Spring 源码阅读–beans-(1)

/**
*CreateanewXmlBeanFactorywiththegivenresource,
*whichmustbeparsableusingDOM.
*@paramresourceXMLresourcetoloadbeandefinitionsfrom
*@throwsBeansExceptionincaseofloadingorparsingerrors
*/
publicXmlBeanFactory(Resourceresource)throwsBeansException{
this(resource,null);
}

/**
*CreateanewXmlBeanFactorywiththegiveninputstream,
*whichmustbeparsableusingDOM.
*@paramresourceXMLresourcetoloadbeandefinitionsfrom
*@paramparentBeanFactoryparentbeanfactory
*@throwsBeansExceptionincaseofloadingorparsingerrors
*/
publicXmlBeanFactory(Resourceresource,BeanFactoryparentBeanFactory)throwsBeansException{
super(parentBeanFactory);
this.reader.loadBeanDefinitions(resource);
}

/**
*CreateanewAbstractAutowireCapableBeanFactory.
*/
publicAbstractAutowireCapableBeanFactory(){
super();
ignoreDependencyInterface(BeanNameAware.class);
ignoreDependencyInterface(BeanFactoryAware.class);
ignoreDependencyInterface(BeanClassLoaderAware.class);
}

loadBeanDefinitions方法时候使用EncodeResource类进行封装

2.获取输入流。从Resource中获取对应的InputStream并且构造InputSource

3.通过构造的InputSource实例和Resource实例继续调用函数doLoadBeanDefinitions。

源码流程：

publicXmlBeanFactory(Resourceresource)throwsBeansException{
this(resource,null);
}

publicXmlBeanFactory(Resourceresource,BeanFactoryparentBeanFactory)throwsBeansException{
super(parentBeanFactory);
this.reader.loadBeanDefinitions(resource);
}

@Override
publicintloadBeanDefinitions(Resourceresource)throwsBeanDefinitionStoreException{
returnloadBeanDefinitions(newEncodedResource(resource));
}

publicintloadBeanDefinitions(EncodedResourceencodedResource)throwsBeanDefinitionStoreException{
Assert.notNull(encodedResource,"EncodedResourcemustnotbenull");
if(logger.isInfoEnabled()){
logger.info("LoadingXMLbeandefinitionsfrom"+encodedResource.getResource());
}

Set<EncodedResource>currentResources=this.resourcesCurrentlyBeingLoaded.get();
if(currentResources==null){
currentResources=newHashSet<EncodedResource>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if(!currentResources.add(encodedResource)){
thrownewBeanDefinitionStoreException(
"Detectedcyclicloadingof"+encodedResource+"-checkyourimportdefinitions!");
}
try{
InputStreaminputStream=encodedResource.getResource().getInputStream();
try{
InputSourceinputSource=newInputSource(inputStream);
if(encodedResource.getEncoding()!=null){
inputSource.setEncoding(encodedResource.getEncoding());
}
returndoLoadBeanDefinitions(inputSource,encodedResource.getResource());
}
finally{
inputStream.close();
}
}
catch(IOExceptionex){
thrownewBeanDefinitionStoreException(
"IOExceptionparsingXMLdocumentfrom"+encodedResource.getResource(),ex);
}
finally{
currentResources.remove(encodedResource);
if(currentResources.isEmpty()){
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}

protectedintdoLoadBeanDefinitions(InputSourceinputSource,Resourceresource)
throwsBeanDefinitionStoreException{
try{
Documentdoc=doLoadDocument(inputSource,resource);
returnregisterBeanDefinitions(doc,resource);
}
catch(BeanDefinitionStoreExceptionex){
throwex;
}
catch(SAXParseExceptionex){
thrownewXmlBeanDefinitionStoreException(resource.getDescription(),
"Line"+ex.getLineNumber()+"inXMLdocumentfrom"+resource+"isinvalid",ex);
}
catch(SAXExceptionex){
thrownewXmlBeanDefinitionStoreException(resource.getDescription(),
"XMLdocumentfrom"+resource+"isinvalid",ex);
}
catch(ParserConfigurationExceptionex){
thrownewBeanDefinitionStoreException(resource.getDescription(),
"ParserconfigurationexceptionparsingXMLfrom"+resource,ex);
}
catch(IOExceptionex){
thrownewBeanDefinitionStoreException(resource.getDescription(),
"IOExceptionparsingXMLdocumentfrom"+resource,ex);
}
catch(Throwableex){
thrownewBeanDefinitionStoreException(resource.getDescription(),
"UnexpectedexceptionparsingXMLdocumentfrom"+resource,ex);
}
}

loadBeanDefinitions(EncodedResourceencodedResource)，这个方法内部就是真正的数据准备阶段。

然后

doLoadBeanDefinitions方法就是核心算法。

然后它大概做了三件事：

1.获取对xml文件的验证模式

2.加载xml文件，并得到对应的document

3.根据返回的document注册bean信息

三：获取XML的验证模式

xml文件的验证模式保证了xml文件的正确性，比较常用的是两种：DTD和XSD。

DTD和XSD的区别

intvalidationModeToUse=getValidationMode();
if(validationModeToUse!=VALIDATION_AUTO){
returnvalidationModeToUse;
}
intdetectedMode=detectValidationMode(resource);
if(detectedMode!=VALIDATION_AUTO){
returndetectedMode;
}

detectValidationMode中实现，最后来

/**
*DoesthecontentcontainthetheDTDDOCTYPEdeclaration?
*/
privatebooleanhasDoctype(Stringcontent){
return(content.indexOf(DOCTYPE)>-1);
}

@Override
publicDocumentloadDocument(InputSourceinputSource,EntityResolverentityResolver,
ErrorHandlererrorHandler,intvalidationMode,booleannamespaceAware)throwsException{

DocumentBuilderFactoryfactory=createDocumentBuilderFactory(validationMode,namespaceAware);
if(logger.isDebugEnabled()){
logger.debug("UsingJAXPprovider["+factory.getClass().getName()+"]");
}
DocumentBuilderbuilder=createDocumentBuilder(factory,entityResolver,errorHandler);
returnbuilder.parse(inputSource);
}

publicintregisterBeanDefinitions(Documentdoc,Resourceresource)throwsBeanDefinitionStoreException{
BeanDefinitionDocumentReaderdocumentReader=createBeanDefinitionDocumentReader();
documentReader.setEnvironment(this.getEnvironment());
intcountBefore=getRegistry().getBeanDefinitionCount();
documentReader.registerBeanDefinitions(doc,createReaderContext(resource));
returngetRegistry().getBeanDefinitionCount()-countBefore;
}

createBeanDefinitionDocumentReader完成，通过这个方法，然后进入DefaultBeanDefinitionDocumentReader,这个方法的重要目的之一就是提取ROOT以便于再次将root作为参数继续BeanDefinition的注册

@Override
publicvoidregisterBeanDefinitions(Documentdoc,XmlReaderContextreaderContext){
this.readerContext=readerContext;
logger.debug("Loadingbeandefinitions");
Elementroot=doc.getDocumentElement();
doRegisterBeanDefinitions(root);
}

protectedvoiddoRegisterBeanDefinitions(Elementroot){
StringprofileSpec=root.getAttribute(PROFILE_ATTRIBUTE);
if(StringUtils.hasText(profileSpec)){
Assert.state(this.environment!=null,"Environmentmustbesetforevaluatingprofiles");
String[]specifiedProfiles=StringUtils.tokenizeToStringArray(
profileSpec,BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
if(!this.environment.acceptsProfiles(specifiedProfiles)){
return;
}
}

//Anynested<beans>elementswillcauserecursioninthismethod.In
//ordertopropagateandpreserve<beans>default-*attributescorrectly,
//keeptrackofthecurrent(parent)delegate,whichmaybenull.Create
//thenew(child)delegatewithareferencetotheparentforfallbackpurposes,
//thenultimatelyresetthis.delegatebacktoitsoriginal(parent)reference.
//thisbehavioremulatesastackofdelegateswithoutactuallynecessitatingone.
BeanDefinitionParserDelegateparent=this.delegate;
this.delegate=createDelegate(this.readerContext,root,parent);

preProcessXml(root);
parseBeanDefinitions(root,this.delegate);
postProcessXml(root);

this.delegate=parent;
}

protectedvoidparseBeanDefinitions(Elementroot,BeanDefinitionParserDelegatedelegate){
if(delegate.isDefaultNamespace(root)){
NodeListnl=root.getChildNodes();
for(inti=0;i<nl.getLength();i++){
Nodenode=nl.item(i);
if(nodeinstanceofElement){
Elementele=(Element)node;
if(delegate.isDefaultNamespace(ele)){
parseDefaultElement(ele,delegate);
}
else{
delegate.parseCustomElement(ele);
}
}
}
}
else{
delegate.parseCustomElement(root);
}
}