源代码分析，是一件既痛苦又快乐的事情，看别人写的代码是通过的，但当你能够看明白的时候，相信快乐也会随之而来，为了减少痛苦，更快的带来快乐，
本文以spring框架的XmlBeanFactory为入手点进行分析
首先来打开该类的代码，我们将看到如下代码：
1 public class XmlBeanFactory extends DefaultListableBeanFactory {
2
3 private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);
4
5 public XmlBeanFactory(Resource resource) throws BeansException {
6 this(resource, null);
7 }
8
9 public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
10 super(parentBeanFactory);
11 this.reader.loadBeanDefinitions(resource);
12 }
13
14 }这个类的代码很简单，一个成员对象加两个构造函数，从这里我们可以看出，最重要的地方在于最后一个构造函数：
1 public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
2 super(parentBeanFactory);
3 this.reader.loadBeanDefinitions(resource);
4 }第一句就是将父亲工厂交给父类的构造函数，
实际上最后也就是把父工厂保存到类的parentBeanFactory成员对象中，这个对象是在AbstractBeanFactory抽象类中定义的，而这个父工厂也会一直传递到该抽象类进行保存。
第二句就是整个类中最重要的地方了，顾名思义，它的目的是通过XmlBeanDefinitionReader这个XML的Reader从资源resource中（也就是你的配置文件）读取bean的定义。
接下来我们打开XmlBeanDefinitionReader的loadBeanDefinitions方法，我们可看到在这个方法里代码就一行，调用了一个同名不同参的方法，而参数是EncodedResource的一个实例，这个类实际上是Resource的一个包装类，用来保存资源的Encode的，
1 public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
2 return loadBeanDefinitions(new EncodedResource(resource));
3 }那接下来我们再看被调用的loadBeanDefinitions方法，
1 public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
2 Assert.notNull(encodedResource, "EncodedResource must not be null");
3 if (logger.isInfoEnabled()) {
4 logger.info("Loading XML bean definitions from " + encodedResource.getResource());
5 }
6
7 Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
8 if (currentResources == null) {
9 currentResources = new HashSet<EncodedResource>(4);
10 this.resourcesCurrentlyBeingLoaded.set(currentResources);
11 }
12 if (!currentResources.add(encodedResource)) {
13 throw new BeanDefinitionStoreException(
14 "Detected cyclic loading of " + encodedResource + " - check your import definitions!");
15 }
16 try {
17 InputStream inputStream = encodedResource.getResource().getInputStream();
18 try {
19 InputSource inputSource = new InputSource(inputStream);
20 if (encodedResource.getEncoding() != null) {
21 inputSource.setEncoding(encodedResource.getEncoding());
22 }
23 return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
24 }
25 finally {
26 inputStream.close();
27 }
28 }
29 catch (IOException ex) {
30 throw new BeanDefinitionStoreException(
31 "IOException parsing XML document from " + encodedResource.getResource(), ex);
32 }
33 finally {
34 currentResources.remove(encodedResource);
35 if (currentResources.isEmpty()) {
36 this.resourcesCurrentlyBeingLoaded.remove();
37 }
38 }
39 }这个方法里最主要的部分就是：
1 try {
2 InputStream inputStream = encodedResource.getResource().getInputStream();
3 try {
4 InputSource inputSource = new InputSource(inputStream);
5 if (encodedResource.getEncoding() != null) {
6 inputSource.setEncoding(encodedResource.getEncoding());
7 }
8 return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
9 }
10 finally {
11 inputStream.close();
12 }
13 }这里的目的是将资源包装成一个InputSource，连同Resource作为参数传递到doLoadBeanDefinitions方法
1 protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
2 throws BeanDefinitionStoreException {
3 try {
4 Document doc = doLoadDocument(inputSource, resource);
5 return registerBeanDefinitions(doc, resource);
6 }
7 catch (BeanDefinitionStoreException ex) {
8 throw ex;
9 }
10 catch (SAXParseException ex) {
11 throw new XmlBeanDefinitionStoreException(resource.getDescription(),
12 "Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
13 }
14 catch (SAXException ex) {
15 throw new XmlBeanDefinitionStoreException(resource.getDescription(),
16 "XML document from " + resource + " is invalid", ex);
17 }
18 catch (ParserConfigurationException ex) {
19 throw new BeanDefinitionStoreException(resource.getDescription(),
20 "Parser configuration exception parsing XML from " + resource, ex);
21 }
22 catch (IOException ex) {
23 throw new BeanDefinitionStoreException(resource.getDescription(),
24 "IOException parsing XML document from " + resource, ex);
25 }
26 catch (Throwable ex) {
27 throw new BeanDefinitionStoreException(resource.getDescription(),
28 "Unexpected exception parsing XML document from " + resource, ex);
29 }
30 }很遗憾,这个类没有什么实际作为,只有一些对异常的处理.把解析的逻辑委托给了doLoadDocument这个方法
然后调用registerBeanDefinitions方法,注册Bean的信息
1 protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
2 return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
3 getValidationModeForResource(resource), isNamespaceAware());
4 }就是为了将资源解释成为Document对象,这里不做详细解释，不了解的话请去看看关于JAXP的介绍。
1 public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
2 ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {
3
4 DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
5 if (logger.isDebugEnabled()) {
6 logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");
7 }
8 DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
9 return builder.parse(inputSource);
10 }来看看registerBeanDefinitions的实现 1 public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
2 BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
3 documentReader.setEnvironment(this.getEnvironment());
4 int countBefore = getRegistry().getBeanDefinitionCount();
5 documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
6 return getRegistry().getBeanDefinitionCount() - countBefore;
7 }在这里, 有一个BeanDefinitionDocumentReader接口, 实际上Spring对它有一个默认的实现类叫DefaultBeanDefinitionDocumentReader, 来看看它的家族
BeanDefinitionDocumentReader只有2个方法 ,
registerBeanDefinitions就是其中一个 1 public interface BeanDefinitionDocumentReader {
2
3 /**
4 * Set the Environment to use when reading bean definitions.
5 * <p>Used for evaluating profile information to determine whether a
6 * {@code <beans/>} document/element should be included or ignored.
7 */
8 void setEnvironment(Environment environment);
9
10 /**
11 * Read bean definitions from the given DOM document and
12 * register them with the registry in the given reader context.
13 * @param doc the DOM document
14 * @param readerContext the current context of the reader
15 * (includes the target registry and the resource being parsed)
16 * @throws BeanDefinitionStoreException in case of parsing errors
17 */
18 void registerBeanDefinitions(Document doc, XmlReaderContext readerContext)
19 throws BeanDefinitionStoreException;
20
21 }
该方法需要两个参数, 一个是Document模型,这个应该是我们读取配置文件获取到的, 另一个是XmlReaderContext对象, 我们在上面方法中看到是通过createReaderContext(resource)得到的, 那就看看具体如何得到
1 public XmlReaderContext createReaderContext(Resource resource) {
2 return new XmlReaderContext(resource, this.problemReporter, this.eventListener,
3 this.sourceExtractor, this, getNamespaceHandlerResolver());
4 } 能过构造函数new出来的, 且有一个重要参数resource
再继续来看DefaultBeanDefinitionDocumentReader对BeanDefinitionDocumentReader的registerBeanDefinitions方法实现
1 public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
2 this.readerContext = readerContext;
3 logger.debug("Loading bean definitions");
4 Element root = doc.getDocumentElement();
5 doRegisterBeanDefinitions(root);
6 }是的
1 protected void doRegisterBeanDefinitions(Element root) {
2 String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
3 if (StringUtils.hasText(profileSpec)) {
4 Assert.state(this.environment != null, "Environment must be set for evaluating profiles");
5 String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
6 profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
7 if (!this.environment.acceptsProfiles(specifiedProfiles)) {
8 return;
9 }
10 }
11
12 // Any nested <beans> elements will cause recursion in this method. In
13 // order to propagate and preserve <beans> default-* attributes correctly,
14 // keep track of the current (parent) delegate, which may be null. Create
15 // the new (child) delegate with a reference to the parent for fallback purposes,
16 // then ultimately reset this.delegate back to its original (parent) reference.
17 // this behavior emulates a stack of delegates without actually necessitating one.
18 BeanDefinitionParserDelegate parent = this.delegate;
19 this.delegate = createDelegate(this.readerContext, root, parent);
20
21 preProcessXml(root);
22 parseBeanDefinitions(root, this.delegate);
23 postProcessXml(root);
24
25 this.delegate = parent;
26 }嘿嘿, 开始解析Dom了哦, 其中主要是parseBeanDefinitions方法, 来看看具体是如何解析的
这里创建了一个XmlBeanDefinitionParser接口的实现，这个接口的具体类是DefaultXmlBeanDefinitionParser，这个接口很简单，只有registerBeanDefinitions一个方法，这个方法的作用也很明了，就是用来注册Bean的定义的，所以说类和方法的名字一定要起得有意义，这样可以让人一看就大概了解其作用，减少了很多阅读代码的痛苦。废话不多说，我们打开DefaultXmlBeanDefinitionParser的registerBeanDefinitions方法，这个类就是解释XML配置文件的核心类了，打开registerBeanDefinitions方法后我们看到如下代码：
1 protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
2 if (delegate.isDefaultNamespace(root)) {
3 NodeList nl = root.getChildNodes();
4 for (int i = 0; i < nl.getLength(); i++) {
5 Node node = nl.item(i);
6 if (node instanceof Element) {
7 Element ele = (Element) node;
8 if (delegate.isDefaultNamespace(ele)) {
9 parseDefaultElement(ele, delegate);
10 }
11 else {
12 delegate.parseCustomElement(ele);
13 }
14 }
15 }
16 }
17 else {
18 delegate.parseCustomElement(root);
19 }
20 } 看到了吧, 循环解析Domcument节点
parseDefaultElement方法和delegate的parseCustomElement方法
先来看parseDefaultElement方法
1 private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
2 if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
3 importBeanDefinitionResource(ele);
4 }
5 else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
6 processAliasRegistration(ele);
7 }
8 else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
9 processBeanDefinition(ele, delegate);
10 }
11 else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
12 // recurse
13 doRegisterBeanDefinitions(ele);
14 }
15 }看到这就很清楚了, 就是根据节点的名称作不同解析, 如我们Spring配置文件中常有以下几种配置
<import resource="classpath:xxx" />
<bean id="car" class="entity.CarFactoryBean">
<property name="carInfo" value="超级跑车,400,2000000" />
</bean>对<import>节点, 调用importBeanDefinitionResource方法解析, 此方法中, 又回到第一步读取配置文件并解析. 如此递归循环.
...
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
...对<alias>节点, 调用processAliasRegistration进行别名解析
...
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
...我们主要看对<bean>节点调用processBeanDefinition进行解析
...
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
...
processBeanDefinition: 1 protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
2 BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
3 if (bdHolder != null) {
4 bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
5 try {
6 // Register the final decorated instance.
7 BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
8 }
9 catch (BeanDefinitionStoreException ex) {
10 getReaderContext().error("Failed to register bean definition with name '" +
11 bdHolder.getBeanName() + "'", ele, ex);
12 }
13 // Send registration event.
14 getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
15 }
16 }嘿嘿, 又用到delegate对象了, 且调用它的parseBeanDefinitionElement方法, 返回一个BeanDefinitionHolder, 进去看它的parseBeanDefinitionElement方法
1 public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
2 return parseBeanDefinitionElement(ele, null);
3 }
parseBeanDefinitionElement
1 public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
2 String id = ele.getAttribute(ID_ATTRIBUTE);
3 String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
4 //解析id, name等属性,
5 List<String> aliases = new ArrayList<String>();
6 if (StringUtils.hasLength(nameAttr)) {
7 String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
8 aliases.addAll(Arrays.asList(nameArr));
9 }
10
11 String beanName = id;
12 if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
13 beanName = aliases.remove(0);
14 if (logger.isDebugEnabled()) {
15 logger.debug("No XML 'id' specified - using '" + beanName +
16 "' as bean name and " + aliases + " as aliases");
17 }
18 }
19 //并验证beanName是否唯一, 并将beanName保存在aliases中
20 if (containingBean == null) {
21 checkNameUniqueness(beanName, aliases, ele);
22 }
23 //解析bean定义本身，而不考虑名称或别名。可能返回null，如果bean定义的解析过程中出现的问题
24 AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
25 if (beanDefinition != null) {
26 if (!StringUtils.hasText(beanName)) {
27 try {
28 if (containingBean != null) {
29 beanName = BeanDefinitionReaderUtils.generateBeanName(
30 beanDefinition, this.readerContext.getRegistry(), true);
31 }
32 else {
33 beanName = this.readerContext.generateBeanName(beanDefinition);
34 // Register an alias for the plain bean class name, if still possible,
35 // if the generator returned the class name plus a suffix.
36 // This is expected for Spring 1.2/2.0 backwards compatibility.
37 String beanClassName = beanDefinition.getBeanClassName();
38 if (beanClassName != null &&
39 beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&
40 !this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
41 aliases.add(beanClassName);
42 }
43 }
44 if (logger.isDebugEnabled()) {
45 logger.debug("Neither XML 'id' nor 'name' specified - " +
46 "using generated bean name [" + beanName + "]");
47 }
48 }
49 catch (Exception ex) {
50 error(ex.getMessage(), ele);
51 return null;
52 }
53 }
54 String[] aliasesArray = StringUtils.toStringArray(aliases);
55 return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
56 }
57
58 return null;
59 } 可以看到, 在BeanDefinitionHolder中保存了BeanDefinition的定义
OK, 重头戏开始, 最经典的部分出现了, 请看parseBeanDefinitionElement方法
1 public AbstractBeanDefinition parseBeanDefinitionElement(
2 Element ele, String beanName, BeanDefinition containingBean) {
3
4 this.parseState.push(new BeanEntry(beanName));
5
6 String className = null;
7 if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
8 className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
9 }
10
11 try {
12 String parent = null;
13 if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
14 parent = ele.getAttribute(PARENT_ATTRIBUTE);
15 }
16 AbstractBeanDefinition bd = createBeanDefinition(className, parent);
17
18 parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
19 bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
20
21 parseMetaElements(ele, bd);
22 parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
23 parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
24
25 parseConstructorArgElements(ele, bd);
26 parsePropertyElements(ele, bd);
27 parseQualifierElements(ele, bd);
28
29 bd.setResource(this.readerContext.getResource());
30 bd.setSource(extractSource(ele));
31
32 return bd;
33 }
34 catch (ClassNotFoundException ex) {
35 error("Bean class [" + className + "] not found", ele, ex);
36 }
37 catch (NoClassDefFoundError err) {
38 error("Class that bean class [" + className + "] depends on not found", ele, err);
39 }
40 catch (Throwable ex) {
41 error("Unexpected failure during bean definition parsing", ele, ex);
42 }
43 finally {
44 this.parseState.pop();
45 }
46
47 return null;
48 }在这个方法中, 解析了bean的所有属性, 有最常用的class, scope, lazy-init等等. 并返回一个AbstractBeanDefinition实例. 至于具体怎么解析, 就只能进一步跟踪了, 不过既然到了这一步, 已经明白了它的基本原理, 具体实现就不作介绍
1 public static AbstractBeanDefinition createBeanDefinition(
2 String parentName, String className, ClassLoader classLoader) throws ClassNotFoundException {
3
4 GenericBeanDefinition bd = new GenericBeanDefinition();
5 bd.setParentName(parentName);
6 if (className != null) {
7 if (classLoader != null) {
8 bd.setBeanClass(ClassUtils.forName(className, classLoader));
9 }
10 else {
11 bd.setBeanClassName(className);
12 }
13 }
14 return bd;
15 } 这一步将节点解析成BeanDefinitionHolder对象, 再看看如何注册, 回到DefaultBeanDefinitionDocumentReader的processBeanDefinition方法
看到对解析到的bdHolder对象又做了decorateBeanDefinitionIfRequired操作, 来看看实现
1 public BeanDefinitionHolder decorateBeanDefinitionIfRequired(Element ele, BeanDefinitionHolder definitionHolder) {
2 return decorateBeanDefinitionIfRequired(ele, definitionHolder, null);
3 }decorateBeanDefinitionIfRequired 1 public BeanDefinitionHolder decorateBeanDefinitionIfRequired(
2 Element ele, BeanDefinitionHolder definitionHolder, BeanDefinition containingBd) {
3
4 BeanDefinitionHolder finalDefinition = definitionHolder;
5
6 // Decorate based on custom attributes first.
7 NamedNodeMap attributes = ele.getAttributes();
8 for (int i = 0; i < attributes.getLength(); i++) {
9 Node node = attributes.item(i);
10 finalDefinition = decorateIfRequired(node, finalDefinition, containingBd);
11 }
12
13 // Decorate based on custom nested elements.
14 NodeList children = ele.getChildNodes();
15 for (int i = 0; i < children.getLength(); i++) {
16 Node node = children.item(i);
17 if (node.getNodeType() == Node.ELEMENT_NODE) {
18 finalDefinition = decorateIfRequired(node, finalDefinition, containingBd);
19 }
20 }
21 return finalDefinition;
22 }
这里关键就2行代码,主要是做一些合法性验证,比如 文件头,语法,属性的合法性,由于代码过长不一一解释,代码如下
1 public BeanDefinitionHolder decorateIfRequired(
2 Node node, BeanDefinitionHolder originalDef, BeanDefinition containingBd) {
3
4 String namespaceUri = getNamespaceURI(node);
5 if (!isDefaultNamespace(namespaceUri)) {
6 NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
7 if (handler != null) {
8 return handler.decorate(node, originalDef, new ParserContext(this.readerContext, this, containingBd));
9 }
10 else if (namespaceUri != null && namespaceUri.startsWith("http://www.springframework.org/")) {
11 error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", node);
12 }
13 else {
14 // A custom namespace, not to be handled by Spring - maybe "xml:...".
15 if (logger.isDebugEnabled()) {
16 logger.debug("No Spring NamespaceHandler found for XML schema namespace [" + namespaceUri + "]");
17 }
18 }
19 }
20 return originalDef;
21 }回到DefaultBeanDefinitionDocumentReade.processBeanDefinition这个方法 只行完delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);之后
接着调用了BeanDefinitionReaderUtils的registerBeanDefinition方法注册bdHolder, 来看看如何实现的
1 public static void registerBeanDefinition(
2 BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
3 throws BeanDefinitionStoreException {
4
5 // Register bean definition under primary name.
6 String beanName = definitionHolder.getBeanName();
7 registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
8
9 // Register aliases for bean name, if any.
10 String[] aliases = definitionHolder.getAliases();
11 if (aliases != null) {
12 for (String aliase : aliases) {
13 registry.registerAlias(beanName, aliase);
14 }
15 }
16 }
看吧, 又调用了BeanDefinitionRegistry的registerBeanDefinition方法, 跟踪之 (这个要看DefaultListableBeanFactory的实现)
1 public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
2 throws BeanDefinitionStoreException {
3
4 Assert.hasText(beanName, "Bean name must not be empty");
5 Assert.notNull(beanDefinition, "BeanDefinition must not be null");
6
7 if (beanDefinition instanceof AbstractBeanDefinition) {
8 try {
9 ((AbstractBeanDefinition) beanDefinition).validate();
10 }
11 catch (BeanDefinitionValidationException ex) {
12 throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
13 "Validation of bean definition failed", ex);
14 }
15 }
16
17 synchronized (this.beanDefinitionMap) {
18 BeanDefinition oldBeanDefinition = this.beanDefinitionMap.get(beanName);
19 if (oldBeanDefinition != null) {
20 if (!this.allowBeanDefinitionOverriding) {
21 throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
22 "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
23 "': There is already [" + oldBeanDefinition + "] bound.");
24 }
25 else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
26 // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
27 if (this.logger.isWarnEnabled()) {
28 this.logger.warn("Overriding user-defined bean definition for bean '" + beanName +
29 " with a framework-generated bean definition ': replacing [" +
30 oldBeanDefinition + "] with [" + beanDefinition + "]");
31 }
32 }
33 else {
34 if (this.logger.isInfoEnabled()) {
35 this.logger.info("Overriding bean definition for bean '" + beanName +
36 "': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
37 }
38 }
39 }
40 else {
41 this.beanDefinitionNames.add(beanName);
42 this.frozenBeanDefinitionNames = null;
43 }
44 this.beanDefinitionMap.put(beanName, beanDefinition);
45 }
46
47 resetBeanDefinition(beanName);
48 } 这里, 看到了一个最最重要的对象就是beanDefinitionMap, 这个map存放了所有的bean对象, 和我们通常讲的容器概念最为接近, getBean时实际是也是从这里领取对象, 相同的还有一个beanDefinitionNames, 但这个只保存bean的名称
完成上面之后, 还有一步操作beanFactory.registerAlias(beanName, aliases[i]);
这个实现实际是上AbstractBeanFactory抽象类所定义的
是不是特兴奋, 已经揭开它神秘的面纱了
定义 -> 定位 -> 装载 -> 注册 这几步已经完成了, 以后继续看Spring是如何创建bean及实例化的
多数内容来自:http://leayer.iteye.com/blog/806016