Spring配置文件解析之BeanDefinitionParserDelegate詳解
更新時(shí)間：2024年02月14日 08:47:16 作者：軍偉@
這篇文章主要介紹了Spring配置文件解析之BeanDefinitionParserDelegate詳解,對(duì)于Spring的配置文件的解析處理操作是在BeanDefinitionParserDelegate中進(jìn)行處理操作,接下來我們簡(jiǎn)單介紹一下BeanDefinitionParserDelegate所做的處理操作,需要的朋友可以參考下
Spring的BeanDefinitionParserDelegate
上一篇Spring配置文件解析之BeanDefinitionDocumentReader詳解中我們已經(jīng)了解到對(duì)于Spring的配置文件的解析處理操作是在BeanDefinitionParserDelegate中進(jìn)行處理操作，接下來我們簡(jiǎn)單介紹一下BeanDefinitionParserDelegate所做的處理操作。
首先BeanDefinitionParserDelegate中定義了其會(huì)解析xml的spring元素標(biāo)簽，并且還有說明一點(diǎn)的是Spring解析xml的標(biāo)簽是通過命名空間Namespace來決定的，BeanDefinitionParserDelegate中定義了如下命名空間，只會(huì)支持解析這個(gè)命名空間中的標(biāo)簽元素。
public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans";
BeanDefinitionParserDelegate中定義的spring的標(biāo)簽元素如下：
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";
接下來我們看一下對(duì)一個(gè)簡(jiǎn)單的bean注入的配置的解析處理操作。
<bean id="transaction" name="transaction" class="com.xxxx.aop.two.Transaction"></bean>
這里需要解析的元素有id，name和class三個(gè)標(biāo)簽，在上面均有定義。
在parseBeanDefinitionElement中會(huì)完成id和name標(biāo)簽的解析處理操作，并最終生成BeanDefinitionHolder返回，class標(biāo)簽的元素解析在parseBeanDefinitionElement中處理
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);
//獲取別名
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);
}
//解析其他元素標(biāo)簽
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);
//最終生成BeanDefinitionHolder
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}
return null;
}接下來我們看看對(duì)class標(biāo)簽的解析處理操作。parseBeanDefinitionElement中會(huì)完成對(duì)class等其他標(biāo)簽的解析處理操作，最終生成BeanDefinition返回。
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
//解析class標(biāo)簽內(nèi)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));
//最終生成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;
}總結(jié)
繞了那么一大圈，Spring配置文件的解析處理操作是在BeanDefinitionParserDelegate中完成，當(dāng)然也是只是完成了對(duì)Beans這個(gè)命名空間中的元素的解析處理操作，對(duì)于其他的命名空間是通過其他解析器進(jìn)行解析操作的，接下來我們會(huì)進(jìn)行分析，BeanDefinitionParserDelegate做的處理操作就是將bean的各種標(biāo)簽解析成BeanDefinition對(duì)象，并組裝成BeanDefinitionHolder返回。
到此這篇關(guān)于Spring配置文件解析之BeanDefinitionParserDelegate詳解的文章就介紹到這了,更多相關(guān)Spring的BeanDefinitionParserDelegate內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！
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