一 bean标签的解析和注册
1 解析BeanDefinition
<1> 创建用于属性承载的BeanDefinition
<2> 解析各种属性
<3> 解析子元素meta
<4> 子元素lookup-method的解析
<5> 解析子元素replaced-method
<6> 解析子元素constructor-arg
<7> 解析子元素property
<8> 解析子元素qualifier
2 AbstractBeanDefinition属性
<1> 解析默认标签中的自定义标签元素
3 注册解析的BeanDefinition
<3> 通知监听器解析及注册完成
3 alias标签的解析
4 import标签的解析
5 嵌入式beans的标签解析
默认标签的解析是在DefaultBeanDefinitionDocumentReader类的parseDefaultElement()方法中进行的，函数的功能逻辑分别对4种不同标签（import、alias、bean和beans）做了不同的处理。
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) { //对import标签处理 if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) { importBeanDefinitionResource(ele); } //对alias标签进行处理 else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) { processAliasRegistration(ele); } //对bean标签处理 else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { processBeanDefinition(ele, delegate); } //对beans标签处理 else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // recurse doRegisterBeanDefinitions(ele); } }在这4种标签中，bean的标签解析尤为重要。下面是对bean标签解析处理的方法processBeanDefinition(ele, delegate)。
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); if (bdHolder != null) { //若存在默认标签的子节点下再有自定义属性，还需要再次对自定义标签进行解析 bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // Register the final decorated instance. BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry()); } catch (BeanDefinitionStoreException ex) { getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, ex); } // Send registration event. getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder)); } }这个方法的大致逻辑如下：
首先委托BeanDefinitionParserDelegate类的parseBeanDefinitionElement()方法进行元素解析，返回BeanDefinitionHolder类型的实例bdHolder，bdHolder实例已经包含了配置文件中配置的各种属性，包括class、name、id、alias等之类的属性；当返回的bdHolder不空的情况下，若存在默认标签的子节点下再有自定义属性，还需要再次对自定义标签进行解析；解析完成后，需要对解析的bdHolder进行注册，注册操作委托给BeanDefinitionReaderUtils.registerBeanDefinition()方法；最后发出响应事件，通知相关的监听器，这个bean已经加载完成了。
BeanDefinitionParserDelegate类的parseBeanDefinitionElement()方法进行元素解析。
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) { return parseBeanDefinitionElement(ele, null); } public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) { //提取元素中的id以及name属性； String id = ele.getAttribute(ID_ATTRIBUTE); String nameAttr = ele.getAttribute(NAME_ATTRIBUTE); List<String> aliases = new ArrayList<>(); 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); } //进一步解析其他所有属性并统一封装至GenericBeanDefinition(它继承自AbstractBeanDefinition)的实例中； AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean); if (beanDefinition != null) { //如果检测到bean没有指定beanName，那么使用默认规则为此bean生成beanName； 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); //将获取到的信息封装到BeanDefinitionHolder的实例中 return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray); } return null; }有上面代码可以看出，在开始对属性进行全面解析前，Spring在外层又做了一个当前层的功能架构，在当前层完成的主要工作包括如下内容：
提取元素中的id以及name属性；进一步解析其他所有属性并统一封装至GenericBeanDefinition(它继承自AbstractBeanDefinition)的实例中；如果检测到bean没有指定beanName，那么使用默认规则为此bean生成beanName；将获取到的信息封装到BeanDefinitionHolder的实例中。下面来看一下第2步中，进一步解析其他属性的parseBeanDefinitionElement()方法都做了什么：
@Nullable public AbstractBeanDefinition parseBeanDefinitionElement( Element ele, String beanName, @Nullable BeanDefinition containingBean) { this.parseState.push(new BeanEntry(beanName)); String className = null; //解析class属性 if (ele.hasAttribute(CLASS_ATTRIBUTE)) { className = ele.getAttribute(CLASS_ATTRIBUTE).trim(); } String parent = null; //解析parent属性 if (ele.hasAttribute(PARENT_ATTRIBUTE)) { parent = ele.getAttribute(PARENT_ATTRIBUTE); } try { //创建用于承载属性的AbstractBeanDefinition类型的GenericBeanDefinition实例， AbstractBeanDefinition bd = createBeanDefinition(className, parent); //硬编码解析默认bean的各种属性 parseBeanDefinitionAttributes(ele, beanName, containingBean, bd); bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT)); //解析元数据 parseMetaElements(ele, bd); //解析lookup-method属性 parseLookupOverrideSubElements(ele, bd.getMethodOverrides()); //解析replaced-method属性 parseReplacedMethodSubElements(ele, bd.getMethodOverrides()); //解析构造函数参数 parseConstructorArgElements(ele, bd); //解析property子元素 parsePropertyElements(ele, bd); //解析qualifier子元素 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; }从下面方法可以看出它返回的是GenericBeanDefinition的实例，在createBeanDefinition()方法中它继续调用了BeanDefinitionReaderUtils类的createBeanDefinition()方法，下面是BeanDefinitionReaderUtils类的createBeanDefinition()方法代码。
public static AbstractBeanDefinition createBeanDefinition( @Nullable String parentName, @Nullable String className, @Nullable ClassLoader classLoader) throws ClassNotFoundException { GenericBeanDefinition bd = new GenericBeanDefinition(); bd.setParentName(parentName); if (className != null) { if (classLoader != null) { bd.setBeanClass(ClassUtils.forName(className, classLoader)); } else { bd.setBeanClassName(className); } } return bd; }BeanDefinition是一个接口，在Spring中有三个默认实现：RootBeanDefinition、ChildBeanDefinition和GenericBeanDefinition。这三种实现均继承自AbstractBeanDefinition，其中BeanDefinition是配置文件<bean>元素标签在容器中的内部表示方式。
<bean>元素标签拥有class、scope、lazy-init等配置属性，BeanDefinition在内部提供了相应的属性，它们是一一对应的。其中RootBeanDefinition是最常用的实现类，它对应一般性的<bean>元素标签，GenericBeanDefinition是自2.5版本后新加入的bean文件配置属性定义类，是一站式服务类。
在配置文件中可以定义父<bean>和子<bean>，父<bean>用RootBeanDefinition表示，而子<bean>用ChildBeanDefinition表示，而没有父<bean>的<bean>使用RootBeanDefinition表示。AbstractBeanDefinition是对两者共同的类信息进行抽象。
Spring通过BeanDefinition将配置文件中的<bean>配置信息转换为容器的内部表示，并将这些BeanDefinition注册到BeanDefinitionRegistry中。Spring容器的BeanDefinitionRegistry就像是Spring配置的数据库，主要是以map的方式保存，后续操作直接从BeanDefinitionRegistry中读取配置信息。
要解析属性就要先创建用于创建承载属性的实例，也就是创建GenericBeanDefinition。
下面是创建GenericBeanDefinition的createBeanDefinition方法代码：
protected AbstractBeanDefinition createBeanDefinition(@Nullable String className, @Nullable String parentName) throws ClassNotFoundException { return BeanDefinitionReaderUtils.createBeanDefinition( parentName, className, this.readerContext.getBeanClassLoader()); } public static AbstractBeanDefinition createBeanDefinition( @Nullable String parentName, @Nullable String className, @Nullable ClassLoader classLoader) throws ClassNotFoundException { GenericBeanDefinition bd = new GenericBeanDefinition(); bd.setParentName(parentName); if (className != null) { if (classLoader != null) { bd.setBeanClass(ClassUtils.forName(className, classLoader)); } else { bd.setBeanClassName(className); } } return bd; }创建了bean信息的承载实例后，便可以进行bean信息的各种属性解析了，parseBeanDefinitionAttributes()是对element元素属性的解析。
public AbstractBeanDefinition parseBeanDefinitionAttributes(Element ele, String beanName, @Nullable BeanDefinition containingBean, AbstractBeanDefinition bd) { if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) { error("Old 1.x 'singleton' attribute in use - upgrade to 'scope' declaration", ele); } else if (ele.hasAttribute(SCOPE_ATTRIBUTE)) { bd.setScope(ele.getAttribute(SCOPE_ATTRIBUTE)); } else if (containingBean != null) { // Take default from containing bean in case of an inner bean definition. bd.setScope(containingBean.getScope()); } if (ele.hasAttribute(ABSTRACT_ATTRIBUTE)) { bd.setAbstract(TRUE_VALUE.equals(ele.getAttribute(ABSTRACT_ATTRIBUTE))); } String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE); if (DEFAULT_VALUE.equals(lazyInit)) { lazyInit = this.defaults.getLazyInit(); } bd.setLazyInit(TRUE_VALUE.equals(lazyInit)); String autowire = ele.getAttribute(AUTOWIRE_ATTRIBUTE); bd.setAutowireMode(getAutowireMode(autowire)); if (ele.hasAttribute(DEPENDS_ON_ATTRIBUTE)) { String dependsOn = ele.getAttribute(DEPENDS_ON_ATTRIBUTE); bd.setDependsOn(StringUtils.tokenizeToStringArray(dependsOn, MULTI_VALUE_ATTRIBUTE_DELIMITERS)); } String autowireCandidate = ele.getAttribute(AUTOWIRE_CANDIDATE_ATTRIBUTE); if ("".equals(autowireCandidate) || DEFAULT_VALUE.equals(autowireCandidate)) { String candidatePattern = this.defaults.getAutowireCandidates(); if (candidatePattern != null) { String[] patterns = StringUtils.commaDelimitedListToStringArray(candidatePattern); bd.setAutowireCandidate(PatternMatchUtils.simpleMatch(patterns, beanName)); } } else { bd.setAutowireCandidate(TRUE_VALUE.equals(autowireCandidate)); } if (ele.hasAttribute(PRIMARY_ATTRIBUTE)) { bd.setPrimary(TRUE_VALUE.equals(ele.getAttribute(PRIMARY_ATTRIBUTE))); } if (ele.hasAttribute(INIT_METHOD_ATTRIBUTE)) { String initMethodName = ele.getAttribute(INIT_METHOD_ATTRIBUTE); bd.setInitMethodName(initMethodName); } else if (this.defaults.getInitMethod() != null) { bd.setInitMethodName(this.defaults.getInitMethod()); bd.setEnforceInitMethod(false); } if (ele.hasAttribute(DESTROY_METHOD_ATTRIBUTE)) { String destroyMethodName = ele.getAttribute(DESTROY_METHOD_ATTRIBUTE); bd.setDestroyMethodName(destroyMethodName); } else if (this.defaults.getDestroyMethod() != null) { bd.setDestroyMethodName(this.defaults.getDestroyMethod()); bd.setEnforceDestroyMethod(false); } if (ele.hasAttribute(FACTORY_METHOD_ATTRIBUTE)) { bd.setFactoryMethodName(ele.getAttribute(FACTORY_METHOD_ATTRIBUTE)); } if (ele.hasAttribute(FACTORY_BEAN_ATTRIBUTE)) { bd.setFactoryBeanName(ele.getAttribute(FACTORY_BEAN_ATTRIBUTE)); } return bd; }由上述代码可以看出，spring完成了对所有bean的解析。
从下面代码看meta元素的使用：
<bean id="userService" class="com.taobao.UserService"> <meta key="key1" value="value1"/> </bean>meta元素只是UserService类的额外声明，不会出现类的属性中。meta信息的获取可以通过BeanDefinition的getAttribute(key)方法获取。
下面是对meta元素的解析：
public void parseMetaElements(Element ele, BeanMetadataAttributeAccessor attributeAccessor) { NodeList nl = ele.getChildNodes(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (isCandidateElement(node) && nodeNameEquals(node, META_ELEMENT)) { Element metaElement = (Element) node; String key = metaElement.getAttribute(KEY_ATTRIBUTE); String value = metaElement.getAttribute(VALUE_ATTRIBUTE); BeanMetadataAttribute attribute = new BeanMetadataAttribute(key, value); attribute.setSource(extractSource(metaElement)); attributeAccessor.addMetadataAttribute(attribute); } } }lookup-method成为获取器注入，它是一种特殊的方法注入，它把一个方法声明为返回某种类型的bean，但实际返回的bean是配置文件里配置的，这个方法可用在设计有些可插拔的功能上，解除程序依赖。
下面是lookup-method的解析代码：
/** * Parse lookup-override sub-elements of the given bean element. */ public void parseLookupOverrideSubElements(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, 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); } } }这个方法主要是对bean中replaced-method子元素的获取。replaced-method用于方法替换，它可以在运行时用新的方法替换现有的方法。与lookup-method不同，replaced-method不但可以动态地替换返回实体，还能动态更改原有方法逻辑。
/** * Parse replaced-method sub-elements of the given bean element. */ 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); } } }无论是lookup-method还是replaced-method，它们都构造了一个MethodOverride，并最终记录在AbstractBeanDefinition的methodOverrides属性中。
从上面代码可以分析，先提取了constructor-arg上必要的属性(index，type，name)，然后：
如果配置中制定了index属性，操作如下：
解析Constructor-arg的子元素；使用ConstructorArgumentValues.ValueHolder类型来封装解析出来的元素；将type、name和index属性一并封装在ConstructorArgumentValues.ValueHolder类型中，并添加至当前的BeanDefinition的constructorArgumentValues的indexedArgumentValues属性中。如果没有指定index属性，那么操作如下：
解析Constructor-arg的子元素；使用ConstructorArgumentValues.ValueHolder类型来封装解析出来的元素；将type、name和index属性一并封装在ConstructorArgumentValues.ValueHolder类型中，并添加至当前的BeanDefinition的constructorArgumentValues的genericArgumentValues属性中。下面是解析构造函数配置中子元素的过程：
public Object parsePropertyValue(Element ele, BeanDefinition bd, @Nullable 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; } } 略过description或者meta；提取constructor-arg上的ref和value属性，以便于根据规则验证正确性，其规则为在constructor-arg上不存在一下情况：同时既有ref属性又有value属性；存在ref属性或者value属性且又有子元素；ref属性的处理；使用RuntimeBeanReference封装对应的ref名称；value属性的处理；使用TypedStringValue封装；子元素封装；调用parsePropertySubElement(subElement, bd)封装；下面是parsePropertySubElement(subElement, bd)处理子元素的过程：
public Object parsePropertySubElement(Element ele, @Nullable BeanDefinition bd, @Nullable String defaultValueType) { if (!isDefaultNamespace(ele)) { return parseNestedCustomElement(ele, bd); } else if (nodeNameEquals(ele, BEAN_ELEMENT)) { BeanDefinitionHolder nestedBd = parseBeanDefinitionElement(ele, bd); if (nestedBd != null) { nestedBd = decorateBeanDefinitionIfRequired(ele, nestedBd, bd); } return nestedBd; } else if (nodeNameEquals(ele, REF_ELEMENT)) { // A generic reference to any name of any bean. String refName = ele.getAttribute(BEAN_REF_ATTRIBUTE); boolean toParent = false; if (!StringUtils.hasLength(refName)) { // A reference to the id of another bean in a parent context. refName = ele.getAttribute(PARENT_REF_ATTRIBUTE); toParent = true; if (!StringUtils.hasLength(refName)) { error("'bean' or 'parent' is required for <ref> element", ele); return null; } } if (!StringUtils.hasText(refName)) { error("<ref> element contains empty target attribute", ele); return null; } RuntimeBeanReference ref = new RuntimeBeanReference(refName, toParent); ref.setSource(extractSource(ele)); return ref; } else if (nodeNameEquals(ele, IDREF_ELEMENT)) { return parseIdRefElement(ele); } else if (nodeNameEquals(ele, VALUE_ELEMENT)) { return parseValueElement(ele, defaultValueType); } else if (nodeNameEquals(ele, NULL_ELEMENT)) { // It's a distinguished null value. Let's wrap it in a TypedStringValue // object in order to preserve the source location. TypedStringValue nullHolder = new TypedStringValue(null); nullHolder.setSource(extractSource(ele)); return nullHolder; } else if (nodeNameEquals(ele, ARRAY_ELEMENT)) { return parseArrayElement(ele, bd); } else if (nodeNameEquals(ele, LIST_ELEMENT)) { return parseListElement(ele, bd); } else if (nodeNameEquals(ele, SET_ELEMENT)) { return parseSetElement(ele, bd); } else if (nodeNameEquals(ele, MAP_ELEMENT)) { return parseMapElement(ele, bd); } else if (nodeNameEquals(ele, PROPS_ELEMENT)) { return parsePropsElement(ele); } else { error("Unknown property sub-element: [" + ele.getNodeName() + "]", ele); return null; } }具体过程如下：
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); } } }由上代码可以看出，先提取出所有property的子元素，再交给parsePropertyElement(Element ele, BeanDefinition bd)方法封装处理。
/** * Parse a property element. */ 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(); } }对于qualifier元素的获取，更多用的是注解方式，在使用spring进行自动注入时，spring匹配的候选bean数必须有且只有一个。当找不到匹配的bean时，将抛出BeanCreationException异常，并指出必须至少拥有一个匹配的bean。
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(); } }对XML文档的解析都保存到了GenericBeanDefinition中，XML中所有的配置都可以在GenericBeanDefinition找到相应的属性。
GenericBeanDefinition是AbstractBeanDefinition的子类，大部分通用属性都保存在AbstractBeanDefinition中。下面是AbstractBeanDefinition的类信息：
public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccessor implements BeanDefinition, Cloneable { /** * Constant for the default scope name: {@code ""}, equivalent to singleton * status unless overridden from a parent bean definition (if applicable). */ public static final String SCOPE_DEFAULT = ""; /** * Constant that indicates no autowiring at all. * @see #setAutowireMode */ public static final int AUTOWIRE_NO = AutowireCapableBeanFactory.AUTOWIRE_NO; /** * Constant that indicates autowiring bean properties by name. * @see #setAutowireMode */ public static final int AUTOWIRE_BY_NAME = AutowireCapableBeanFactory.AUTOWIRE_BY_NAME; /** * Constant that indicates autowiring bean properties by type. * @see #setAutowireMode */ public static final int AUTOWIRE_BY_TYPE = AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE; /** * Constant that indicates autowiring a constructor. * @see #setAutowireMode */ public static final int AUTOWIRE_CONSTRUCTOR = AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR; /** * Constant that indicates determining an appropriate autowire strategy * through introspection of the bean class. * @see #setAutowireMode * @deprecated as of Spring 3.0: If you are using mixed autowiring strategies, * use annotation-based autowiring for clearer demarcation of autowiring needs. */ @Deprecated public static final int AUTOWIRE_AUTODETECT = AutowireCapableBeanFactory.AUTOWIRE_AUTODETECT; /** * Constant that indicates no dependency check at all. * @see #setDependencyCheck */ public static final int DEPENDENCY_CHECK_NONE = 0; /** * Constant that indicates dependency checking for object references. * @see #setDependencyCheck */ public static final int DEPENDENCY_CHECK_OBJECTS = 1; /** * Constant that indicates dependency checking for "simple" properties. * @see #setDependencyCheck * @see org.springframework.beans.BeanUtils#isSimpleProperty */ public static final int DEPENDENCY_CHECK_SIMPLE = 2; /** * Constant that indicates dependency checking for all properties * (object references as well as "simple" properties). * @see #setDependencyCheck */ public static final int DEPENDENCY_CHECK_ALL = 3; /** * Constant that indicates the container should attempt to infer the * {@link #setDestroyMethodName destroy method name} for a bean as opposed to * explicit specification of a method name. The value {@value} is specifically * designed to include characters otherwise illegal in a method name, ensuring * no possibility of collisions with legitimately named methods having the same * name. * <p>Currently, the method names detected during destroy method inference * are "close" and "shutdown", if present on the specific bean class. */ public static final String INFER_METHOD = "(inferred)"; @Nullable private volatile Object beanClass; @Nullable private String scope = SCOPE_DEFAULT; private boolean abstractFlag = false; private boolean lazyInit = false; private int autowireMode = AUTOWIRE_NO; private int dependencyCheck = DEPENDENCY_CHECK_NONE; @Nullable private String[] dependsOn; private boolean autowireCandidate = true; private boolean primary = false; private final Map<String, AutowireCandidateQualifier> qualifiers = new LinkedHashMap<>(0); @Nullable private Supplier<?> instanceSupplier; private boolean nonPublicAccessAllowed = true; private boolean lenientConstructorResolution = true; @Nullable private String factoryBeanName; @Nullable private String factoryMethodName; private ConstructorArgumentValues constructorArgumentValues; private MutablePropertyValues propertyValues; private MethodOverrides methodOverrides = new MethodOverrides(); @Nullable private String initMethodName; @Nullable private String destroyMethodName; private boolean enforceInitMethod = true; private boolean enforceDestroyMethod = true; private boolean synthetic = false; private int role = BeanDefinition.ROLE_APPLICATION; @Nullable private String description; @Nullable private Resource resource; /** * Create a new AbstractBeanDefinition with default settings. */ protected AbstractBeanDefinition() { this(null, null); } /** * Create a new AbstractBeanDefinition with the given * constructor argument values and property values. */ protected AbstractBeanDefinition(@Nullable ConstructorArgumentValues cargs, @Nullable MutablePropertyValues pvs) { this.constructorArgumentValues = (cargs != null ? cargs : new ConstructorArgumentValues()); this.propertyValues = (pvs != null ? pvs : new MutablePropertyValues()); } /** * Create a new AbstractBeanDefinition as a deep copy of the given * bean definition. * @param original the original bean definition to copy from */ protected AbstractBeanDefinition(BeanDefinition original) { setParentName(original.getParentName()); setBeanClassName(original.getBeanClassName()); setScope(original.getScope()); setAbstract(original.isAbstract()); setLazyInit(original.isLazyInit()); setFactoryBeanName(original.getFactoryBeanName()); setFactoryMethodName(original.getFactoryMethodName()); this.constructorArgumentValues = new ConstructorArgumentValues(original.getConstructorArgumentValues()); this.propertyValues = new MutablePropertyValues(original.getPropertyValues()); setRole(original.getRole()); setSource(original.getSource()); copyAttributesFrom(original); if (original instanceof AbstractBeanDefinition) { AbstractBeanDefinition originalAbd = (AbstractBeanDefinition) original; if (originalAbd.hasBeanClass()) { setBeanClass(originalAbd.getBeanClass()); } setAutowireMode(originalAbd.getAutowireMode()); setDependencyCheck(originalAbd.getDependencyCheck()); setDependsOn(originalAbd.getDependsOn()); setAutowireCandidate(originalAbd.isAutowireCandidate()); setPrimary(originalAbd.isPrimary()); copyQualifiersFrom(originalAbd); setInstanceSupplier(originalAbd.getInstanceSupplier()); setNonPublicAccessAllowed(originalAbd.isNonPublicAccessAllowed()); setLenientConstructorResolution(originalAbd.isLenientConstructorResolution()); setMethodOverrides(new MethodOverrides(originalAbd.getMethodOverrides())); setInitMethodName(originalAbd.getInitMethodName()); setEnforceInitMethod(originalAbd.isEnforceInitMethod()); setDestroyMethodName(originalAbd.getDestroyMethodName()); setEnforceDestroyMethod(originalAbd.isEnforceDestroyMethod()); setSynthetic(originalAbd.isSynthetic()); setResource(originalAbd.getResource()); } else { setResourceDescription(original.getResourceDescription()); } } /** * Override settings in this bean definition (presumably a copied parent * from a parent-child inheritance relationship) from the given bean * definition (presumably the child). * <ul> * <li>Will override beanClass if specified in the given bean definition. * <li>Will always take {@code abstract}, {@code scope}, * {@code lazyInit}, {@code autowireMode}, {@code dependencyCheck}, * and {@code dependsOn} from the given bean definition. * <li>Will add {@code constructorArgumentValues}, {@code propertyValues}, * {@code methodOverrides} from the given bean definition to existing ones. * <li>Will override {@code factoryBeanName}, {@code factoryMethodName}, * {@code initMethodName}, and {@code destroyMethodName} if specified * in the given bean definition. * </ul> */ public void overrideFrom(BeanDefinition other) { if (StringUtils.hasLength(other.getBeanClassName())) { setBeanClassName(other.getBeanClassName()); } if (StringUtils.hasLength(other.getScope())) { setScope(other.getScope()); } setAbstract(other.isAbstract()); setLazyInit(other.isLazyInit()); if (StringUtils.hasLength(other.getFactoryBeanName())) { setFactoryBeanName(other.getFactoryBeanName()); } if (StringUtils.hasLength(other.getFactoryMethodName())) { setFactoryMethodName(other.getFactoryMethodName()); } getConstructorArgumentValues().addArgumentValues(other.getConstructorArgumentValues()); getPropertyValues().addPropertyValues(other.getPropertyValues()); setRole(other.getRole()); setSource(other.getSource()); copyAttributesFrom(other); if (other instanceof AbstractBeanDefinition) { AbstractBeanDefinition otherAbd = (AbstractBeanDefinition) other; if (otherAbd.hasBeanClass()) { setBeanClass(otherAbd.getBeanClass()); } setAutowireMode(otherAbd.getAutowireMode()); setDependencyCheck(otherAbd.getDependencyCheck()); setDependsOn(otherAbd.getDependsOn()); setAutowireCandidate(otherAbd.isAutowireCandidate()); setPrimary(otherAbd.isPrimary()); copyQualifiersFrom(otherAbd); setInstanceSupplier(otherAbd.getInstanceSupplier()); setNonPublicAccessAllowed(otherAbd.isNonPublicAccessAllowed()); setLenientConstructorResolution(otherAbd.isLenientConstructorResolution()); getMethodOverrides().addOverrides(otherAbd.getMethodOverrides()); if (otherAbd.getInitMethodName() != null) { setInitMethodName(otherAbd.getInitMethodName()); setEnforceInitMethod(otherAbd.isEnforceInitMethod()); } if (otherAbd.getDestroyMethodName() != null) { setDestroyMethodName(otherAbd.getDestroyMethodName()); setEnforceDestroyMethod(otherAbd.isEnforceDestroyMethod()); } setSynthetic(otherAbd.isSynthetic()); setResource(otherAbd.getResource()); } else { setResourceDescription(other.getResourceDescription()); } } /** * Apply the provided default values to this bean. * @param defaults the defaults to apply */ public void applyDefaults(BeanDefinitionDefaults defaults) { setLazyInit(defaults.isLazyInit()); setAutowireMode(defaults.getAutowireMode()); setDependencyCheck(defaults.getDependencyCheck()); setInitMethodName(defaults.getInitMethodName()); setEnforceInitMethod(false); setDestroyMethodName(defaults.getDestroyMethodName()); setEnforceDestroyMethod(false); } /** * Specify the bean class name of this bean definition. */ @Override public void setBeanClassName(@Nullable String beanClassName) { this.beanClass = beanClassName; } /** * Return the current bean class name of this bean definition. */ @Override @Nullable public String getBeanClassName() { Object beanClassObject = this.beanClass; if (beanClassObject instanceof Class) { return ((Class<?>) beanClassObject).getName(); } else { return (String) beanClassObject; } } /** * Specify the class for this bean. */ public void setBeanClass(@Nullable Class<?> beanClass) { this.beanClass = beanClass; } /** * Return the class of the wrapped bean, if already resolved. * @return the bean class, or {@code null} if none defined * @throws IllegalStateException if the bean definition does not define a bean class, * or a specified bean class name has not been resolved into an actual Class */ public Class<?> getBeanClass() throws IllegalStateException { Object beanClassObject = this.beanClass; if (beanClassObject == null) { throw new IllegalStateException("No bean class specified on bean definition"); } if (!(beanClassObject instanceof Class)) { throw new IllegalStateException( "Bean class name [" + beanClassObject + "] has not been resolved into an actual Class"); } return (Class<?>) beanClassObject; } /** * Return whether this definition specifies a bean class. */ public boolean hasBeanClass() { return (this.beanClass instanceof Class); } /** * Determine the class of the wrapped bean, resolving it from a * specified class name if necessary. Will also reload a specified * Class from its name when called with the bean class already resolved. * @param classLoader the ClassLoader to use for resolving a (potential) class name * @return the resolved bean class * @throws ClassNotFoundException if the class name could be resolved */ @Nullable public Class<?> resolveBeanClass(@Nullable ClassLoader classLoader) throws ClassNotFoundException { String className = getBeanClassName(); if (className == null) { return null; } Class<?> resolvedClass = ClassUtils.forName(className, classLoader); this.beanClass = resolvedClass; return resolvedClass; } /** * Set the name of the target scope for the bean. * <p>The default is singleton status, although this is only applied once * a bean definition becomes active in the containing factory. A bean * definition may eventually inherit its scope from a parent bean definition. * For this reason, the default scope name is an empty string (i.e., {@code ""}), * with singleton status being assumed until a resolved scope is set. * @see #SCOPE_SINGLETON * @see #SCOPE_PROTOTYPE */ @Override public void setScope(@Nullable String scope) { this.scope = scope; } /** * Return the name of the target scope for the bean. */ @Override @Nullable public String getScope() { return this.scope; } /** * Return whether this a <b>Singleton</b>, with a single shared instance * returned from all calls. * @see #SCOPE_SINGLETON */ @Override public boolean isSingleton() { return SCOPE_SINGLETON.equals(scope) || SCOPE_DEFAULT.equals(scope); } /** * Return whether this a <b>Prototype</b>, with an independent instance * returned for each call. * @see #SCOPE_PROTOTYPE */ @Override public boolean isPrototype() { return SCOPE_PROTOTYPE.equals(scope); } /** * Set if this bean is "abstract", i.e. not meant to be instantiated itself but * rather just serving as parent for concrete child bean definitions. * <p>Default is "false". Specify true to tell the bean factory to not try to * instantiate that particular bean in any case. */ public void setAbstract(boolean abstractFlag) { this.abstractFlag = abstractFlag; } /** * Return whether this bean is "abstract", i.e. not meant to be instantiated * itself but rather just serving as parent for concrete child bean definitions. */ @Override public boolean isAbstract() { return this.abstractFlag; } /** * Set whether this bean should be lazily initialized. * <p>If {@code false}, the bean will get instantiated on startup by bean * factories that perform eager initialization of singletons. */ @Override public void setLazyInit(boolean lazyInit) { this.lazyInit = lazyInit; } /** * Return whether this bean should be lazily initialized, i.e. not * eagerly instantiated on startup. Only applicable to a singleton bean. */ @Override public boolean isLazyInit() { return this.lazyInit; } /** * Set the autowire mode. This determines whether any automagical detection * and setting of bean references will happen. Default is AUTOWIRE_NO, * which means there's no autowire. * @param autowireMode the autowire mode to set. * Must be one of the constants defined in this class. * @see #AUTOWIRE_NO * @see #AUTOWIRE_BY_NAME * @see #AUTOWIRE_BY_TYPE * @see #AUTOWIRE_CONSTRUCTOR * @see #AUTOWIRE_AUTODETECT */ public void setAutowireMode(int autowireMode) { this.autowireMode = autowireMode; } /** * Return the autowire mode as specified in the bean definition. */ public int getAutowireMode() { return this.autowireMode; } /** * Return the resolved autowire code, * (resolving AUTOWIRE_AUTODETECT to AUTOWIRE_CONSTRUCTOR or AUTOWIRE_BY_TYPE). * @see #AUTOWIRE_AUTODETECT * @see #AUTOWIRE_CONSTRUCTOR * @see #AUTOWIRE_BY_TYPE */ public int getResolvedAutowireMode() { if (this.autowireMode == AUTOWIRE_AUTODETECT) { // Work out whether to apply setter autowiring or constructor autowiring. // If it has a no-arg constructor it's deemed to be setter autowiring, // otherwise we'll try constructor autowiring. Constructor<?>[] constructors = getBeanClass().getConstructors(); for (Constructor<?> constructor : constructors) { if (constructor.getParameterCount() == 0) { return AUTOWIRE_BY_TYPE; } } return AUTOWIRE_CONSTRUCTOR; } else { return this.autowireMode; } } /** * Set the dependency check code. * @param dependencyCheck the code to set. * Must be one of the four constants defined in this class. * @see #DEPENDENCY_CHECK_NONE * @see #DEPENDENCY_CHECK_OBJECTS * @see #DEPENDENCY_CHECK_SIMPLE * @see #DEPENDENCY_CHECK_ALL */ public void setDependencyCheck(int dependencyCheck) { this.dependencyCheck = dependencyCheck; } /** * Return the dependency check code. */ public int getDependencyCheck() { return this.dependencyCheck; } /** * Set the names of the beans that this bean depends on being initialized. * The bean factory will guarantee that these beans get initialized first. * <p>Note that dependencies are normally expressed through bean properties or * constructor arguments. This property should just be necessary for other kinds * of dependencies like statics (*ugh*) or database preparation on startup. */ @Override public void setDependsOn(@Nullable String... dependsOn) { this.dependsOn = dependsOn; } /** * Return the bean names that this bean depends on. */ @Override @Nullable public String[] getDependsOn() { return this.dependsOn; } /** * Set whether this bean is a candidate for getting autowired into some other bean. * <p>Note that this flag is designed to only affect type-based autowiring. * It does not affect explicit references by name, which will get resolved even * if the specified bean is not marked as an autowire candidate. As a consequence, * autowiring by name will nevertheless inject a bean if the name matches. * @see #AUTOWIRE_BY_TYPE * @see #AUTOWIRE_BY_NAME */ @Override public void setAutowireCandidate(boolean autowireCandidate) { this.autowireCandidate = autowireCandidate; } /** * Return whether this bean is a candidate for getting autowired into some other bean. */ @Override public boolean isAutowireCandidate() { return this.autowireCandidate; } /** * Set whether this bean is a primary autowire candidate. * <p>If this value is {@code true} for exactly one bean among multiple * matching candidates, it will serve as a tie-breaker. */ @Override public void setPrimary(boolean primary) { this.primary = primary; } /** * Return whether this bean is a primary autowire candidate. */ @Override public boolean isPrimary() { return this.primary; } /** * Register a qualifier to be used for autowire candidate resolution, * keyed by the qualifier's type name. * @see AutowireCandidateQualifier#getTypeName() */ public void addQualifier(AutowireCandidateQualifier qualifier) { this.qualifiers.put(qualifier.getTypeName(), qualifier); } /** * Return whether this bean has the specified qualifier. */ public boolean hasQualifier(String typeName) { return this.qualifiers.keySet().contains(typeName); } /** * Return the qualifier mapped to the provided type name. */ @Nullable public AutowireCandidateQualifier getQualifier(String typeName) { return this.qualifiers.get(typeName); } /** * Return all registered qualifiers. * @return the Set of {@link AutowireCandidateQualifier} objects. */ public Set<AutowireCandidateQualifier> getQualifiers() { return new LinkedHashSet<>(this.qualifiers.values()); } /** * Copy the qualifiers from the supplied AbstractBeanDefinition to this bean definition. * @param source the AbstractBeanDefinition to copy from */ public void copyQualifiersFrom(AbstractBeanDefinition source) { Assert.notNull(source, "Source must not be null"); this.qualifiers.putAll(source.qualifiers); } /** * Specify a callback for creating an instance of the bean, * as an alternative to a declaratively specified factory method. * <p>If such a callback is set, it will override any other constructor * or factory method metadata. However, bean property population and * potential annotation-driven injection will still apply as usual. * @since 5.0 * @see #setConstructorArgumentValues(ConstructorArgumentValues) * @see #setPropertyValues(MutablePropertyValues) */ public void setInstanceSupplier(@Nullable Supplier<?> instanceSupplier) { this.instanceSupplier = instanceSupplier; } /** * Return a callback for creating an instance of the bean, if any. * @since 5.0 */ @Nullable public Supplier<?> getInstanceSupplier() { return this.instanceSupplier; } /** * Specify whether to allow access to non-public constructors and methods, * for the case of externalized metadata pointing to those. The default is * {@code true}; switch this to {@code false} for public access only. * <p>This applies to constructor resolution, factory method resolution, * and also init/destroy methods. Bean property accessors have to be public * in any case and are not affected by this setting. * <p>Note that annotation-driven configuration will still access non-public * members as far as they have been annotated. This setting applies to * externalized metadata in this bean definition only. */ public void setNonPublicAccessAllowed(boolean nonPublicAccessAllowed) { this.nonPublicAccessAllowed = nonPublicAccessAllowed; } /** * Return whether to allow access to non-public constructors and methods. */ public boolean isNonPublicAccessAllowed() { return this.nonPublicAccessAllowed; } /** * Specify whether to resolve constructors in lenient mode ({@code true}, * which is the default) or to switch to strict resolution (throwing an exception * in case of ambiguous constructors that all match when converting the arguments, * whereas lenient mode would use the one with the 'closest' type matches). */ public void setLenientConstructorResolution(boolean lenientConstructorResolution) { this.lenientConstructorResolution = lenientConstructorResolution; } /** * Return whether to resolve constructors in lenient mode or in strict mode. */ public boolean isLenientConstructorResolution() { return this.lenientConstructorResolution; } /** * Specify the factory bean to use, if any. * This the name of the bean to call the specified factory method on. * @see #setFactoryMethodName */ @Override public void setFactoryBeanName(@Nullable String factoryBeanName) { this.factoryBeanName = factoryBeanName; } /** * Return the factory bean name, if any. */ @Override @Nullable public String getFactoryBeanName() { return this.factoryBeanName; } /** * Specify a factory method, if any. This method will be invoked with * constructor arguments, or with no arguments if none are specified. * The method will be invoked on the specified factory bean, if any, * or otherwise as a static method on the local bean class. * @see #setFactoryBeanName * @see #setBeanClassName */ @Override public void setFactoryMethodName(@Nullable String factoryMethodName) { this.factoryMethodName = factoryMethodName; } /** * Return a factory method, if any. */ @Override @Nullable public String getFactoryMethodName() { return this.factoryMethodName; } /** * Specify constructor argument values for this bean. */ public void setConstructorArgumentValues(@Nullable ConstructorArgumentValues constructorArgumentValues) { this.constructorArgumentValues = (constructorArgumentValues != null ? constructorArgumentValues : new ConstructorArgumentValues()); } /** * Return constructor argument values for this bean (never {@code null}). */ @Override public ConstructorArgumentValues getConstructorArgumentValues() { return this.constructorArgumentValues; } /** * Return if there are constructor argument values defined for this bean. */ public boolean hasConstructorArgumentValues() { return !this.constructorArgumentValues.isEmpty(); } /** * Specify property values for this bean, if any. */ public void setPropertyValues(@Nullable MutablePropertyValues propertyValues) { this.propertyValues = (propertyValues != null ? propertyValues : new MutablePropertyValues()); } /** * Return property values for this bean (never {@code null}). */ @Override public MutablePropertyValues getPropertyValues() { return this.propertyValues; } /** * Specify method overrides for the bean, if any. */ public void setMethodOverrides(@Nullable MethodOverrides methodOverrides) { this.methodOverrides = (methodOverrides != null ? methodOverrides : new MethodOverrides()); } /** * Return information about methods to be overridden by the IoC * container. This will be empty if there are no method overrides. * <p>Never returns {@code null}. */ public MethodOverrides getMethodOverrides() { return this.methodOverrides; } /** * Set the name of the initializer method. * <p>The default is {@code null} in which case there is no initializer method. */ public void setInitMethodName(@Nullable String initMethodName) { this.initMethodName = initMethodName; } /** * Return the name of the initializer method. */ @Nullable public String getInitMethodName() { return this.initMethodName; } /** * Specify whether or not the configured init method is the default. * <p>The default value is {@code false}. * @see #setInitMethodName */ public void setEnforceInitMethod(boolean enforceInitMethod) { this.enforceInitMethod = enforceInitMethod; } /** * Indicate whether the configured init method is the default. * @see #getInitMethodName() */ public boolean isEnforceInitMethod() { return this.enforceInitMethod; } /** * Set the name of the destroy method. * <p>The default is {@code null} in which case there is no destroy method. */ public void setDestroyMethodName(@Nullable String destroyMethodName) { this.destroyMethodName = destroyMethodName; } /** * Return the name of the destroy method. */ @Nullable public String getDestroyMethodName() { return this.destroyMethodName; } /** * Specify whether or not the configured destroy method is the default. * <p>The default value is {@code false}. * @see #setDestroyMethodName */ public void setEnforceDestroyMethod(boolean enforceDestroyMethod) { this.enforceDestroyMethod = enforceDestroyMethod; } /** * Indicate whether the configured destroy method is the default. * @see #getDestroyMethodName */ public boolean isEnforceDestroyMethod() { return this.enforceDestroyMethod; } /** * Set whether this bean definition is 'synthetic', that is, not defined * by the application itself (for example, an infrastructure bean such * as a helper for auto-proxying, created through {@code <aop:config>}). */ public void setSynthetic(boolean synthetic) { this.synthetic = synthetic; } /** * Return whether this bean definition is 'synthetic', that is, * not defined by the application itself. */ public boolean isSynthetic() { return this.synthetic; } /** * Set the role hint for this {@code BeanDefinition}. */ public void setRole(int role) { this.role = role; } /** * Return the role hint for this {@code BeanDefinition}. */ @Override public int getRole() { return this.role; } /** * Set a human-readable description of this bean definition. */ public void setDescription(@Nullable String description) { this.description = description; } /** * Return a human-readable description of this bean definition. */ @Override @Nullable public String getDescription() { return this.description; } /** * Set the resource that this bean definition came from * (for the purpose of showing context in case of errors). */ public void setResource(@Nullable Resource resource) { this.resource = resource; } /** * Return the resource that this bean definition came from. */ @Nullable public Resource getResource() { return this.resource; } /** * Set a description of the resource that this bean definition * came from (for the purpose of showing context in case of errors). */ public void setResourceDescription(@Nullable String resourceDescription) { this.resource = (resourceDescription != null ? new DescriptiveResource(resourceDescription) : null); } /** * Return a description of the resource that this bean definition * came from (for the purpose of showing context in case of errors). */ @Override @Nullable public String getResourceDescription() { return (this.resource != null ? this.resource.getDescription() : null); } /** * Set the originating (e.g. decorated) BeanDefinition, if any. */ public void setOriginatingBeanDefinition(BeanDefinition originatingBd) { this.resource = new BeanDefinitionResource(originatingBd); } /** * Return the originating BeanDefinition, or {@code null} if none. * Allows for retrieving the decorated bean definition, if any. * <p>Note that this method returns the immediate originator. Iterate through the * originator chain to find the original BeanDefinition as defined by the user. */ @Override @Nullable public BeanDefinition getOriginatingBeanDefinition() { return (this.resource instanceof BeanDefinitionResource ? ((BeanDefinitionResource) this.resource).getBeanDefinition() : null); } /** * Validate this bean definition. * @throws BeanDefinitionValidationException in case of validation failure */ public void validate() throws BeanDefinitionValidationException { if (!getMethodOverrides().isEmpty() && getFactoryMethodName() != null) { throw new BeanDefinitionValidationException( "Cannot combine static factory method with method overrides: " + "the static factory method must create the instance"); } if (hasBeanClass()) { prepareMethodOverrides(); } } /** * Validate and prepare the method overrides defined for this bean. * Checks for existence of a method with the specified name. * @throws BeanDefinitionValidationException in case of validation failure */ public void prepareMethodOverrides() throws BeanDefinitionValidationException { // Check that lookup methods exists. MethodOverrides methodOverrides = getMethodOverrides(); if (!methodOverrides.isEmpty()) { Set<MethodOverride> overrides = methodOverrides.getOverrides(); synchronized (overrides) { for (MethodOverride mo : overrides) { prepareMethodOverride(mo); } } } } /** * Validate and prepare the given method override. * Checks for existence of a method with the specified name, * marking it as not overloaded if none found. * @param mo the MethodOverride object to validate * @throws BeanDefinitionValidationException in case of validation failure */ protected void prepareMethodOverride(MethodOverride mo) throws BeanDefinitionValidationException { int count = ClassUtils.getMethodCountForName(getBeanClass(), mo.getMethodName()); if (count == 0) { throw new BeanDefinitionValidationException( "Invalid method override: no method with name '" + mo.getMethodName() + "' on class [" + getBeanClassName() + "]"); } else if (count == 1) { // Mark override as not overloaded, to avoid the overhead of arg type checking. mo.setOverloaded(false); } } /** * Public declaration of Object's {@code clone()} method. * Delegates to {@link #cloneBeanDefinition()}. * @see Object#clone() */ @Override public Object clone() { return cloneBeanDefinition(); } /** * Clone this bean definition. * To be implemented by concrete subclasses. * @return the cloned bean definition object */ public abstract AbstractBeanDefinition cloneBeanDefinition(); @Override public boolean equals(Object other) { if (this == other) { return true; } if (!(other instanceof AbstractBeanDefinition)) { return false; } AbstractBeanDefinition that = (AbstractBeanDefinition) other; if (!ObjectUtils.nullSafeEquals(getBeanClassName(), that.getBeanClassName())) return false; if (!ObjectUtils.nullSafeEquals(this.scope, that.scope)) return false; if (this.abstractFlag != that.abstractFlag) return false; if (this.lazyInit != that.lazyInit) return false; if (this.autowireMode != that.autowireMode) return false; if (this.dependencyCheck != that.dependencyCheck) return false; if (!Arrays.equals(this.dependsOn, that.dependsOn)) return false; if (this.autowireCandidate != that.autowireCandidate) return false; if (!ObjectUtils.nullSafeEquals(this.qualifiers, that.qualifiers)) return false; if (this.primary != that.primary) return false; if (this.nonPublicAccessAllowed != that.nonPublicAccessAllowed) return false; if (this.lenientConstructorResolution != that.lenientConstructorResolution) return false; if (!ObjectUtils.nullSafeEquals(this.constructorArgumentValues, that.constructorArgumentValues)) return false; if (!ObjectUtils.nullSafeEquals(this.propertyValues, that.propertyValues)) return false; if (!ObjectUtils.nullSafeEquals(this.methodOverrides, that.methodOverrides)) return false; if (!ObjectUtils.nullSafeEquals(this.factoryBeanName, that.factoryBeanName)) return false; if (!ObjectUtils.nullSafeEquals(this.factoryMethodName, that.factoryMethodName)) return false; if (!ObjectUtils.nullSafeEquals(this.initMethodName, that.initMethodName)) return false; if (this.enforceInitMethod != that.enforceInitMethod) return false; if (!ObjectUtils.nullSafeEquals(this.destroyMethodName, that.destroyMethodName)) return false; if (this.enforceDestroyMethod != that.enforceDestroyMethod) return false; if (this.synthetic != that.synthetic) return false; if (this.role != that.role) return false; return super.equals(other); } @Override public int hashCode() { int hashCode = ObjectUtils.nullSafeHashCode(getBeanClassName()); hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.scope); hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.constructorArgumentValues); hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.propertyValues); hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.factoryBeanName); hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.factoryMethodName); hashCode = 29 * hashCode + super.hashCode(); return hashCode; } @Override public String toString() { StringBuilder sb = new StringBuilder("class ["); sb.append(getBeanClassName()).append("]"); sb.append("; scope=").append(this.scope); sb.append("; abstract=").append(this.abstractFlag); sb.append("; lazyInit=").append(this.lazyInit); sb.append("; autowireMode=").append(this.autowireMode); sb.append("; dependencyCheck=").append(this.dependencyCheck); sb.append("; autowireCandidate=").append(this.autowireCandidate); sb.append("; primary=").append(this.primary); sb.append("; factoryBeanName=").append(this.factoryBeanName); sb.append("; factoryMethodName=").append(this.factoryMethodName); sb.append("; initMethodName=").append(this.initMethodName); sb.append("; destroyMethodName=").append(this.destroyMethodName); if (this.resource != null) { sb.append("; defined in ").append(this.resource.getDescription()); } return sb.toString(); } }完成了默认标签的解析后，还需要解析自定义的标签元素。再来看看默认标签解析函数的起始函数：
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); if (bdHolder != null) { //若存在默认标签的子节点下再有自定义属性，还需要再次对自定义标签进行解析 bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // Register the final decorated instance. BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry()); } catch (BeanDefinitionStoreException ex) { getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, ex); } // Send registration event. getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder)); } }bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder)代码就是对类似下面的标签再次进行对自定义标签的解析并重新封装到bhHolder实例中。
<bean id="userService" class="com.taobao.UserService"> <myuser username="aa"></myuser> </bean>spring中对bean的解析分为默认类型的解析和自定义类型的解析。
由上<myuser></myuser>出现在<bean>中，而不是作为单独的<bean>出现，因为它其实是作为<bean>的属性出现。
下面来看看delegate.decorateBeanDefinitionIfRequired(ele, bdHolder)的方法实现：
public BeanDefinitionHolder decorateBeanDefinitionIfRequired(Element ele, BeanDefinitionHolder definitionHolder) { return decorateBeanDefinitionIfRequired(ele, definitionHolder, null); }有上面的代码可以看见第三个参数为null，这个参数是传父类的bean，当对某个嵌套配置进行分析时，这里需要传递父类beanDefinition。这里传递的参数视为了使用父类的scope属性，以备没有设置scope时默认使用父类的属性，这里分析的是顶层配置，所以传递null。
public BeanDefinitionHolder decorateBeanDefinitionIfRequired( Element ele, BeanDefinitionHolder definitionHolder, @Nullable BeanDefinition containingBd) { BeanDefinitionHolder finalDefinition = definitionHolder; // Decorate based on custom attributes first. NamedNodeMap attributes = ele.getAttributes(); for (int i = 0; i < attributes.getLength(); i++) { Node node = attributes.item(i); finalDefinition = decorateIfRequired(node, finalDefinition, containingBd); } // Decorate based on custom nested elements. 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; }在上面代码中可以看到函数又调用了decorateIfRequired()函数对元素属性和子节点处理：
public BeanDefinitionHolder decorateIfRequired( Node node, BeanDefinitionHolder originalDef, @Nullable BeanDefinition containingBd) { String namespaceUri = getNamespaceURI(node); if (namespaceUri != null && !isDefaultNamespace(namespaceUri)) { NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri); if (handler != null) { BeanDefinitionHolder decorated = handler.decorate(node, originalDef, new ParserContext(this.readerContext, this, containingBd)); if (decorated != null) { return decorated; } } else if (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; }上述代码可以看出，首先获取属性或者元素的命名空间，以此来判断该元素或者属性是否适用于自定义标签的解析条件，找出自定义类型所对应的NamespaceHandler并进一步解析。
decorateBeanDefinitionIfRequired(ele, bdHolder)的作用：它对程序默认的标签的处理是直接略过，只对自定义标签进行处理，在方法中实现了寻找自定义标签并根据自定义标签寻找命名空间处理器，并进行进一步处理。
解析完BeanDefinition，就开始注册BeanDefinition了，调用BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry())。
public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { // Register bean definition under primary name. String beanName = definitionHolder.getBeanName(); registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); // Register aliases for bean name, if any. String[] aliases = definitionHolder.getAliases(); if (aliases != null) { for (String alias : aliases) { registry.registerAlias(beanName, alias); } } }从上面代码可以看出，解析出来的BeanDefinition都会注册到BeanDefinitionRegistry中，对BeanDefinition的注册包括beanName以及alias别名的注册。
通过beanName注册BeanDefinition：DefaultListableBeanFactory类中的registerBeanDefinition()方法。
@Override public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { Assert.hasText(beanName, "Bean name must not be empty"); Assert.notNull(beanDefinition, "BeanDefinition must not be null"); if (beanDefinition instanceof AbstractBeanDefinition) { try { ((AbstractBeanDefinition) beanDefinition).validate(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", ex); } } BeanDefinition oldBeanDefinition; oldBeanDefinition = this.beanDefinitionMap.get(beanName); if (oldBeanDefinition != null) { if (!isAllowBeanDefinitionOverriding()) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName + "': There is already [" + oldBeanDefinition + "] bound."); } else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) { // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE if (this.logger.isWarnEnabled()) { this.logger.warn("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else if (!beanDefinition.equals(oldBeanDefinition)) { if (this.logger.isInfoEnabled()) { this.logger.info("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else { if (this.logger.isDebugEnabled()) { this.logger.debug("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } this.beanDefinitionMap.put(beanName, beanDefinition); } else { if (hasBeanCreationStarted()) { // Cannot modify startup-time collection elements anymore (for stable iteration) synchronized (this.beanDefinitionMap) { this.beanDefinitionMap.put(beanName, beanDefinition); List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1); updatedDefinitions.addAll(this.beanDefinitionNames); updatedDefinitions.add(beanName); this.beanDefinitionNames = updatedDefinitions; if (this.manualSingletonNames.contains(beanName)) { Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames); updatedSingletons.remove(beanName); this.manualSingletonNames = updatedSingletons; } } } else { // Still in startup registration phase this.beanDefinitionMap.put(beanName, beanDefinition); this.beanDefinitionNames.add(beanName); this.manualSingletonNames.remove(beanName); } this.frozenBeanDefinitionNames = null; } if (oldBeanDefinition != null || containsSingleton(beanName)) { resetBeanDefinition(beanName); } }由上述代码可以看出对于bean的注册处理方式，主要有一下步骤：
对AbstractBeanDefiniton的校验。这里主要是针对AbstractBeanDefiniton的methodOverrides属性；对已注册beanName的情况的处理。如果设置了不允许bean的覆盖，则需要抛出异常，否则直接覆盖；加入map缓存；清除解析之前留下的对应beanName的缓存。
通过别名注册BeanDefinition：
public void registerAlias(String name, String alias) { Assert.hasText(name, "'name' must not be empty"); Assert.hasText(alias, "'alias' must not be empty"); if (alias.equals(name)) { this.aliasMap.remove(alias); } else { String registeredName = this.aliasMap.get(alias); if (registeredName != null) { if (registeredName.equals(name)) { // An existing alias - no need to re-register return; } if (!allowAliasOverriding()) { throw new IllegalStateException("Cannot register alias '" + alias + "' for name '" + name + "': It is already registered for name '" + registeredName + "'."); } } checkForAliasCircle(name, alias); this.aliasMap.put(alias, name); } } alias若与beanName相同情况处理。若alias与beanName并名称相同则不需要处理并删除原有alias；alias覆盖处理。若aliasName已经使用并已经指向了另一个beanName则需要用户的设置进行处理；alias循环检查。当A->B存在时，若再次出现A->C->B时候则会抛出异常。注册alias。通过getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder))完成注册完成事件的通知。这里的实现为扩展，当程序开发人员需要对注册BeanDefinition事件进行监听时可以通过注册监听器方式将处理逻辑写入监听器中，目前spring没有对此进行任何逻辑处理。
在解析<import>标签是，spring做了以下步骤处理：
获取resource属性所表示的路径；解析路径中的系统属性，格式如"${user.dir}"；判定location是绝对路径还是相对路径；如果是绝对路径则递归调用bean的解析过程，进行另一侧解析；如果是相对路径则计算出绝对路径并进行解析；通知监听器，解析完成。
对嵌入的<beans>标签的解析是通过递归调用解析<beans>方法的过程。
