1.2 XmlBeanFactory的实例化

  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

 

 

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