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BeanDefinitionParserDelegate 源码分析

发表于: 2015-07-09   作者:zhangwei_david   来源:转载   浏览:
摘要:     public class BeanDefinitionParserDelegate { public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans"; public static final String

 

 

public class BeanDefinitionParserDelegate {

	public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans";

	public static final String MULTI_VALUE_ATTRIBUTE_DELIMITERS = ",; ";

	/** @deprecated as of Spring 3.1 in favor of {@link #MULTI_VALUE_ATTRIBUTE_DELIMITERS} */
	public static final String BEAN_NAME_DELIMITERS = 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";

	public 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";


	protected final Log logger = LogFactory.getLog(getClass());

	private final XmlReaderContext readerContext;

	private final DocumentDefaultsDefinition defaults = new DocumentDefaultsDefinition();

	private final ParseState parseState = new ParseState();

	private Environment environment;

	/**
	 *缓存所有已经解析的bean的id以及别名
	 */
	private final Set<String> usedNames = new HashSet<String>();


	/**
	 * 使用给定的XmlReaderContext和Environment创建一个BeanDefinitionParserDelegate实例
	 */
	public BeanDefinitionParserDelegate(XmlReaderContext readerContext, Environment environment) {
		Assert.notNull(readerContext, "XmlReaderContext must not be null");
		Assert.notNull(readerContext, "Environment must not be null");
		this.readerContext = readerContext;
		this.environment = environment;
	}

	
	@Deprecated
	public BeanDefinitionParserDelegate(XmlReaderContext readerContext) {
		this(readerContext, new StandardEnvironment());
	}

	public final XmlReaderContext getReaderContext() {
		return this.readerContext;
	}

	
	public final Environment getEnvironment() {
		return this.environment;
	}


	protected Object extractSource(Element ele) {
		return this.readerContext.extractSource(ele);
	}

	
	protected void error(String message, Node source) {
		this.readerContext.error(message, source, this.parseState.snapshot());
	}

	
	protected void error(String message, Element source) {
		this.readerContext.error(message, source, this.parseState.snapshot());
	}

	
	protected void error(String message, Element source, Throwable cause) {
		this.readerContext.error(message, source, this.parseState.snapshot(), cause);
	}


	/**
	 *初始化默认值
	 */
	public void initDefaults(Element root, BeanDefinitionParserDelegate parent) {
		populateDefaults(this.defaults, (parent != null ? parent.defaults : null), root);
		this.readerContext.fireDefaultsRegistered(this.defaults);
	}

	/**
	 * 初始化默认值
	 */
	public void initDefaults(Element root) {
		initDefaults(root, null);
	}

	/**
	 * 设置defualt数据,
	 */
	protected void populateDefaults(DocumentDefaultsDefinition defaults, DocumentDefaultsDefinition parentDefaults, Element root) {
		//从根节点即<beans>节点中获取default-lazy-init参数
		String lazyInit = root.getAttribute(DEFAULT_LAZY_INIT_ATTRIBUTE);
		//如果lazyInit的值为default,如果parentDefaults不为null则侧其中获取lazyInit,否则设置为false
		if (DEFAULT_VALUE.equals(lazyInit)) {
			lazyInit = parentDefaults != null ? parentDefaults.getLazyInit() : FALSE_VALUE;
		}
		defaults.setLazyInit(lazyInit);
		//获取default-merge属性
		String merge = root.getAttribute(DEFAULT_MERGE_ATTRIBUTE);
		if (DEFAULT_VALUE.equals(merge)) {
			merge = parentDefaults != null ? parentDefaults.getMerge() : FALSE_VALUE;
		}
		defaults.setMerge(merge);
		//获取default-autowire属性
		String autowire = root.getAttribute(DEFAULT_AUTOWIRE_ATTRIBUTE);
		if (DEFAULT_VALUE.equals(autowire)) {
			autowire = parentDefaults != null ? parentDefaults.getAutowire() : AUTOWIRE_NO_VALUE;
		}
		defaults.setAutowire(autowire);

		//设置defult-dependecny-check
		defaults.setDependencyCheck(root.getAttribute(DEFAULT_DEPENDENCY_CHECK_ATTRIBUTE));
		
		if (root.hasAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE)) {
			defaults.setAutowireCandidates(root.getAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE));
		}
		else if (parentDefaults != null) {
			defaults.setAutowireCandidates(parentDefaults.getAutowireCandidates());
		}

		if (root.hasAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE)) {
			defaults.setInitMethod(root.getAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE));
		}
		else if (parentDefaults != null) {
			defaults.setInitMethod(parentDefaults.getInitMethod());
		}

		if (root.hasAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE)) {
			defaults.setDestroyMethod(root.getAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE));
		}
		else if (parentDefaults != null) {
			defaults.setDestroyMethod(parentDefaults.getDestroyMethod());
		}

		defaults.setSource(this.readerContext.extractSource(root));
	}

	/**
	 * 获取默认值
	 */
	public DocumentDefaultsDefinition getDefaults() {
		return this.defaults;
	}

	
	public BeanDefinitionDefaults getBeanDefinitionDefaults() {
		BeanDefinitionDefaults bdd = new BeanDefinitionDefaults();
		bdd.setLazyInit("TRUE".equalsIgnoreCase(this.defaults.getLazyInit()));
		bdd.setDependencyCheck(this.getDependencyCheck(DEFAULT_VALUE));
		bdd.setAutowireMode(this.getAutowireMode(DEFAULT_VALUE));
		bdd.setInitMethodName(this.defaults.getInitMethod());
		bdd.setDestroyMethodName(this.defaults.getDestroyMethod());
		return bdd;
	}

	
	public String[] getAutowireCandidatePatterns() {
		String candidatePattern = this.defaults.getAutowireCandidates();
		return (candidatePattern != null ? StringUtils.commaDelimitedListToStringArray(candidatePattern) : null);
	}


	/**
	 * 解析<bean>节点,如果在解析过程中发生异常可能返回null
	 */
	public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
		return parseBeanDefinitionElement(ele, null);
	}

	/**
	 */
	public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
		//获取<bean>节点的id属性,如<bean id="man" ... />,则id=man
		String id = ele.getAttribute(ID_ATTRIBUTE);
		//获取name属性值
		String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
		
		List<String> aliases = new ArrayList<String>();
		//如果name属性值不为空,拆分多个name,并保存到list中
		if (StringUtils.hasLength(nameAttr)) {
			String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
			aliases.addAll(Arrays.asList(nameArr));
		}
		//将id赋值给beanName
		String beanName = id;
		//如果beanName不为空且别名的列表不为空则将别名集合中的第一个值赋值为beanName
		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");
			}
		}
		//beanName的唯一性检查,beanName和别名都不能和已有的bean id或别名重复
		if (containingBean == null) {
			checkNameUniqueness(beanName, aliases, ele);
		}
		// 如果当前bean 的id和别名都没有重复值则解析bean节点
		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);
			return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
		}

		return null;
	}

	/**
	 * 校验制定的bean的名称和别名在当前级别的beans嵌套内没有使用过
	 */
	protected void checkNameUniqueness(String beanName, List<String> aliases, Element beanElement) {
		//定义一个找到的beanName,初始化值为null
		String foundName = null;
		//beanName不为空且userNames中包含这个beanName则将beanName赋值为foundName
		if (StringUtils.hasText(beanName) && this.usedNames.contains(beanName)) {
			foundName = beanName;
		}
		//如果foundName不为null,则判断usedNames中是否包含别名,将包含的第一个别名赋值给foundName
		if (foundName == null) {
			foundName = (String) CollectionUtils.findFirstMatch(this.usedNames, aliases);
		}
		//如果foundName不为null则进行错误处理
		if (foundName != null) {
			error("Bean name '" + foundName + "' is already used in this <beans> element", beanElement);
		}
	    //向usedNames中添加beanName
		this.usedNames.add(beanName);
		//将aliases添加到usedNames
		this.usedNames.addAll(aliases);
	}

	/**
	 * 解析Bean
	 */
	public AbstractBeanDefinition parseBeanDefinitionElement(
			Element ele, String beanName, BeanDefinition containingBean) {
		//使用beanName创建一个BeanEntriy对象并放入parseState中
		this.parseState.push(new BeanEntry(beanName));
		
		String className = null;
		//如果bean节点中含有class属性,则将该获取该属性值
		if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
			className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
		}

		try {
		 // 如果bean节点含有parent属性则获取该属性
			String parent = null;
			if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
				parent = ele.getAttribute(PARENT_ATTRIBUTE);
			}
			//使用className和parent创建一个beanDefinition
			AbstractBeanDefinition bd = createBeanDefinition(className, parent);

			parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
			//设置description
			bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));

			parseMetaElements(ele, bd);
			//解析lookup-method元素
			parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
			//解析 replace-method元素
			parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
			//解析构造参数元素
			parseConstructorArgElements(ele, bd);
			//解析属性
			parsePropertyElements(ele, bd);
			
			parseQualifierElements(ele, bd);

			bd.setResource(this.readerContext.getResource());
			
			bd.setSource(extractSource(ele));

			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;
	}

	/**
	 * 解析给定的节点的属性值
	 * 
	 */
	public AbstractBeanDefinition parseBeanDefinitionAttributes(Element ele, String beanName,
			BeanDefinition containingBean, AbstractBeanDefinition bd) {
		//如果bean节点含有scope属性则设置BeanDefinition的scope属性
		if (ele.hasAttribute(SCOPE_ATTRIBUTE)) {
			bd.setScope(ele.getAttribute(SCOPE_ATTRIBUTE));
				//如果设置了scope属性同时设置了singleton,则进行错误处理!不允许同时设置scope和singleton
			if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
				error("Specify either 'scope' or 'singleton', not both", ele);
			}
		}
		else if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
			//如果bean节点中包含singletone属性且值为true,则设置scope属性为singleton否则设置为prototype
			bd.setScope(TRUE_VALUE.equals(ele.getAttribute(SINGLETON_ATTRIBUTE)) ?
					BeanDefinition.SCOPE_SINGLETON : BeanDefinition.SCOPE_PROTOTYPE);
		}
		else if (containingBean != null) {
			// 如果含有内部bean则作用域以内部bean为准.
			bd.setScope(containingBean.getScope());
		}
		//如果bean节点包含abstract值且值为true则设置beanDefinition的值为true否则设置为false
		if (ele.hasAttribute(ABSTRACT_ATTRIBUTE)) {
			bd.setAbstract(TRUE_VALUE.equals(ele.getAttribute(ABSTRACT_ATTRIBUTE)));
		}
		//获取lazy-init属性
		String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE);
		//如果lazyInit的值等于default则使用beans根节点中设置的default-lazy-init值
		if (DEFAULT_VALUE.equals(lazyInit)) {
			lazyInit = this.defaults.getLazyInit();
		}
		bd.setLazyInit(TRUE_VALUE.equals(lazyInit));
		//获取bean节点autowire属性值
		String autowire = ele.getAttribute(AUTOWIRE_ATTRIBUTE);
		//设置beanDefinition的AutowireMode
		bd.setAutowireMode(getAutowireMode(autowire));
		//获取dependency-check属性
		String dependencyCheck = ele.getAttribute(DEPENDENCY_CHECK_ATTRIBUTE);
		bd.setDependencyCheck(getDependencyCheck(dependencyCheck));
		//如果bean节点中包含depends-on属性值
		if (ele.hasAttribute(DEPENDS_ON_ATTRIBUTE)) {
		  //获取depends-on节点值
			String dependsOn = ele.getAttribute(DEPENDS_ON_ATTRIBUTE);
			//设置beandefinition的dependsOn属性
			bd.setDependsOn(StringUtils.tokenizeToStringArray(dependsOn, MULTI_VALUE_ATTRIBUTE_DELIMITERS));
		}
		//获取autowire-candidate属性值
		String autowireCandidate = ele.getAttribute(AUTOWIRE_CANDIDATE_ATTRIBUTE);
		//如果autowireCandidate的值是空获取是default
		if ("".equals(autowireCandidate) || DEFAULT_VALUE.equals(autowireCandidate)) {
			//获取beans节点中设置的default-autowire-candidates属性值
			String candidatePattern = this.defaults.getAutowireCandidates();
			//如果candidatePattern不为null
			if (candidatePattern != null) {
				//将candidatePattern使用,分割为字符串数组
				String[] patterns = StringUtils.commaDelimitedListToStringArray(candidatePattern);
				//如果正则匹配beanName则设置为true否则设置为false
				bd.setAutowireCandidate(PatternMatchUtils.simpleMatch(patterns, beanName));
			}
		}
		else {
			//如果没有设置autowire-candidate或者值不是false,如果其值是true则设置为true否则设置为false
			bd.setAutowireCandidate(TRUE_VALUE.equals(autowireCandidate));
		}
		// 如果bean节点包含primary属性,则设置beanDefinition的primary属性
		if (ele.hasAttribute(PRIMARY_ATTRIBUTE)) {
			bd.setPrimary(TRUE_VALUE.equals(ele.getAttribute(PRIMARY_ATTRIBUTE)));
		}
		//如果bean节点中包含init-method属性
		if (ele.hasAttribute(INIT_METHOD_ATTRIBUTE)) {
			//获取init-method属性值
			String initMethodName = ele.getAttribute(INIT_METHOD_ATTRIBUTE);
			//如果initMethodName不是空字符串则设置initMethodName
			if (!"".equals(initMethodName)) {
				bd.setInitMethodName(initMethodName);
			}
		}
		else {
			//如果bean节点没有设置init-method,但是beans节点中设置了default-init-method
			if (this.defaults.getInitMethod() != null) {
				bd.setInitMethodName(this.defaults.getInitMethod());
				bd.setEnforceInitMethod(false);
			}
		}
		//如果bean节点中包含destory-method或者beans节点中设置了defult-destory-method属性则设置beanDefinition的destroyMethod
		if (ele.hasAttribute(DESTROY_METHOD_ATTRIBUTE)) {
			String destroyMethodName = ele.getAttribute(DESTROY_METHOD_ATTRIBUTE);
			if (!"".equals(destroyMethodName)) {
				bd.setDestroyMethodName(destroyMethodName);
			}
		}
		else {
			if (this.defaults.getDestroyMethod() != null) {
				bd.setDestroyMethodName(this.defaults.getDestroyMethod());
				bd.setEnforceDestroyMethod(false);
			}
		}
		//如果bean节点中包含了factory-method,则设置beanDefinition的factoryMethod
		if (ele.hasAttribute(FACTORY_METHOD_ATTRIBUTE)) {
			bd.setFactoryMethodName(ele.getAttribute(FACTORY_METHOD_ATTRIBUTE));
		}
		//如果bean节点设置了factory-bean则设置beanDefinition的factoryBean
		if (ele.hasAttribute(FACTORY_BEAN_ATTRIBUTE)) {
			bd.setFactoryBeanName(ele.getAttribute(FACTORY_BEAN_ATTRIBUTE));
		}

		return bd;
	}

	/**
	 * 使用给定的类名称和父类名称创建一个BeanDifinition
	 */
	protected AbstractBeanDefinition createBeanDefinition(String className, String parentName)
			throws ClassNotFoundException {

		return BeanDefinitionReaderUtils.createBeanDefinition(
				parentName, className, this.readerContext.getBeanClassLoader());
	}
	//解析Bean的元节点
	public void parseMetaElements(Element ele, BeanMetadataAttributeAccessor attributeAccessor) {
		//获取bean所有子节点
		NodeList nl = ele.getChildNodes();
		//遍历所有元节点
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			/
			if (isCandidateElement(node) && nodeNameEquals(node, META_ELEMENT)) {
			// 强制类型转换
				Element metaElement = (Element) node;
				//获取key
				String key = metaElement.getAttribute(KEY_ATTRIBUTE);
				//获取value
				String value = metaElement.getAttribute(VALUE_ATTRIBUTE);
				//使用key,value构成一个元属性
				BeanMetadataAttribute attribute = new BeanMetadataAttribute(key, value);
				attribute.setSource(extractSource(metaElement));
				attributeAccessor.addMetadataAttribute(attribute);
			}
		}
	}

	public int getAutowireMode(String attValue) {
		String att = attValue;
		if (DEFAULT_VALUE.equals(att)) {
			att = this.defaults.getAutowire();
		}
		int autowire = AbstractBeanDefinition.AUTOWIRE_NO;
		if (AUTOWIRE_BY_NAME_VALUE.equals(att)) {
			autowire = AbstractBeanDefinition.AUTOWIRE_BY_NAME;
		}
		else if (AUTOWIRE_BY_TYPE_VALUE.equals(att)) {
			autowire = AbstractBeanDefinition.AUTOWIRE_BY_TYPE;
		}
		else if (AUTOWIRE_CONSTRUCTOR_VALUE.equals(att)) {
			autowire = AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR;
		}
		else if (AUTOWIRE_AUTODETECT_VALUE.equals(att)) {
			autowire = AbstractBeanDefinition.AUTOWIRE_AUTODETECT;
		}
		// Else leave default value.
		return autowire;
	}

	public int getDependencyCheck(String attValue) {
		String att = attValue;
		if (DEFAULT_VALUE.equals(att)) {
			att = this.defaults.getDependencyCheck();
		}
		if (DEPENDENCY_CHECK_ALL_ATTRIBUTE_VALUE.equals(att)) {
			return AbstractBeanDefinition.DEPENDENCY_CHECK_ALL;
		}
		else if (DEPENDENCY_CHECK_OBJECTS_ATTRIBUTE_VALUE.equals(att)) {
			return AbstractBeanDefinition.DEPENDENCY_CHECK_OBJECTS;
		}
		else if (DEPENDENCY_CHECK_SIMPLE_ATTRIBUTE_VALUE.equals(att)) {
			return AbstractBeanDefinition.DEPENDENCY_CHECK_SIMPLE;
		}
		else {
			return AbstractBeanDefinition.DEPENDENCY_CHECK_NONE;
		}
	}

	/**
	 * 解析构造参数元素
	 */
	public void parseConstructorArgElements(Element beanEle, BeanDefinition bd) {
		NodeList nl = beanEle.getChildNodes();
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			if (isCandidateElement(node) && nodeNameEquals(node, CONSTRUCTOR_ARG_ELEMENT)) {
				parseConstructorArgElement((Element) node, bd);
			}
		}
	}

	/**
	 * 解析给定bean节点的属性元素
	 */
	public void parsePropertyElements(Element beanEle, BeanDefinition bd) {
		NodeList nl = beanEle.getChildNodes();
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			if (isCandidateElement(node) && nodeNameEquals(node, PROPERTY_ELEMENT)) {
				parsePropertyElement((Element) node, bd);
			}
		}
	}

	/**
	 * 解析给定元素的 qualifier 子节点
	 */
	public void parseQualifierElements(Element beanEle, AbstractBeanDefinition bd) {
		NodeList nl = beanEle.getChildNodes();
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			if (isCandidateElement(node) && nodeNameEquals(node, QUALIFIER_ELEMENT)) {
				parseQualifierElement((Element) node, bd);
			}
		}
	}

	/**
	 *解析给定节点的lookup-method子节点
	 */
	public void parseLookupOverrideSubElements(Element beanEle, MethodOverrides overrides) {
		//获取bean节点的所有子节点
		NodeList nl = beanEle.getChildNodes();
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			//如果节点是lookup-method
			if (isCandidateElement(node) && nodeNameEquals(node, LOOKUP_METHOD_ELEMENT)) {
				Element ele = (Element) node;
				String methodName = ele.getAttribute(NAME_ATTRIBUTE);
				String beanRef = ele.getAttribute(BEAN_ELEMENT);
				LookupOverride override = new LookupOverride(methodName, beanRef);
				override.setSource(extractSource(ele));
				overrides.addOverride(override);
			}
		}
	}

	/**
	 *
	 */
	public void parseReplacedMethodSubElements(Element beanEle, MethodOverrides overrides) {
		NodeList nl = beanEle.getChildNodes();
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			if (isCandidateElement(node) && nodeNameEquals(node, REPLACED_METHOD_ELEMENT)) {
				Element replacedMethodEle = (Element) node;
				String name = replacedMethodEle.getAttribute(NAME_ATTRIBUTE);
				String callback = replacedMethodEle.getAttribute(REPLACER_ATTRIBUTE);
				ReplaceOverride replaceOverride = new ReplaceOverride(name, callback);
				// Look for arg-type match elements.
				List<Element> argTypeEles = DomUtils.getChildElementsByTagName(replacedMethodEle, ARG_TYPE_ELEMENT);
				for (Element argTypeEle : argTypeEles) {
					String match = argTypeEle.getAttribute(ARG_TYPE_MATCH_ATTRIBUTE);
					match = (StringUtils.hasText(match) ? match : DomUtils.getTextValue(argTypeEle));
					if (StringUtils.hasText(match)) {
						replaceOverride.addTypeIdentifier(match);
					}					
				}
				replaceOverride.setSource(extractSource(replacedMethodEle));
				overrides.addOverride(replaceOverride);
			}
		}
	}

	/**
	 * 
	 */
	public void parseConstructorArgElement(Element ele, BeanDefinition bd) {
		String indexAttr = ele.getAttribute(INDEX_ATTRIBUTE);
		String typeAttr = ele.getAttribute(TYPE_ATTRIBUTE);
		String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
		if (StringUtils.hasLength(indexAttr)) {
			try {
				int index = Integer.parseInt(indexAttr);
				if (index < 0) {
					error("'index' cannot be lower than 0", ele);
				}
				else {
					try {
						this.parseState.push(new ConstructorArgumentEntry(index));
						Object value = parsePropertyValue(ele, bd, null);
						ConstructorArgumentValues.ValueHolder valueHolder = new ConstructorArgumentValues.ValueHolder(value);
						if (StringUtils.hasLength(typeAttr)) {
							valueHolder.setType(typeAttr);
						}
						if (StringUtils.hasLength(nameAttr)) {
							valueHolder.setName(nameAttr);
						}
						valueHolder.setSource(extractSource(ele));
						if (bd.getConstructorArgumentValues().hasIndexedArgumentValue(index)) {
							error("Ambiguous constructor-arg entries for index " + index, ele);
						}
						else {
							bd.getConstructorArgumentValues().addIndexedArgumentValue(index, valueHolder);
						}
					}
					finally {
						this.parseState.pop();
					}
				}
			}
			catch (NumberFormatException ex) {
				error("Attribute 'index' of tag 'constructor-arg' must be an integer", ele);
			}
		}
		else {
			try {
				this.parseState.push(new ConstructorArgumentEntry());
				Object value = parsePropertyValue(ele, bd, null);
				ConstructorArgumentValues.ValueHolder valueHolder = new ConstructorArgumentValues.ValueHolder(value);
				if (StringUtils.hasLength(typeAttr)) {
					valueHolder.setType(typeAttr);
				}
				if (StringUtils.hasLength(nameAttr)) {
					valueHolder.setName(nameAttr);
				}
				valueHolder.setSource(extractSource(ele));
				bd.getConstructorArgumentValues().addGenericArgumentValue(valueHolder);
			}
			finally {
				this.parseState.pop();
			}
		}
	}

	/**
	 * 
	 */
	public void parsePropertyElement(Element ele, BeanDefinition bd) {
		String propertyName = ele.getAttribute(NAME_ATTRIBUTE);
		if (!StringUtils.hasLength(propertyName)) {
			error("Tag 'property' must have a 'name' attribute", ele);
			return;
		}
		this.parseState.push(new PropertyEntry(propertyName));
		try {
			if (bd.getPropertyValues().contains(propertyName)) {
				error("Multiple 'property' definitions for property '" + propertyName + "'", ele);
				return;
			}
			Object val = parsePropertyValue(ele, bd, propertyName);
			PropertyValue pv = new PropertyValue(propertyName, val);
			parseMetaElements(ele, pv);
			pv.setSource(extractSource(ele));
			bd.getPropertyValues().addPropertyValue(pv);
		}
		finally {
			this.parseState.pop();
		}
	}

	/**
	 * 
	 */
	public void parseQualifierElement(Element ele, AbstractBeanDefinition bd) {
		String typeName = ele.getAttribute(TYPE_ATTRIBUTE);
		if (!StringUtils.hasLength(typeName)) {
			error("Tag 'qualifier' must have a 'type' attribute", ele);
			return;
		}
		this.parseState.push(new QualifierEntry(typeName));
		try {
			AutowireCandidateQualifier qualifier = new AutowireCandidateQualifier(typeName);
			qualifier.setSource(extractSource(ele));
			String value = ele.getAttribute(VALUE_ATTRIBUTE);
			if (StringUtils.hasLength(value)) {
				qualifier.setAttribute(AutowireCandidateQualifier.VALUE_KEY, value);
			}
			NodeList nl = ele.getChildNodes();
			for (int i = 0; i < nl.getLength(); i++) {
				Node node = nl.item(i);
				if (isCandidateElement(node) && nodeNameEquals(node, QUALIFIER_ATTRIBUTE_ELEMENT)) {
					Element attributeEle = (Element) node;
					String attributeName = attributeEle.getAttribute(KEY_ATTRIBUTE);
					String attributeValue = attributeEle.getAttribute(VALUE_ATTRIBUTE);
					if (StringUtils.hasLength(attributeName) && StringUtils.hasLength(attributeValue)) {
						BeanMetadataAttribute attribute = new BeanMetadataAttribute(attributeName, attributeValue);
						attribute.setSource(extractSource(attributeEle));
						qualifier.addMetadataAttribute(attribute);
					}
					else {
						error("Qualifier 'attribute' tag must have a 'name' and 'value'", attributeEle);
						return;
					}
				}
			}
			bd.addQualifier(qualifier);
		}
		finally {
			this.parseState.pop();
		}
	}

	/**
	 * 获取指定属性的值
	 */
	public Object parsePropertyValue(Element ele, BeanDefinition bd, String propertyName) {
		String elementName = (propertyName != null) ?
						"<property> element for property '" + propertyName + "'" :
						"<constructor-arg> element";

		// Should only have one child element: ref, value, list, etc.
		NodeList nl = ele.getChildNodes();
		Element subElement = null;
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT) &&
					!nodeNameEquals(node, META_ELEMENT)) {
				// Child element is what we're looking for.
				if (subElement != null) {
					error(elementName + " must not contain more than one sub-element", ele);
				}
				else {
					subElement = (Element) node;
				}
			}
		}

		boolean hasRefAttribute = ele.hasAttribute(REF_ATTRIBUTE);
		boolean hasValueAttribute = ele.hasAttribute(VALUE_ATTRIBUTE);
		if ((hasRefAttribute && hasValueAttribute) ||
				((hasRefAttribute || hasValueAttribute) && subElement != null)) {
			error(elementName +
					" is only allowed to contain either 'ref' attribute OR 'value' attribute OR sub-element", ele);
		}

		if (hasRefAttribute) {
			String refName = ele.getAttribute(REF_ATTRIBUTE);
			if (!StringUtils.hasText(refName)) {
				error(elementName + " contains empty 'ref' attribute", ele);
			}
			RuntimeBeanReference ref = new RuntimeBeanReference(refName);
			ref.setSource(extractSource(ele));
			return ref;
		}
		else if (hasValueAttribute) {
			TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE));
			valueHolder.setSource(extractSource(ele));
			return valueHolder;
		}
		else if (subElement != null) {
			return parsePropertySubElement(subElement, bd);
		}
		else {
			// Neither child element nor "ref" or "value" attribute found.
			error(elementName + " must specify a ref or value", ele);
			return null;
		}
	}

	public Object parsePropertySubElement(Element ele, BeanDefinition bd) {
		return parsePropertySubElement(ele, bd, null);
	}

	/**
	 *解析一个属性的子节点
	 */
	public Object parsePropertySubElement(Element ele, BeanDefinition bd, String defaultValueType) {
		//如果子节点的命名空间是默认命名空间的
		if (!isDefaultNamespace(ele)) {
			return parseNestedCustomElement(ele, bd);
		}
		else if (nodeNameEquals(ele, BEAN_ELEMENT)) {
		//如果子节点是bean则解析该bean配置
			BeanDefinitionHolder nestedBd = parseBeanDefinitionElement(ele, bd);
			if (nestedBd != null) {
				nestedBd = decorateBeanDefinitionIfRequired(ele, nestedBd, bd);
			}
			//返回嵌套bean
			return nestedBd;
		}
		else if (nodeNameEquals(ele, REF_ELEMENT)) {
			//如果子节是ref,获取引用bean 名称
			String refName = ele.getAttribute(BEAN_REF_ATTRIBUTE);
			boolean toParent = false;
			//如果引用bean名称为空
			if (!StringUtils.hasLength(refName)) {
				//获取local值
				refName = ele.getAttribute(LOCAL_REF_ATTRIBUTE);
				//如果local值为空
				if (!StringUtils.hasLength(refName)) {
					// 获取parent值
					refName = ele.getAttribute(PARENT_REF_ATTRIBUTE);
					toParent = true;
					//如果parent值也为空则进行错误处理
					if (!StringUtils.hasLength(refName)) {
						error("'bean', 'local' or 'parent' is required for <ref> element", ele);
						return null;
					}
				}
			}
			// 如果refName中不包含文字则进行错误处理
			if (!StringUtils.hasText(refName)) {
				error("<ref> element contains empty target attribute", ele);
				return null;
			}
			//创建一个RuntimeBeanReference对象
			RuntimeBeanReference ref = new RuntimeBeanReference(refName, toParent);
			ref.setSource(extractSource(ele));
			return ref;
		}
		else if (nodeNameEquals(ele, IDREF_ELEMENT)) {
			//如果节点是idref
			return parseIdRefElement(ele);
		}
		else if (nodeNameEquals(ele, VALUE_ELEMENT)) {
		   // 如果节点是value
			return parseValueElement(ele, defaultValueType);
		}
		else if (nodeNameEquals(ele, NULL_ELEMENT)) {
			//如果节点是null
			TypedStringValue nullHolder = new TypedStringValue(null);
			nullHolder.setSource(extractSource(ele));
			return nullHolder;
		}
		else if (nodeNameEquals(ele, ARRAY_ELEMENT)) {
		  //如果节点是array
			return parseArrayElement(ele, bd);
		}
		else if (nodeNameEquals(ele, LIST_ELEMENT)) {
			//如果节点是list
			return parseListElement(ele, bd);
		}
		else if (nodeNameEquals(ele, SET_ELEMENT)) {
			//如果节点是set
			return parseSetElement(ele, bd);
		}
		else if (nodeNameEquals(ele, MAP_ELEMENT)) {
			//如果节点是map
			return parseMapElement(ele, bd);
		}
		else if (nodeNameEquals(ele, PROPS_ELEMENT)) {
		//如果节点是props
			return parsePropsElement(ele);
		}
		else {
			error("Unknown property sub-element: [" + ele.getNodeName() + "]", ele);
			return null;
		}
	}

	/**
	 * 
	 */
	public Object parseIdRefElement(Element ele) {
		// A generic reference to any name of any bean.
		String refName = ele.getAttribute(BEAN_REF_ATTRIBUTE);
		if (!StringUtils.hasLength(refName)) {
			// A reference to the id of another bean in the same XML file.
			refName = ele.getAttribute(LOCAL_REF_ATTRIBUTE);
			if (!StringUtils.hasLength(refName)) {
				error("Either 'bean' or 'local' is required for <idref> element", ele);
				return null;
			}
		}
		if (!StringUtils.hasText(refName)) {
			error("<idref> element contains empty target attribute", ele);
			return null;
		}
		RuntimeBeanNameReference ref = new RuntimeBeanNameReference(refName);
		ref.setSource(extractSource(ele));
		return ref;
	}

	/**
	 * Return a typed String value Object for the given value element.
	 */
	public Object parseValueElement(Element ele, String defaultTypeName) {
		// It's a literal value.
		String value = DomUtils.getTextValue(ele);
		String specifiedTypeName = ele.getAttribute(TYPE_ATTRIBUTE);
		String typeName = specifiedTypeName;
		if (!StringUtils.hasText(typeName)) {
			typeName = defaultTypeName;
		}
		try {
			TypedStringValue typedValue = buildTypedStringValue(value, typeName);
			typedValue.setSource(extractSource(ele));
			typedValue.setSpecifiedTypeName(specifiedTypeName);
			return typedValue;
		}
		catch (ClassNotFoundException ex) {
			error("Type class [" + typeName + "] not found for <value> element", ele, ex);
			return value;
		}
	}

	/**
	 * 根据给定的值,已经类型创建一个TypedStringValue
	 */
	protected TypedStringValue buildTypedStringValue(String value, String targetTypeName)
			throws ClassNotFoundException {

		ClassLoader classLoader = this.readerContext.getBeanClassLoader();
		TypedStringValue typedValue;
		if (!StringUtils.hasText(targetTypeName)) {
			typedValue = new TypedStringValue(value);
		}
		else if (classLoader != null) {
			Class<?> targetType = ClassUtils.forName(targetTypeName, classLoader);
			typedValue = new TypedStringValue(value, targetType);
		}
		else {
			typedValue = new TypedStringValue(value, targetTypeName);
		}
		return typedValue;
	}

	/**
	 * 解析array节点
	 */
	public Object parseArrayElement(Element arrayEle, BeanDefinition bd) {
		//获取value-type
		String elementType = arrayEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
		//获取子节点
		NodeList nl = arrayEle.getChildNodes();
		//根据value-type和子节点长度创建一个ManagedArray
		ManagedArray target = new ManagedArray(elementType, nl.getLength());
		target.setSource(extractSource(arrayEle));
		target.setElementTypeName(elementType);
		target.setMergeEnabled(parseMergeAttribute(arrayEle));
		parseCollectionElements(nl, target, bd, elementType);
		return target;
	}

	/**
	 * Parse a list element.
	 */
	public List parseListElement(Element collectionEle, BeanDefinition bd) {
		String defaultElementType = collectionEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
		NodeList nl = collectionEle.getChildNodes();
		ManagedList<Object> target = new ManagedList<Object>(nl.getLength());
		target.setSource(extractSource(collectionEle));
		target.setElementTypeName(defaultElementType);
		target.setMergeEnabled(parseMergeAttribute(collectionEle));
		parseCollectionElements(nl, target, bd, defaultElementType);
		return target;
	}

	/**
	 * Parse a set element.
	 */
	public Set parseSetElement(Element collectionEle, BeanDefinition bd) {
		String defaultElementType = collectionEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
		NodeList nl = collectionEle.getChildNodes();
		ManagedSet<Object> target = new ManagedSet<Object>(nl.getLength());
		target.setSource(extractSource(collectionEle));
		target.setElementTypeName(defaultElementType);
		target.setMergeEnabled(parseMergeAttribute(collectionEle));
		parseCollectionElements(nl, target, bd, defaultElementType);
		return target;
	}

	protected void parseCollectionElements(
			NodeList elementNodes, Collection<Object> target, BeanDefinition bd, String defaultElementType) {
		//遍历子节点
		for (int i = 0; i < elementNodes.getLength(); i++) {
			Node node = elementNodes.item(i);
			//如果节点是element且不是description则将其添加到target中
			if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT)) {
				target.add(parsePropertySubElement((Element) node, bd, defaultElementType));
			}
		}
	}

	/**
	 * 解析map节点
	 */
	public Map parseMapElement(Element mapEle, BeanDefinition bd) {
		//获取key-type
		String defaultKeyType = mapEle.getAttribute(KEY_TYPE_ATTRIBUTE);
		//获取value-type
		String defaultValueType = mapEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
		//获取map节点的所有entry子节点
		List<Element> entryEles = DomUtils.getChildElementsByTagName(mapEle, ENTRY_ELEMENT);
		//根据entry子节点的数量创建一个ManagedMap
		ManagedMap<Object, Object> map = new ManagedMap<Object, Object>(entryEles.size());
		map.setSource(extractSource(mapEle));
		//设置KeyType
		map.setKeyTypeName(defaultKeyType);
		//设置valueType
		map.setValueTypeName(defaultValueType);
		map.setMergeEnabled(parseMergeAttribute(mapEle));
         //遍历Entry
		for (Element entryEle : entryEles) {
			 //获取entry的子节点
			NodeList entrySubNodes = entryEle.getChildNodes();
			Element keyEle = null;
			Element valueEle = null;
				//遍历entry子节点
			for (int j = 0; j < entrySubNodes.getLength(); j++) {
				Node node = entrySubNodes.item(j);
				if (node instanceof Element) {
					Element candidateEle = (Element) node;
					if (nodeNameEquals(candidateEle, KEY_ELEMENT)) {
						if (keyEle != null) {
							error("<entry> element is only allowed to contain one <key> sub-element", entryEle);
						}
						else {
							keyEle = candidateEle;
						}
					}
					else {
						// Child element is what we're looking for.
						if (nodeNameEquals(candidateEle, DESCRIPTION_ELEMENT)) {
							// the element is a <description> -> ignore it
						}
						else if (valueEle != null) {
							error("<entry> element must not contain more than one value sub-element", entryEle);
						}
						else {
							valueEle = candidateEle;
						}
					}
				}
			}

			
			Object key = null;
			//entry节点是否包含key属性
			boolean hasKeyAttribute = entryEle.hasAttribute(KEY_ATTRIBUTE);
			//entry节点是否包含key-ref属性
			boolean hasKeyRefAttribute = entryEle.hasAttribute(KEY_REF_ATTRIBUTE);
			//key,key-ref,或者key的子节点不能同时配置,	
			if ((hasKeyAttribute && hasKeyRefAttribute) ||
					((hasKeyAttribute || hasKeyRefAttribute)) && keyEle != null) {
				error("<entry> element is only allowed to contain either " +
						"a 'key' attribute OR a 'key-ref' attribute OR a <key> sub-element", entryEle);
			}
			
			if (hasKeyAttribute) {
			//如果含有key属性则更具key属性值创建一个TypedStringValue
				key = buildTypedStringValueForMap(entryEle.getAttribute(KEY_ATTRIBUTE), defaultKeyType, entryEle);
			}
			else if (hasKeyRefAttribute) {
				//如果含有key-ref且值不为空则创建一个RuntimeBaseReference
				String refName = entryEle.getAttribute(KEY_REF_ATTRIBUTE);
				if (!StringUtils.hasText(refName)) {
					error("<entry> element contains empty 'key-ref' attribute", entryEle);
				}
				RuntimeBeanReference ref = new RuntimeBeanReference(refName);
				ref.setSource(extractSource(entryEle));
				key = ref;
			}
			else if (keyEle != null) {
				key = parseKeyElement(keyEle, bd, defaultKeyType);
			}
			else {
				error("<entry> element must specify a key", entryEle);
			}

			
			Object value = null;
			boolean hasValueAttribute = entryEle.hasAttribute(VALUE_ATTRIBUTE);
			boolean hasValueRefAttribute = entryEle.hasAttribute(VALUE_REF_ATTRIBUTE);
			if ((hasValueAttribute && hasValueRefAttribute) ||
					((hasValueAttribute || hasValueRefAttribute)) && valueEle != null) {
				error("<entry> element is only allowed to contain either " +
						"'value' attribute OR 'value-ref' attribute OR <value> sub-element", entryEle);
			}
			if (hasValueAttribute) {
				//如果有value属性则根据value属性的值创建一个TypeStringValue
				value = buildTypedStringValueForMap(entryEle.getAttribute(VALUE_ATTRIBUTE), defaultValueType, entryEle);
			}
			else if (hasValueRefAttribute) {
				String refName = entryEle.getAttribute(VALUE_REF_ATTRIBUTE);
				if (!StringUtils.hasText(refName)) {
					error("<entry> element contains empty 'value-ref' attribute", entryEle);
				}
				RuntimeBeanReference ref = new RuntimeBeanReference(refName);
				ref.setSource(extractSource(entryEle));
				value = ref;
			}
			else if (valueEle != null) {
				value = parsePropertySubElement(valueEle, bd, defaultValueType);
			}
			else {
				error("<entry> element must specify a value", entryEle);
			}

			//向Map中添加数据
			map.put(key, value);
		}

		return map;
	}

	/**
	 *创建一个TypedStringValue
	 */
	protected final Object buildTypedStringValueForMap(String value, String defaultTypeName, Element entryEle) {
		try {
			//创建一个TypeStringValue
			TypedStringValue typedValue = buildTypedStringValue(value, defaultTypeName);
			typedValue.setSource(extractSource(entryEle));
			return typedValue;
		}
		catch (ClassNotFoundException ex) {
			error("Type class [" + defaultTypeName + "] not found for Map key/value type", entryEle, ex);
			return value;
		}
	}

	/**
	 * 解析key的子节点
	 */
	protected Object parseKeyElement(Element keyEle, BeanDefinition bd, String defaultKeyTypeName) {
	   //获取key的所有子节点
		NodeList nl = keyEle.getChildNodes();
		Element subElement = null;
		for (int i = 0; i < nl.getLength(); i++) {
			Node node = nl.item(i);
			if (node instanceof Element) {
				// Child element is what we're looking for.
				if (subElement != null) {
					error("<key> element must not contain more than one value sub-element", keyEle);
				}
				else {
					subElement = (Element) node;
				}
			}
		}
		return parsePropertySubElement(subElement, bd, defaultKeyTypeName);
	}

	/**
	 * Parse a props element.
	 */
	public Properties parsePropsElement(Element propsEle) {
		ManagedProperties props = new ManagedProperties();
		props.setSource(extractSource(propsEle));
		props.setMergeEnabled(parseMergeAttribute(propsEle));

		List<Element> propEles = DomUtils.getChildElementsByTagName(propsEle, PROP_ELEMENT);
		for (Element propEle : propEles) {
			String key = propEle.getAttribute(KEY_ATTRIBUTE);
			// Trim the text value to avoid unwanted whitespace
			// caused by typical XML formatting.
			String value = DomUtils.getTextValue(propEle).trim();
			TypedStringValue keyHolder = new TypedStringValue(key);
			keyHolder.setSource(extractSource(propEle));
			TypedStringValue valueHolder = new TypedStringValue(value);
			valueHolder.setSource(extractSource(propEle));
			props.put(keyHolder, valueHolder);
		}

		return props;
	}

	/**
	 * Parse the merge attribute of a collection element, if any.
	 */
	public boolean parseMergeAttribute(Element collectionElement) {
		String value = collectionElement.getAttribute(MERGE_ATTRIBUTE);
		if (DEFAULT_VALUE.equals(value)) {
			value = this.defaults.getMerge();
		}
		return TRUE_VALUE.equals(value);
	}

	public BeanDefinition parseCustomElement(Element ele) {
		return parseCustomElement(ele, null);
	}

	public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
		String namespaceUri = getNamespaceURI(ele);
		NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
		if (handler == null) {
			error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
			return null;
		}
		return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
	}
	
  /**
   * 装饰BeanDefinition
   **/
	public BeanDefinitionHolder decorateBeanDefinitionIfRequired(Element ele, BeanDefinitionHolder definitionHolder) {
		return decorateBeanDefinitionIfRequired(ele, definitionHolder, null);
	}

	public BeanDefinitionHolder decorateBeanDefinitionIfRequired(
			Element ele, BeanDefinitionHolder definitionHolder, BeanDefinition containingBd) {
		
		BeanDefinitionHolder finalDefinition = definitionHolder;

		// 获取节点的所有属性,[autowire,autowire-candidate,class,id,lazy-init]
		NamedNodeMap attributes = ele.getAttributes();
		//遍历属性
		for (int i = 0; i < attributes.getLength(); i++) {
			// autowire
			Node node = attributes.item(i);
			finalDefinition = decorateIfRequired(node, finalDefinition, containingBd);
		}

		NodeList children = ele.getChildNodes();
		for (int i = 0; i < children.getLength(); i++) {
			Node node = children.item(i);
			if (node.getNodeType() == Node.ELEMENT_NODE) {
				finalDefinition = decorateIfRequired(node, finalDefinition, containingBd);
			}
		}
		return finalDefinition;
	}

	private BeanDefinitionHolder decorateIfRequired(
			Node node, BeanDefinitionHolder originalDef, BeanDefinition containingBd) {
		//获取节点的命名空间,null
		String namespaceUri = getNamespaceURI(node);
		 //如果命名空间不是默认的命名空间
		if (!isDefaultNamespace(namespaceUri)) {
		    //获取命名空间处理器
			NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
			if (handler != null) {
				return handler.decorate(node, originalDef, new ParserContext(this.readerContext, this, containingBd));
			}
			else if (namespaceUri != null && namespaceUri.startsWith("http://www.springframework.org/")) {
				error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", node);
			}
			else {
				// A custom namespace, not to be handled by Spring - maybe "xml:...".
				if (logger.isDebugEnabled()) {
					logger.debug("No Spring NamespaceHandler found for XML schema namespace [" + namespaceUri + "]");
				}
			}
		}
		return originalDef;
	}

	private BeanDefinitionHolder parseNestedCustomElement(Element ele, BeanDefinition containingBd) {
		BeanDefinition innerDefinition = parseCustomElement(ele, containingBd);
		if (innerDefinition == null) {
			error("Incorrect usage of element '" + ele.getNodeName() + "' in a nested manner. " +
					"This tag cannot be used nested inside <property>.", ele);
			return null;
		}
		String id = ele.getNodeName() + BeanDefinitionReaderUtils.GENERATED_BEAN_NAME_SEPARATOR +
				ObjectUtils.getIdentityHexString(innerDefinition);
		if (logger.isDebugEnabled()) {
			logger.debug("Using generated bean name [" + id +
					"] for nested custom element '" + ele.getNodeName() + "'");
		}
		return new BeanDefinitionHolder(innerDefinition, id);
	}


	/**
	 *获取指定节点的NamespaceURI
	 */
	public String getNamespaceURI(Node node) {
		return node.getNamespaceURI();
	}

	
	public String getLocalName(Node node) {
		return node.getLocalName();
	}

	
	public boolean nodeNameEquals(Node node, String desiredName) {
		return desiredName.equals(node.getNodeName()) || desiredName.equals(getLocalName(node));
	}
	/**
	 * 如果给定的namespaceUri不为空且等于http://www.springframework.org/schema/beans 则是默认的命名空间
	 **/
	public boolean isDefaultNamespace(String namespaceUri) {
		return (!StringUtils.hasLength(namespaceUri) || BEANS_NAMESPACE_URI.equals(namespaceUri));
	}
   
    /**
	 * 判断给定的节点的namespaceUri是不是默认的命名空间值
	 **/
	public boolean isDefaultNamespace(Node node) {
		return isDefaultNamespace(getNamespaceURI(node));
	}

	private boolean isCandidateElement(Node node) {
		return (node instanceof Element && (isDefaultNamespace(node) || !isDefaultNamespace(node.getParentNode())));
	}

}

 

BeanDefinitionParserDelegate 源码分析

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