Spring源碼之XMLBeanFactory
本文是針對Srping的XMLBeanFactory來進行解析xml並將解析後的信息使用GenericBeanDefinition做爲載體進行註冊,xmlBeanFactory已經在Spring 3.1中被標記爲不建議使用，可是咱們分析源碼不影響，由於源碼並未改變，並ApplicationContext依舊使用XmlBeanDefinitionReader和DefaultListableBeanFactory進行xml的解析和註冊工做，本篇博客是跟源碼一步步看spring怎麼實現bean的註冊，源碼爲spring5.X,源碼已經在每一行上加了註釋，方便讀者學習。node
GitHub:github.com/lantaoGitHu…git
- 首先咱們從XMLBeanFactory入手,直接上代碼：
package org.springframework.lantao;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
public class XmlBeanFactoryTest {
public static void main(String[] args) {
// 資源加載
ClassPathResource classPathResource = new ClassPathResource("spring-bean.xml");
// XmlBeanFactory 加載資源並解析註冊bean
BeanFactory beanFactory = new XmlBeanFactory(classPathResource);
// BeanFactory.getBean();
UserBean userBean = (UserBean) beanFactory.getBean("userBean");
System.out.println(userBean.getName());
}
}
複製代碼
- XmlBeanFactory解析Xml是使用了XmlBeanDefinitionReader.loadBeanDefinition()方法,源碼以下：
@Deprecated
@SuppressWarnings({"serial", "all"})
public class XmlBeanFactory extends DefaultListableBeanFactory {
private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);
/**
* Create a new XmlBeanFactory with the given resource,
* which must be parsable using DOM.
* @param resource the XML resource to load bean definitions from
* @throws BeansException in case of loading or parsing errors
*/
public XmlBeanFactory(Resource resource) throws BeansException {
//調用構造方法 79行
this(resource, null);
}
/**
* Create a new XmlBeanFactory with the given input stream,
* which must be parsable using DOM.
* @param resource the XML resource to load bean definitions from
* @param parentBeanFactory parent bean factory
* @throws BeansException in case of loading or parsing errors
*/
public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
//ignoreDependencyInterface 忽略自動裝配
//主要功能就是當有忽略的接口類，自動裝配會忽略這部分類的初始化裝配，由於某種狀況下，此時的接口實現類不能初始化，列如BeanNameAware,要想裝配這個接口的實現對象，能夠實現這個接口。
super(parentBeanFactory);
//這段代碼是真正的資源加載
this.reader.loadBeanDefinitions(resource);
}
}複製代碼
- 咱們直接看loadBeanDefinition方法，源碼：
/**
* Load bean definitions from the specified XML file.
* @param resource the resource descriptor for the XML file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
*/
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
// 對EncodedResource進行封裝，設置String encoding, Charset charset
return loadBeanDefinitions(new EncodedResource(resource));
}
/**
* Load bean definitions from the specified XML file.
* @param encodedResource the resource descriptor for the XML file,
* allowing to specify an encoding to use for parsing the file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
*/
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
//encodedResource 不能夠爲空
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isTraceEnabled()) {
logger.trace("Loading XML bean definitions from " + encodedResource);
}
// 經過屬性來記錄已經加載的資源
Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
// 從encodedResource已經封裝的Resource獲取InputStream
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
//InputSource 並非spring的，而是 org.xml.sax
InputSource inputSource = new InputSource(inputStream);
//若是encodedResource 中的 Encoding 不是 null 則同步設置 InputSource的 Encoding
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//加載bean的Definitions 將xml中的信息加載到Definition中，而且在內存中註冊的也是key+definitions
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();
}
}
}複製代碼
上述源碼可能看着比較長,但實際上這裏並非真正解析的地方，在這裏作了以下：github
1:從encodedResource已經封裝的Resource獲取InputStream；spring
2:若是encodedResource 中的 Encoding 不是 null 則同步設置 InputSource的 Encoding；express
3:將解析動做委託給doLoadBeanDefinitions實現；緩存
- 接下來咱們繼續看doLoadBeanDefinitions方法內容：
/**
* Actually load bean definitions from the specified XML file.
* @param inputSource the SAX InputSource to read from
* @param resource the resource descriptor for the XML file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
* @see #doLoadDocument
* @see #registerBeanDefinitions
*/
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
//加載 Document
Document doc = doLoadDocument(inputSource, resource);
//註冊 bean
int count = registerBeanDefinitions(doc, resource);
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + count + " bean definitions from " + resource);
}
return count;
}
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);
}
}複製代碼
當咱們看着這個方法的時候，依舊不是真正的解析或註冊的方法，在這裏只是作了Document的加載，並將後續工做委託給了registerBeanDefinitions,registerBeanDefinitions方法的返回時註冊Bean的個數；安全
- 咱們繼續看registerBeanDefinitions的源碼：
/**
* Register the bean definitions contained in the given DOM document.
* Called by {@code loadBeanDefinitions}.
* <p>Creates a new instance of the parser class and invokes
* {@code registerBeanDefinitions} on it.
* @param doc the DOM document
* @param resource the resource descriptor (for context information)
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of parsing errors
* @see #loadBeanDefinitions
* @see #setDocumentReaderClass
* @see BeanDefinitionDocumentReader#registerBeanDefinitions
*/
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
//實例化 BeanDefinitionDocumentReader
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
//獲取以前的beanDefinition加載個數
int countBefore = getRegistry().getBeanDefinitionCount();
//加載xml及註冊bean
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
//記錄本次加載個數
return getRegistry().getBeanDefinitionCount() - countBefore;
}複製代碼
在registerBeanDefinitions方法具體實現：bash
1：經過BeanUtils.instantiateClass(this.documentReaderClass)的方法實例化BeanDefinitionDocumentReader；ide
2：經過DefaultListAbleBeanFactory中的beanDefinitionMap.size()獲取以前註冊bean的個數，（beanDefinitionMap是存儲最終的xml解析後信息的載體，xml解析後信息是由GenericBeanDefinition進行存儲，beanDefinitionMap的存儲格式是key:String value:GenericBeanDefinition）函數
3:將解析xml和註冊的工做委託給BeanDefinitionDocumentReader的registerBeanDefinitions方法；
4：記錄本次加載個數並返回；
- 繼續看BeanDefinitionDocumentReader的registerBeanDefinitions方法：
/**
* This implementation parses bean definitions according to the "spring-beans" XSD
* (or DTD, historically).
* <p>Opens a DOM Document; then initializes the default settings
* specified at the {@code <beans/>} level; then parses the contained bean definitions.
*/
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
//實例化 ReaderContext
this.readerContext = readerContext;
//註冊
doRegisterBeanDefinitions(doc.getDocumentElement());
}複製代碼
- registerBeanDefinitions並無作什麼，咱們繼續看doRegisterBeanDefinitions方法：
/**
* Register each bean definition within the given root {@code <beans/>} element.
*/
@SuppressWarnings("deprecation") // for Environment.acceptsProfiles(String...)
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;
this.delegate = createDelegate(getReaderContext(), root, parent);
//驗證xml namespace, BeanDefinitionParserDelegate.BEANS_NAMESPACE_URI
if (this.delegate.isDefaultNamespace(root)) {
//獲取Attribute
String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
if (StringUtils.hasText(profileSpec)) {
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
// We cannot use Profiles.of(...) since profile expressions are not supported
// in XML config. See SPR-12458 for details.
if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
if (logger.isDebugEnabled()) {
logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec +
"] not matching: " + getReaderContext().getResource());
}
return;
}
}
}
//解析前處理， 內容null 留個子類實現
preProcessXml(root);
//解析
parseBeanDefinitions(root, this.delegate);
//解析後處理， 內容null 留個子類實現
postProcessXml(root);
this.delegate = parent;
}複製代碼
在doRegisterBeanDefinitions煩那個發中驗證xml的namespace,最重要的方法是parseBeanDefinitions，parseBeanDefinitions方法進行了解析操做；
- parseBeanDefinitions方法的源碼：
/**
* Parse the elements at the root level in the document:
* "import", "alias", "bean".
* @param root the DOM root element of the document
*/
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
//驗證xml namespace, BeanDefinitionParserDelegate.BEANS_NAMESPACE_URI
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)) {
//對默認標籤處理
parseDefaultElement(ele, delegate);
}
else {
//對自定義標籤處理
delegate.parseCustomElement(ele);
}
}
}
}
else {
//對自定義標籤處理
delegate.parseCustomElement(root);
}
}複製代碼
parseBeanDefinitions方法中已經開始對標籤進行解析，區分默認標籤和自定義標籤，咱們本次只對默認標籤的源碼進行解析，自定義標籤自行DeBug，
- parseDefaultElement方法的源碼：
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
//解析import標籤
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
//解析alias標籤並註冊
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
//解析bean標籤並註冊
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
//解析beans標籤
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}複製代碼
到這裏咱們能夠看到，spring對import/bean/alias/beans的解析過程，對於beans的解析沒法就是解析beans中的bean標籤，spring直接又從新調用了doRegisterBeanDefinitions方法，咱們接下來進行對bean標籤的解析；
- processBeanDefinition方法：
/**
* Process the given bean element, parsing the bean definition
* and registering it with the registry.
*/
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//委託BeanDefinitionParserDelegate的parseBeanDefinitionElement方法進行元素解析並返回
//BeanDefinitionHolder實例，BeanDefinitionHolder已經包含了配置文件中的各類屬性
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
//當BeanDefinitionHolder返回不null的狀況，弱存在默認標籤下的子標籤再有自定義的屬性，還須要再次解析
if (bdHolder != null) {
//解析默認標籤中的自定義標籤
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
// 進行實例註冊註冊操做是BeanDefinitionReaderUtisl.registerBeanDefinition進行處理
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));
}
}複製代碼
在processBeanDefinition方法中，spring作了兩件事情：
1：委託BeanDefinitionParserDelegate的parseBeanDefinitionElement方法進行元素解析並返回BeanDefinitionHolder實例，BeanDefinitionHolder已經包含了配置文件中的各類屬性
2：經過上得到的BeanDefinitionHolder進行bean的註冊操做，通BeanDefinitionReaderUtils.registerBeanDefinition方法；
- 經過delegate.parseBeanDefinitionElement方法進行xml解析：
/**
* Parses the supplied {@code <bean>} element. May return {@code null}
* if there were errors during parse. Errors are reported to the
* {@link org.springframework.beans.factory.parsing.ProblemReporter}.
*/
@Nullable
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
//解析id屬性
String id = ele.getAttribute(ID_ATTRIBUTE);
//解析name屬性
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
//分割name屬性
List<String> 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.isTraceEnabled()) {
logger.trace("No XML 'id' specified - using '" + beanName +
"' as bean name and " + aliases + " as aliases");
}
}
if (containingBean == null) {
checkNameUniqueness(beanName, aliases, ele);
}
//將信息封裝到 beanDefinition中
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
if (!StringUtils.hasText(beanName)) {
try {
//beanname不存在則使用默認規則建立
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.isTraceEnabled()) {
logger.trace("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;
}複製代碼
在parseBeanDefinitionElement方法中作了三件事：
1：解析id/name；
2：檢查name的惟一性；
3：將信息封裝到 beanDefinition中，接下來直接看parseBeanDefinitionElement方法；
- parseBeanDefinitionElement源碼：
/**
* Parse the bean definition itself, without regard to name or aliases. May return
* {@code null} if problems occurred during the parsing of the bean definition.
*/
@Nullable
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, @Nullable BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
//解析classname屬性
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
String parent = null;
//解析parent屬性
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
try {
//建立用於承載屬性的AbstractBeanDefinition類型的
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
//解析bean的各類屬性
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
//提取description
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
//解析meta （元數據）
parseMetaElements(ele, bd);
//解析Lookup-method 書中53頁有使用方法
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
//解析replaced-method 書中55頁有使用方法
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
//構造函數 參數
//解析constructor-arg 書中replaced-method後邊
parseConstructorArgElements(ele, bd);
//解析Property 書中replaced-method後邊
parsePropertyElements(ele, bd);
//解析Qualifier 書中Property後邊
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;
}複製代碼
經過上述代碼咱們能夠看到這裏首先是實例化了一個AbstractBeanDefinition來承載各類xml屬性，接下來經過parseBeanDefinitionAttributes方法解析了xml中的各類你屬性值，而後在解析lookUp-method(方法注入)，replaced-method(替換方法或方法返回值)，構造函數參數constructor-arg，property屬性，Qualifier屬性等；上述方法的源碼就不一一展現了，無非都是經過Element進行解析；
- 接下來看真正註冊的代碼 BeanDefinitionReaderUtils.registerBeanDefinition
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
//beanName不可爲空
Assert.hasText(beanName, "Bean name must not be empty");
//beanDefinition不可爲空
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
if (beanDefinition instanceof AbstractBeanDefinition) {
try {
//校驗 MethodOverrides，MethodOverrides在解析並組裝beanDefinition時有提到
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
//beanDefinitionMap 存儲實例的全局Map 使用ConcurrentHashMap 線程安全
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
//若是已經註冊 處理內容
if (existingDefinition != null) {
//是否覆蓋
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isInfoEnabled()) {
logger.info("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
//判斷是否已經至少建立過一次 使用AbstractBeanFactory.alreadyCreated來判斷
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<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// 仍處於啓動註冊階段
// 註冊 beanDefinitionMap 新實例 beanName + beanDefinition
this.beanDefinitionMap.put(beanName, beanDefinition);
// 增長beanDefinitionNames
this.beanDefinitionNames.add(beanName);
// 清除緩存
this.manualSingletonNames.remove(beanName);
}
// 清除緩存
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}複製代碼
上述代碼中首先驗證了beanName和BeannDefinition不可爲空,而後繼續校驗了MethodOverridesMethodOverrides在解析並組裝beanDefinition時lookup-method和recpse-method的源碼中有提到，繼續判斷beanDefinitionMap是否存在該bean，若是bean已經存在，經過allowBeanDefinitionOverriding屬性判斷是否可覆蓋，反之則拋出異常；若是不存在則須要判斷本次是不是第一次註冊bean，若是是則初始化beanDefinitionMap後進行put操做，反之直接put beanDefinitionMap完成註冊；
至此咱們已經看完了整個XmlBeanFactory的xml解析和註冊的源碼部分，相信看本篇文章沒法真正理解，還須要讀者下載源碼使用debug運行，再結合本篇文章的註釋，相信會很容易理解，碼字不易，轉發請註明出處：blog.csdn.net/qq_30257149… 或 https://juejin.im/editor/drafts/5c8c80b7f265da2dc23231da
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相關文章
- 1. 【spring源碼】XmlBeanFactory的加載過程
- 2. Spring5.x之XmlBeanFactory源碼解析(一)
- 3. Spring源碼深度解析（XmlBeanFactory源碼解析上）
- 4. spring源碼之容器加載XmlBeanFactory實現過程
- 5. Spring源碼解析02：Spring IOC容器之XmlBeanFactory啓動流程分析和源碼解析
- 6. Spring源碼解析二 (IOC容器初始化方式一:XmlBeanFactory)
- 7. Spring源碼深度解析（四）容器的基礎XmlBeanFactory
- 8. Spring源碼深度解析總結（1）——XmlBeanFactory的結構組成
- 9. Spring源碼 學習---XmlBeanFactory--- 容器的基本實現
- 10. Spring容器基礎XmlBeanFactory(二)