配置文件解析之BeanDefinitionParserDelegate详解,对于Spring的配置文件的解析处理操作是在BeanDefinitionParserDelegate中进行处理操作,接下来我们简单介绍一下BeanDefinitionParserDelegate所做的处理操作,需要的朋友可以参考下
Spring的BeanDefinitionParserDelegate
上一篇Spring配置文件解析之BeanDefinitionDocumentReader详解中我们已经了解到对于Spring的配置文件的解析处理操作是在BeanDefinitionParserDelegate中进行处理操作，接下来我们简单介绍一下BeanDefinitionParserDelegate所做的处理操作。
首先BeanDefinitionParserDelegate中定义了其会解析xml的spring元素标签，并且还有说明一点的是Spring解析xml的标签是通过命名空间Namespace来决定的，BeanDefinitionParserDelegate中定义了如下命名空间，只会支持解析这个命名空间中的标签元素。
public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans";
BeanDefinitionParserDelegate中定义的spring的标签元素如下：
public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans"; public static final String MULTI_VALUE_ATTRIBUTE_DELIMITERS = ",; "; public static final String TRUE_VALUE = "true"; public static final String FALSE_VALUE = "false"; public static final String DEFAULT_VALUE = "default"; public static final String DESCRIPTION_ELEMENT = "description"; public static final String AUTOWIRE_NO_VALUE = "no"; public static final String AUTOWIRE_BY_NAME_VALUE = "byName"; public static final String AUTOWIRE_BY_TYPE_VALUE = "byType"; public static final String AUTOWIRE_CONSTRUCTOR_VALUE = "constructor"; public static final String AUTOWIRE_AUTODETECT_VALUE = "autodetect"; public static final String DEPENDENCY_CHECK_ALL_ATTRIBUTE_VALUE = "all"; public static final String DEPENDENCY_CHECK_SIMPLE_ATTRIBUTE_VALUE = "simple"; public static final String DEPENDENCY_CHECK_OBJECTS_ATTRIBUTE_VALUE = "objects"; public static final String NAME_ATTRIBUTE = "name"; public static final String BEAN_ELEMENT = "bean"; public static final String META_ELEMENT = "meta"; public static final String ID_ATTRIBUTE = "id"; public static final String PARENT_ATTRIBUTE = "parent"; public static final String CLASS_ATTRIBUTE = "class"; public static final String ABSTRACT_ATTRIBUTE = "abstract"; public static final String SCOPE_ATTRIBUTE = "scope"; private static final String SINGLETON_ATTRIBUTE = "singleton"; public static final String LAZY_INIT_ATTRIBUTE = "lazy-init"; public static final String AUTOWIRE_ATTRIBUTE = "autowire"; public static final String AUTOWIRE_CANDIDATE_ATTRIBUTE = "autowire-candidate"; public static final String PRIMARY_ATTRIBUTE = "primary"; public static final String DEPENDENCY_CHECK_ATTRIBUTE = "dependency-check"; public static final String DEPENDS_ON_ATTRIBUTE = "depends-on"; public static final String INIT_METHOD_ATTRIBUTE = "init-method"; public static final String DESTROY_METHOD_ATTRIBUTE = "destroy-method"; public static final String FACTORY_METHOD_ATTRIBUTE = "factory-method"; public static final String FACTORY_BEAN_ATTRIBUTE = "factory-bean"; public static final String CONSTRUCTOR_ARG_ELEMENT = "constructor-arg"; public static final String INDEX_ATTRIBUTE = "index"; public static final String TYPE_ATTRIBUTE = "type"; public static final String VALUE_TYPE_ATTRIBUTE = "value-type"; public static final String KEY_TYPE_ATTRIBUTE = "key-type"; public static final String PROPERTY_ELEMENT = "property"; public static final String REF_ATTRIBUTE = "ref"; public static final String VALUE_ATTRIBUTE = "value"; public static final String LOOKUP_METHOD_ELEMENT = "lookup-method"; public static final String REPLACED_METHOD_ELEMENT = "replaced-method"; public static final String REPLACER_ATTRIBUTE = "replacer"; public static final String ARG_TYPE_ELEMENT = "arg-type"; public static final String ARG_TYPE_MATCH_ATTRIBUTE = "match"; public static final String REF_ELEMENT = "ref"; public static final String IDREF_ELEMENT = "idref"; public static final String BEAN_REF_ATTRIBUTE = "bean"; public static final String LOCAL_REF_ATTRIBUTE = "local"; public static final String PARENT_REF_ATTRIBUTE = "parent"; public static final String VALUE_ELEMENT = "value"; public static final String NULL_ELEMENT = "null"; public static final String ARRAY_ELEMENT = "array"; public static final String LIST_ELEMENT = "list"; public static final String SET_ELEMENT = "set"; public static final String MAP_ELEMENT = "map"; public static final String ENTRY_ELEMENT = "entry"; public static final String KEY_ELEMENT = "key"; public static final String KEY_ATTRIBUTE = "key"; public static final String KEY_REF_ATTRIBUTE = "key-ref"; public static final String VALUE_REF_ATTRIBUTE = "value-ref"; public static final String PROPS_ELEMENT = "props"; public static final String PROP_ELEMENT = "prop"; public static final String MERGE_ATTRIBUTE = "merge"; public static final String QUALIFIER_ELEMENT = "qualifier"; public static final String QUALIFIER_ATTRIBUTE_ELEMENT = "attribute"; public static final String DEFAULT_LAZY_INIT_ATTRIBUTE = "default-lazy-init"; public static final String DEFAULT_MERGE_ATTRIBUTE = "default-merge"; public static final String DEFAULT_AUTOWIRE_ATTRIBUTE = "default-autowire"; public static final String DEFAULT_DEPENDENCY_CHECK_ATTRIBUTE = "default-dependency-check"; public static final String DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE = "default-autowire-candidates"; public static final String DEFAULT_INIT_METHOD_ATTRIBUTE = "default-init-method"; public static final String DEFAULT_DESTROY_METHOD_ATTRIBUTE = "default-destroy-method";
接下来我们看一下对一个简单的bean注入的配置的解析处理操作。
<bean id="transaction" name="transaction" class="com.xxxx.aop.two.Transaction"></bean>
这里需要解析的元素有id，name和class三个标签，在上面均有定义。
在parseBeanDefinitionElement中会完成id和name标签的解析处理操作，并最终生成BeanDefinitionHolder返回，class标签的元素解析在parseBeanDefinitionElement中处理
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
//解析id
String id = ele.getAttribute(ID_ATTRIBUTE);
//解析name
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
//获取别名
List<String> aliases = new ArrayList<String>();
if (StringUtils.hasLength(nameAttr)) {
String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
aliases.addAll(Arrays.asList(nameArr));
}
String beanName = id;
if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
beanName = aliases.remove(0);
if (logger.isDebugEnabled()) {
logger.debug("No XML 'id' specified - using '" + beanName +
"' as bean name and " + aliases + " as aliases");
}
}
if (containingBean == null) {
checkNameUniqueness(beanName, aliases, ele);
}
//解析其他元素标签
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
if (!StringUtils.hasText(beanName)) {
try {
if (containingBean != null) {
beanName = BeanDefinitionReaderUtils.generateBeanName(
beanDefinition, this.readerContext.getRegistry(), true);
}
else {
beanName = this.readerContext.generateBeanName(beanDefinition);
// Register an alias for the plain bean class name, if still possible,
// if the generator returned the class name plus a suffix.
// This is expected for Spring 1.2/2.0 backwards compatibility.
String beanClassName = beanDefinition.getBeanClassName();
if (beanClassName != null &&
beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&
!this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
aliases.add(beanClassName);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Neither XML 'id' nor 'name' specified - " +
"using generated bean name [" + beanName + "]");
}
}
catch (Exception ex) {
error(ex.getMessage(), ele);
return null;
}
}
String[] aliasesArray = StringUtils.toStringArray(aliases);
//最终生成BeanDefinitionHolder
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}
return null;
}接下来我们看看对class标签的解析处理操作。parseBeanDefinitionElement中会完成对class等其他标签的解析处理操作，最终生成BeanDefinition返回。
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
//解析class标签内容
String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
try {
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
parseMetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
parseConstructorArgElements(ele, bd);
parsePropertyElements(ele, bd);
parseQualifierElements(ele, bd);
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
//最终生成BeanDefinition返回
return bd;
}
catch (ClassNotFoundException ex) {
error("Bean class [" + className + "] not found", ele, ex);
}
catch (NoClassDefFoundError err) {
error("Class that bean class [" + className + "] depends on not found", ele, err);
}
catch (Throwable ex) {
error("Unexpected failure during bean definition parsing", ele, ex);
}
finally {
this.parseState.pop();
}
return null;
}总结
绕了那么一大圈，Spring配置文件的解析处理操作是在BeanDefinitionParserDelegate中完成，当然也是只是完成了对Beans这个命名空间中的元素的解析处理操作，对于其他的命名空间是通过其他解析器进行解析操作的，接下来我们会进行分析，BeanDefinitionParserDelegate做的处理操作就是将bean的各种标签解析成BeanDefinition对象，并组装成BeanDefinitionHolder返回。
到此这篇关于Spring配置文件解析之BeanDefinitionParserDelegate详解的文章就介绍到这了,更多相关Spring的BeanDefinitionParserDelegate内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！