IOC容器初始化是由refresh()方法来启动的，这个方法标志着IOC容器的正式启动。Spring将IOC容器启动的过程分开，并使用不同的模块来完成，如使用ResourceLoader，BeanDefinition等模块， IOC容器的启动主要包括三个过程：
- Resource定位过程：
Resource定位指beanDefinition的资源定位，由ResourceLoader通过统一的Resource接口来完成，这个Resource对各种形式的BeanDefinition的使用都提供了统一的接口。这个过程类似于容器寻找数据的过程。
- BeanDefinition的载入：
BeanDefinition载入过程指的是把用户定义好的Bean表示为容器内部的数据结构，这个容器的数据结构其实就是BeanDefinition。实际上BeanDefinition就是POJO对象在容器的抽象，通过BeanDefinition来定义的数据结构，像是世间万物在java中的抽象，java的对象又在容器中的抽象就是BeanDefinition。
- 向容器注册BeanDefinition：
这个注册过程是通过调用BeanDefinitionRegistry接口来完成的，就是把载入过程中解析得到的BeanDefinition向IOC容器进行注册。通过下面的源码可以得到，注册过程就是在IOC容器将BeanDefinition注入到一个HashMap中，IOC容器就是通过这个HashMap来持有BeanDefinition数据的。
自己手写一个IOC容器的初始化
//创建IOC配置文件的抽象资源，这个抽象资源包含了BeanDefinition的定义信息
ClassPathResource resource = new ClassPathResource("bean.xm");
//创建一个bean工厂
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
//创建一个读取器，这里使用XmlBeanDefinitionReader来载入XML文件形式的Bean工厂
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
//XMLBeanFactory具体使用reader读入配置信息
reader.loadBeanDefinitions(resource);
1、BeanDefinition的Resource定位
以上面编程式的使用DefaultListablebeanFactory时，首先需要定义一个Resource来定位容器BeanDefinition。DefaultListableBeanFactory不能够直接使用Resource，需要一个BeanDefinition来对这些信息进行处理，ApplicationContext中，Spring已经提供了一系列不同的Resource的读取器的实现。
常用的Resource资源类型如下：
- FileSystemResource：以文件的绝对路径方式进行访问资源，效果类似于Java中的File;
- ClassPathResourcee：以类路径的方式访问资源，效果类似于this.getClass().getResource("/").getPath();
- ServletContextResource：web应用根目录的方式访问资源，效果类似于request.getServletContext().getRealPath("");
- UrlResource：访问网络资源的实现类。例如file: http: ftp:等前缀的资源对象;
- ByteArrayResource: 访问字节数组资源的实现类
下面具体说一下，以FileSystemXmlApplicationContext为例的BeanDefinition的定位过程。
1、FileSystemXmlApplicationContext的类关系
直接就是一个图：
从上面的继承关系来看，FileSystemXmlApplicationContext继承于AbstractApplicationContext，AbstractApplicationContext的基类是DefaultResourceLoader来继承了ResourceLoader的能力。
首先看一下FileSystemXmlApplicationContext的具体实现
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);
}
public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
@Override
protected Resource getResourceByPath(String path) {
if (path != null && path.startsWith("/")) {
path = path.substring(1);
}
return new FileSystemResource(path);
}
在构造方法的中调用了refresh方法，这个方法标志着启动IOC容器的初始化，我们点进去，进入到了FileSystemXmlApplicationContext的基类AbstractApplicationContext中。
@Override
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.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
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) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
这个Refresh方法其实是与Bean的生命周期有关，这里我还没有具体看Bean声明周期这一块，等我看完再做具体解释。这里重点看obtainFreshbeanFactory()这个方法，这个方法是IOC容器初始化的入口。
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
obtainFreshBeanFactory方法中调用了refreshBeanFactory方法，这个方法是一个抽象的，具体的实现是根据它的子类的具体情况来定的，由于我们现在看的是FileSystemXmlApplicationContext的过程，所以我们进入AbstractFreshableApplicationContext类中的refreshBeanFactory方法中
@Override
protected final void refreshBeanFactory() throws BeansException {
//这里判断了是否存在BeanFactory，如果存在就销毁并关闭BeanFactory
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
//这里去创建新的Beanfactory,创建的是DefaultListableBeanFactory
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
//载入Bean
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
继续点入载入方法loadBeanDefinition中，这个方法有很多的重载。
点入的loadBeanDefinition方法也是一个抽象方法，需要去实现类中查看，我们还是选择与FileSystemXmlApplicationContext相关的AbstractXmlApplicationContext类中
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
//创建一个配置读写器
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
//设置BeanDefinition的相关属性
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
//传入读写器
initBeanDefinitionReader(beanDefinitionReader);
//加载获取BeanDefinition定位
loadBeanDefinitions(beanDefinitionReader);
}
继续点入loadBeanDefinition方法
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
//初始化不会走一条路，因为还没有Resource对象
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
//以String文件的方式获取
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}
点入第二个loadBeanDefinition方法进入。
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int counter = 0;
String[] var3 = locations;
int var4 = locations.length;
//循环加载配置文件
for(int var5 = 0; var5 < var4; ++var5) {
String location = var3[var5];
counter += this.loadBeanDefinitions(location);
}
loadBeanDefinition方法继续点入，查看加载过程
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
return this.loadBeanDefinitions(location, (Set)null);
}
public int loadBeanDefinitions(String location, Set actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = this.getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException("Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
} else {
int loadCount;
if (!(resourceLoader instanceof ResourcePatternResolver)) {
Resource resource = resourceLoader.getResource(location);
loadCount = this.loadBeanDefinitions((Resource)resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (this.logger.isDebugEnabled()) {
this.logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
} else {
try {
//获取Resource具体的定位
Resource[] resources = ((ResourcePatternResolver)resourceLoader).getResources(location);
loadCount = this.loadBeanDefinitions(resources);
if (actualResources != null) {
Resource[] var6 = resources;
int var7 = resources.length;
for(int var8 = 0; var8 < var7; ++var8) {
Resource resource = var6[var8];
actualResources.add(resource);
}
}
if (this.logger.isDebugEnabled()) {
this.logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
return loadCount;
} catch (IOException var10) {
throw new BeanDefinitionStoreException("Could not resolve bean definition resource pattern [" + location + "]", var10);
}
}
}
}
直接看一下DefaultResourceLoader的getResource方法
public Resource getResource(String location) {
Assert.notNull(location, "Location must not be null");
Iterator var2 = this.protocolResolvers.iterator();
Resource resource;
do {
if (!var2.hasNext()) {
if (location.startsWith("/")) {
return this.getResourceByPath(location);
}
if (location.startsWith("classpath:")) {
return new ClassPathResource(location.substring("classpath:".length()), this.getClassLoader());
}
try {
URL url = new URL(location);
return new UrlResource(url);
} catch (MalformedURLException var5) {
return this.getResourceByPath(location);
}
}
ProtocolResolver protocolResolver = (ProtocolResolver)var2.next();
resource = protocolResolver.resolve(location, this);
} while(resource == null);
return resource;
}
如果Resource不是Url也不是classpath资源，那么就调用FileSystemXmlApplicationContext的getResourceByPath方法返回一个FileSystemResource，定位到Resource。接下来就是载入BeanDefinition.
2、BeanDefinition的载入和解析我们接着上面的，继续进入loadBeanDefinitions（）方法，查看载入过程
查看BeanDefinitionReader的实现类XmlBeanDefinitionReader的loadBeanDefinitions方法
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
return this.loadBeanDefinitions(new EncodedResource(resource));
}
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (this.logger.isInfoEnabled()) {
this.logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
Set currentResources = (Set)this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!((Set)currentResources).add(encodedResource)) {
throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!");
} else {
int var5;
try {
//通过Resource对象将XMl输入文件流中
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//具体读取流的方法
var5 = this.doLoadBeanDefinitions(inputSource, encodedResource.getResource());
} finally {
inputStream.close();
}
} catch (IOException var15) {
throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), var15);
} finally {
((Set)currentResources).remove(encodedResource);
if (((Set)currentResources).isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
return var5;
}
}
我们继续点入到doLoadBeanDefinitions方法中查看
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException {
try {
document doc = this.doLoaddocument(inputSource, resource);
return this.registerBeanDefinitions(doc, resource);
} catch (BeanDefinitionStoreException var4) {
throw var4;
} catch (SAXParseException var5) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(), "Line " + var5.getLineNumber() + " in XML document from " + resource + " is invalid", var5);
} catch (SAXException var6) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(), "XML document from " + resource + " is invalid", var6);
} catch (ParserConfigurationException var7) {
throw new BeanDefinitionStoreException(resource.getDescription(), "Parser configuration exception parsing XML from " + resource, var7);
} catch (IOException var8) {
throw new BeanDefinitionStoreException(resource.getDescription(), "IOException parsing XML document from " + resource, var8);
} catch (Throwable var9) {
throw new BeanDefinitionStoreException(resource.getDescription(), "Unexpected exception parsing XML document from " + resource, var9);
}
}
这个方法就是将Resource文件的输入流解析为Xml文件的document对象，然后经过registerBeanDefinition方法将document对象解析成BeanDefinition（容器内部的数据结构）
public int registerBeanDefinitions(document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitiondocumentReader documentReader = this.createBeanDefinitiondocumentReader();
int countBefore = this.getRegistry().getBeanDefinitionCount();
documentReader.registerBeanDefinitions(doc, this.createReaderContext(resource));
return this.getRegistry().getBeanDefinitionCount() - countBefore;
}
继续点入registerBeanDefinitions（）方法中
public void registerBeanDefinitions(document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
this.logger.debug("Loading bean definitions");
Element root = doc.getdocumentElement();
this.doRegisterBeanDefinitions(root);
}
这个方法将Xml的元素取出来，继续进入doRegisterBeanDefinitions（）方法
protected void doRegisterBeanDefinitions(Element root) {
BeanDefinitionParserDelegate parent = this.delegate;
this.delegate = this.createDelegate(this.getReaderContext(), root, parent);
if (this.delegate.isDefaultNamespace(root)) {
String profileSpec = root.getAttribute("profile");
if (StringUtils.hasText(profileSpec)) {
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, ",; ");
if (!this.getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
if (this.logger.isInfoEnabled()) {
this.logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec + "] not matching: " + this.getReaderContext().getResource());
}
return;
}
}
}
this.preProcessXml(root);
this.parseBeanDefinitions(root, this.delegate);
this.postProcessXml(root);
this.delegate = parent;
}
在这个方法中，我们重点看“一类三法”，也就是BeanDefinitionParserDelegate类和preProcessXml、parseBeanDefinitions、postProcessXml三个方法。其中BeanDefinitionParserDelegate类非常非常重要（需要了解代理技术，如JDK动态代理、cglib动态代理等）。Spirng BeanDefinition的解析就是在这个代理类下完成的，此类包含了各种对符合Spring Bean语义规则的处理，比如
前面提到document对象不能通过XmlBeanDefinitionReader，真正去解析document文档树的是 BeanDefinitionParserDelegate完成的，这个解析过程是与Spring对BeanDefinition的配置规则紧密相关的，parseBeanDefinitions(root, delegate)方法如下：
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)) {
//默认标签
this.parseDefaultElement(ele, delegate);
} else {
delegate.parseCustomElement(ele);
}
}
}
} else {
delegate.parseCustomElement(root);
}
}
继续进入parseDefaultElement方法
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, "import")) {
this.importBeanDefinitionResource(ele);
} else if (delegate.nodeNameEquals(ele, "alias")) {
this.processAliasRegistration(ele);
} else if (delegate.nodeNameEquals(ele, "bean")) {
this.processBeanDefinition(ele, delegate);
} else if (delegate.nodeNameEquals(ele, "beans")) {
this.doRegisterBeanDefinitions(ele);
}
}
是bean标签，进入processBeanDefinition方法，这里有一点就是所有的BeanDefinition都是存放在
BeanDefinitionHolder 中。
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, this.getReaderContext().getRegistry());
} catch (BeanDefinitionStoreException var5) {
this.getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, var5);
}
this.getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
而且具体的从document解析成BeanDefinition的过程是由GeanDefinitionParserDelegate来完成的。我们继续点入parseBeanDefinitionElement这个方法
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
return parseBeanDefinitionElement(ele, null);
}
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
String id = ele.getAttribute(ID_ATTRIBUTE);
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
List 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);
}
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;
}
这个方法将Bean标签的内容放入到BeanDefinition中，并且将其他的信息也放入到BeanDefinitionHolder中，
上面的解析过程可以看做根据xml文件对
接着我们看一下Bean的具体解析，这就是将Bean具体的解析。
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
try {
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DEscriptION_ELEMENT));
parsemetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
parseConstructorArgElements(ele, bd);
parsePropertyElements(ele, bd);
parseQualifierElements(ele, bd);
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
return bd;
}
catch (ClassNotFoundException ex) {
error("Bean class [" + className + "] not found", ele, ex);
}
catch (NoClassDefFoundError err) {
error("Class that bean class [" + className + "] depends on not found", ele, err);
}
catch (Throwable ex) {
error("Unexpected failure during bean definition parsing", ele, ex);
}
finally {
this.parseState.pop();
}
return null;
}
看到这里，我们就将BeanDefinition的载入过程的源码看完了。
3、BeanDefinition在IOC容器的注册接着我们来看BeanDefinition的注册过程
我们回到DefaultBeanDefinitiondocumentReader类中的processBeanDefinition（）方法，这里先将BeanDefinition载入，然后得到BeanDefinitionHodler来进行注册。
点击进入registerBeanDefinition方法，这里是注册的入口。
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);
}
}
}
这个方法是将BeanDefinitionHodler分解开，得到BeanName和BeanDefinition，然后继续调用
注册接口的接口，然后去具体的容器类将key--BeanName和value--BeanDefinition放入到容器的beanDefinitionMap的一个HashMap中，这个方法会判断Bean是否存在。
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 updatedDefinitions = new ArrayList(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set 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);
}
}
以上就是Ioc容器的初始化过程，但是这个只是Bean生命周期的第一步，Bean的实例化，接着我会继续写依赖注入，调用Bean的初始化方法等关于Bean的知识文章。欢迎大家关注我，继续关注我文章。
