Ioc容器beanDefinition－Spring 源码系列（1）

Ioc容器beanDefinition－Spring 源码系列（1）

目录：

Ioc容器beanDefinition－Spring 源码（1）

Ioc容器依赖注入－Spring 源码（2）


Ioc容器BeanPostProcessor－Spring 源码（3）

事件机制－Spring 源码（4）

AOP执行增强－Spring 源码系列（5）

1，理解控制反转

以前一直说着这个词，然后把它等于上ioc这个词，再等于上代码里一个bean里依赖了其他bean，不用new，用注解，用xml去描述，就可以了。能用就行了，实际理论的不管也不影响编码，其实能用了内心也是理解是怎么回事的，知识理论上说不好而已。
我觉得只要理解一个事情就好了，ioc所谓的控制翻转，它控制翻转的是什么？
依赖对象的获得被反转
　　把一个bean中对其他bean的依赖这个事提取出来，统一由一个容器管理，解耦了bean管理和业务的代码（工厂方法模式不就干这事嘛）
最后，Spring提供了一个IoC容器来管理对象的生命周期、依赖关系，这也是spring的最核心的基础组件。
其实控制反转也是一种设计模式，的确，从项目层面抽取了管理bean依赖关系，彻底解耦bean注入和业务代码，也是一种软件开发中的思想。



2，IoC容器
它要完成什么事？
通过解析bean依赖关系的描述，容器需要创建出项目中所有需要管理的bean，然后注入。
那么拆成打的两步：1，把依赖关系描述解析成bean；2，把bean注入
但是，既然是bean之间有依赖关系，当生产一个bean时，它依赖的bean也需要已经产生，所以在一个软件中，触发开始初始化容器的时候是把项目中用到的bean看成树结构的样子，然后一次递归的生产bean，注入。有点像目录结构遍历。
比如：A依赖B B依赖C，那么A生产时会触发B生产，然后触发C生产。
所以，我们阅读IoC源码时也会看到这样的实现。



3，IoC容器的实现

BeanFactory和ApplicationContext
BeanFactory是容器基础设计，ApplicationContext增加了针对企业软件一些扩展功能，应该说后者是前者的高级形态。

public interface BeanFactory {

/**
* 用来获取FactoryBean本身的转义符
*/
String FACTORY_BEAN_PREFIX = "&";

/**
* 获取容器维护的bean是用名称来指定的
*/
Object getBean(String name) throws BeansException;

<T> T getBean(String name, Class<T> requiredType) throws BeansException;

<T> T getBean(Class<T> requiredType) throws BeansException;

Object getBean(String name, Object... args) throws BeansException;

<T> T getBean(Class<T> requiredType, Object... args) throws BeansException;

/**
* 查看容器中是否包含指定name的bean
*/
boolean containsBean(String name);

/**
* 判断指定name的bean是否为单例
*/
boolean isSingleton(String name) throws NoSuchBeanDefinitionException;

/**
* 判断指定name的bean是否为多例
*/
boolean isPrototype(String name) throws NoSuchBeanDefinitionException;

boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;

boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException;

Class<?> getType(String name) throws NoSuchBeanDefinitionException;

/**
* 获得bean的所有别名
*/
String[] getAliases(String name);

}

BeanFactory设计定义了ioc的规范。

DefaultListableBeanFactory <— XmlBeanFactory

DefaultListableBeanFactory有容器的完整实现，而XmlBeanFactory是对它的一种扩展，扩展什么看名字就知道了，支持xml数据源的解析。我们看下XmlBeanFactory的代码：

public class XmlBeanFactory extends DefaultListableBeanFactory {
/**
* 换了一个reader
*/
private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);

public XmlBeanFactory(Resource resource) throws BeansException {
this(resource, null);
}

public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
super(parentBeanFactory);
this.reader.loadBeanDefinitions(resource);
}

}

XmlBeanFactory在初始化时调用loadBeanDefinitions方法，使用XmlBeanDefinitionReader去解析元数据，这也是最初的一步。



FileSystemXmlApplicationContext源码：

public class FileSystemXmlApplicationContext extends AbstractXmlApplicationContext {
public FileSystemXmlApplicationContext() {
}
public FileSystemXmlApplicationContext(ApplicationContext parent) {
super(parent);
}
public FileSystemXmlApplicationContext(String configLocation) throws BeansException {
this(new String[] {configLocation}, true, null);
}
public FileSystemXmlApplicationContext(String... configLocations) throws BeansException {
this(configLocations, true, null);
}
public FileSystemXmlApplicationContext(String[] configLocations, ApplicationContext parent) throws BeansException {
this(configLocations, true, parent);
}
public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh) throws BeansException {
this(configLocations, refresh, null);
}

/**
* setConfigLocations 将路径字符串解析到自己存资源配置的configLocations里
* 然后调用refresh()，这也是容器初始化的入口
*
*/
public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {

super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}

/**
* 这是这个FileSystemXml自己的实现部分，getResourceByPath必然是哪一个父类模版方法需要调用的方法
* 而这个方法自己实现提供一个FileSystemResource出来。
* Resource这个就是将元数据转化成容器可以统一可以解析的资源，根据不同的元数据类型，必然需要不同的算法去读取这些数据。
*/
@Override
protected Resource getResourceByPath(String path) {
if (path != null && path.startsWith("/")) {
path = path.substring(1);
}
return new FileSystemResource(path);
}

}

调用AbstractApplicationContext的refresh方法：

标准的模版方法，这里注意继承链路，嵌套的模版方法调用下来。

public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();

// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);

try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);

// Invoke factory processors registered as beans in the context.
// 扩展点1
invokeBeanFactoryPostProcessors(beanFactory);

// Register bean processors that intercept bean creation.
// 扩展点2
registerBeanPostProcessors(beanFactory);

// Initialize message source for this context.
initMessageSource();

// Initialize event multicaster for this context.
initApplicationEventMulticaster();

// Initialize other special beans in specific context subclasses.
onRefresh();

// Check for listener beans and register them.
registerListeners();

// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

// Last step: publish corresponding event.
finishRefresh();
}

catch (BeansException ex) {
// Destroy already created singletons to avoid dangling resources.
destroyBeans();

// Reset 'active' flag.
cancelRefresh(ex);

// Propagate exception to caller.
throw ex;
}
}
}

调用AbstractApplicationContext 的obtainFreshBeanFactory方法：

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
// 这要调用子类的实现=>AbstractRefreshableApplicationContext
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}

AbstractRefreshableApplicationContext的refreshBeanFactory

protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
// 子类实现
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}

AbstractXmlApplicationContext的loadBeanDefinitions

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
// 指定Reader
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
initBeanDefinitionReader(beanDefinitionReader);
//
loadBeanDefinitions(beanDefinitionReader);
}
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}

XmlBeanDefinitionReader继承的基类AbstractBeanDefinitionReader的实现：

public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int counter = 0;
for (String location : locations) {
counter += loadBeanDefinitions(location);
}
return counter;
}
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
return loadBeanDefinitions(location, null);
}
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int counter = 0;
for (Resource resource : resources) {
counter += loadBeanDefinitions(resource);
}
return counter;
}
/*
*最终调用到的实现，这里需要产生Resource，既然用FileSystemXmlApplicationContext
* 那在读取文件产生Resource的过程有它自定义的部分，也就是我们在FileSystemXmlApplicationContext中看到的getResourceByPath会被使用。
*/
public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
}

if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
// 要产生Resource了
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
// 这里是解析Resource的入口
int loadCount = loadBeanDefinitions(resources);
if (actualResources != null) {
for (Resource resource : resources) {
actualResources.add(resource);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
return loadCount;
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"Could not resolve bean definition resource pattern [" + location + "]", ex);
}
}
else {
// Can only load single resources by absolute URL.
Resource resource = resourceLoader.getResource(location);
int loadCount = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
}
}

回到AbstractApplicationContext调用getResources方法，resourcePatternResolver用默认的PathMatchingResourcePatternResolver

public Resource[] getResources(String locationPattern) throws IOException {
return this.resourcePatternResolver.getResources(locationPattern);
}
public AbstractApplicationContext() {
this.resourcePatternResolver = getResourcePatternResolver();
}
//默认PathMatchingResourcePatternResolver
protected ResourcePatternResolver getResourcePatternResolver() {
return new PathMatchingResourcePatternResolver(this);
}

PathMatchingResourcePatternResolver的getResources实现

public Resource[] getResources(String locationPattern) throws IOException {
Assert.notNull(locationPattern, "Location pattern must not be null");
// 一种是classpath开头 一种没有
if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {
// a class path resource (multiple resources for same name possible)
if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {
// a class path resource pattern
return findPathMatchingResources(locationPattern);
}
else {
// all class path resources with the given name
return findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));
}
}
else {
// Only look for a pattern after a prefix here
// (to not get fooled by a pattern symbol in a strange prefix).
int prefixEnd = locationPattern.indexOf(":") + 1;
if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {
// a file pattern
return findPathMatchingResources(locationPattern);
}
else {
// a single resource with the given name
// 使用ResourceLoader来产生Resource
return new Resource[] {getResourceLoader().getResource(locationPattern)};
}
}
}

// 默认使用DefaultResourceLoader来解析路径
public PathMatchingResourcePatternResolver(ClassLoader classLoader) {
this.resourceLoader = new DefaultResourceLoader(classLoader);
}

public ResourceLoader getResourceLoader() {
return this.resourceLoader;
}

DefaultResourceLoader的getResource，而此时返回的Resource是FileSystemResource类型

public Resource getResource(String location) {
Assert.notNull(location, "Location must not be null");
if (location.startsWith("/")) {
// 最终调用子类的getResourceByPath，而这个方法正是FileSystemXmlApplicationContext实现的
return getResourceByPath(location);
}
else if (location.startsWith(CLASSPATH_URL_PREFIX)) {
return new ClassPathResource(location.substring(CLASSPATH_URL_PREFIX.length()), getClassLoader());
}
else {
try {
// Try to parse the location as a URL...
URL url = new URL(location);
return new UrlResource(url);
}
catch (MalformedURLException ex) {
// No URL -> resolve as resource path.
return getResourceByPath(location);
}
}
}

可见FileSystemXmlApplicationContext最终体现在产生的Resource不同实现。



Resource相当于定位到资源的抽象，下一步就是不同Resource解析资源。

回到AbstractBeanDefinitionReader的loadBeanDefinitions。定位后下一步就是解析Resource的入口：

int loadCount = loadBeanDefinitions(resource);

子类XmlBeanDefinitionReader实现：

public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}

Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<EncodedResource>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
// 终于到了java读取文件熟悉的InputStream了，Recoure－>InputStream
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// 继续解析：InputStream -> Document
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
finally {
inputStream.close();
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}

调用到DefaultDocumentLoader实现解析xml

protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
// 继续解析：InputStream -> Document
Document doc = doLoadDocument(inputSource, resource);
// 转化：Document->BeanDefinition
// 显然，从一个Document变成一个个bean的描述（BeanDefinition），就涉及到我们在使用spring时经常用到的bean定义时的各种配置规则，如果查看源码，也许会更好的理解。
return registerBeanDefinitions(doc, resource);
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (SAXParseException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
}
catch (SAXException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"XML document from " + resource + " is invalid", ex);
}
catch (ParserConfigurationException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Parser configuration exception parsing XML from " + resource, ex);
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"IOException parsing XML document from " + resource, ex);
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Unexpected exception parsing XML document from " + resource, ex);
}
}
// 具体documentLoader来实现，DefaultDocumentLoader实现解析xml
protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
getValidationModeForResource(resource), isNamespaceAware());
}

DefaultDocumentLoader使用JAXP方式解析：

public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {

DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
if (logger.isDebugEnabled()) {
logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");
}
DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
return builder.parse(inputSource);
}
protected DocumentBuilder createDocumentBuilder(
DocumentBuilderFactory factory, EntityResolver entityResolver, ErrorHandler errorHandler)
throws ParserConfigurationException {

DocumentBuilder docBuilder = factory.newDocumentBuilder();
if (entityResolver != null) {
docBuilder.setEntityResolver(entityResolver);
}
if (errorHandler != null) {
docBuilder.setErrorHandler(errorHandler);
}
return docBuilder;
}

registerBeanDefinitions方法：

public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
//BeanDefinitionDocumentReader具体实现
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}

BeanDefinitionDocumentReader具体实现：

public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
doRegisterBeanDefinitions(root);
}

protected void doRegisterBeanDefinitions(Element root) {
// Any nested <beans> elements will cause recursion in this method. In
// order to propagate and preserve <beans> default-* attributes correctly,
// keep track of the current (parent) delegate, which may be null. Create
// the new (child) delegate with a reference to the parent for fallback purposes,
// then ultimately reset this.delegate back to its original (parent) reference.
// this behavior emulates a stack of delegates without actually necessitating one.
BeanDefinitionParserDelegate parent = this.delegate;
// 指定好BeanDefinitionParserDelegate
this.delegate = createDelegate(getReaderContext(), root, parent);

if (this.delegate.isDefaultNamespace(root)) {
String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
if (StringUtils.hasText(profileSpec)) {
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
return;
}
}
}
//可扩展入口
preProcessXml(root);
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);

this.delegate = parent;
}

protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
if (delegate.isDefaultNamespace(root)) {
NodeList nl = root.getChildNodes();
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element) {
Element ele = (Element) node;
if (delegate.isDefaultNamespace(ele)) {
// 一次解析每个节点
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
//标签解析
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
//import
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
//alias
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
//bean
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// beans recurse
doRegisterBeanDefinitions(ele);
}
}

如果是beans的标签则进行了递归，查看解析bean标签的代码：

protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
// 终于是解析入口了,Element－>BeanDefinitionHolder
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
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));
}
}
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
return parseBeanDefinitionElement(ele, null);
}

这里的BeanDefinitionHolder包装了BeanDefinition以及bean和alias：

private final BeanDefinition beanDefinition;
private final String beanName;
private final String[] aliases;

BeanDefinitionReaderUtils.registerBeanDefinition：

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
// bean id
String id = ele.getAttribute(ID_ATTRIBUTE);
// bean name
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);

List<String> aliases = new ArrayList<String>();
if (StringUtils.hasLength(nameAttr)) {
String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
aliases.addAll(Arrays.asList(nameArr));
}

String beanName = id;
if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
beanName = aliases.remove(0);
if (logger.isDebugEnabled()) {
logger.debug("No XML 'id' specified - using '" + beanName +
"' as bean name and " + aliases + " as aliases");
}
}

if (containingBean == null) {
checkNameUniqueness(beanName, aliases, ele);
}
// beanDefinition产生 此时已经解析了bean中的其他字段
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
if (!StringUtils.hasText(beanName)) {
try {
if (containingBean != null) {
beanName = BeanDefinitionReaderUtils.generateBeanName(
beanDefinition, this.readerContext.getRegistry(), true);
}
else {
beanName = this.readerContext.generateBeanName(beanDefinition);
// Register an alias for the plain bean class name, if still possible,
// if the generator returned the class name plus a suffix.
// This is expected for Spring 1.2/2.0 backwards compatibility.
String beanClassName = beanDefinition.getBeanClassName();
if (beanClassName != null &&
beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&
!this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
aliases.add(beanClassName);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Neither XML 'id' nor 'name' specified - " +
"using generated bean name [" + beanName + "]");
}
}
catch (Exception ex) {
error(ex.getMessage(), ele);
return null;
}
}
String[] aliasesArray = StringUtils.toStringArray(aliases);
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}

return null;
}

拿到holder后进行注册：

public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {

// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
// 把解析出来到BeanDefinition进行注册
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);
}
}
}

最终DefaultListableBeanFactory中的代码：

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<String>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<String>(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);
}
}

到这里，组装出了一个beanName:beanDefinition的ConcurrentHashMap，后续就是在这个map作为资源的基础上进行依赖注入的。

－－－－－－－－－－－－－－－－－－－－－－

永远爱汀汀