spring-bean解析过程
bean解析源码分析
我是将源码下载到本地,然后搭建起来。
以xml的加载为例进行分析
编写一个测试用例
public class XmlBeanFactoryTest {
public static void main(String[] args) {
/*ClassPathXmlApplicationContext context = new
ClassPathXmlApplicationContext("customtag.xml");*/
XmlBeanFactory xmlBeanFactory = new XmlBeanFactory(new ClassPathResource("spring-bean.xml"));
TestDao testDao = xmlBeanFactory.getBean("testDao", TestDao.class);
testDao.test();
}
}
从构造方法来看,XmlBeanFactory 首先通过ClassPathResource类来加载路径
public ClassPathResource(String path, @Nullable ClassLoader classLoader) {
Assert.notNull(path, "Path must not be null");
String pathToUse = StringUtils.cleanPath(path);
if (pathToUse.startsWith("/")) {
pathToUse = pathToUse.substring(1);
}
this.path = pathToUse;
this.classLoader = (classLoader != null ? classLoader : ClassUtils.getDefaultClassLoader());
}
加载路径完成,通过XmlBeanDefinitionReader类的loadBeanDefinitions方法
public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
super(parentBeanFactory);
//通过loadBeanDefinitions来加载资源
this.reader.loadBeanDefinitions(resource);
}
进入loadBeanDefinitions
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
//将文件转换成编码文件
return loadBeanDefinitions(new EncodedResource(resource));
}
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isTraceEnabled()) {
logger.trace("Loading XML bean definitions from " + encodedResource);
}
//通过属性记录加载的资源
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 {
//从encodedResource中获取已经封装Resource对象,并且再次从Resource对象中获取InputStream流
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
//InputSource 这个类并不米自于 Spring ,它的全路径是org.xml.sax.InputSource
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//进入核心
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();
}
}
}
进入doLoadBeanDefinitions方法,里面主要是包含doLoadDocument()和registerBeanDefinitions()两个方法
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
//加载xml文件,对应到Document
Document doc = doLoadDocument(inputSource, resource);
//根据返回的Document注册bean信息
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);
}
}
分析doLoadDocument()方法
DocumentLoader是一个接口,通过子类DefaultDocumentLoader来进行加载
protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
getValidationModeForResource(resource), isNamespaceAware());
}
/*
*EntityResolver 通过这个类来找到对应本地的DTD或者XSD文件,不需要通过网络去进行解析
*/
public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {
//创建一个DocumentBuilderFactory工厂
DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
if (logger.isTraceEnabled()) {
logger.trace("Using JAXP provider [" + factory.getClass().getName() + "]");
}
//
DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
//放回一个Document对象
return builder.parse(inputSource);
}
registerBeanDefinitions方法
registerBeanDefinitions方法主要就是通过对应的Document进行bean的解析和注册
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
//使用defaultBeanDefinitionDocumentReader实例化BeanDefinitionDocumentReader
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
//获取注册前bean实例的数量
int countBefore = getRegistry().getBeanDefinitionCount();
//加载和注册bean实例
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
//返回本次加载的BeanDefinition数量
return getRegistry().getBeanDefinitionCount() - countBefore;
}
registerBeanDefinitions方法
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
doRegisterBeanDefinitions(doc.getDocumentElement());
}
protected void doRegisterBeanDefinitions(Element root) {
//专门处理解析
BeanDefinitionParserDelegate parent = this.delegate;
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);
// 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;
}
}
}
//解析处理前,留给子类实现
preProcessXml(root);
//将xml解析成BeanDefinition
parseBeanDefinitions(root, this.delegate);
//解析处理后,留给子类实现
postProcessXml(root);
this.delegate = parent;
}
parseBeanDefinitions方法
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;
//默认类型,使用默认解析
if (delegate.isDefaultNamespace(ele)) {
parseDefaultElement(ele, delegate);
}
//自定义类型,使用自定义解析
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
parseDefaultElement方法
如果是默认解析类型,使用parseDefaultElement方法进行解析,对应着四种标签类型
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
//import标签解析和注册
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
//alias别名解析和注册
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
//bean解析和注册
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
//beans解析和注册
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
默认解析(以bean标签为例)
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//解析xml配置信息,将其加载到BeanDefinitionHolder
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
//对bean中自定义的属性进行装饰
/*
* <bean id="testDao" class="com.jack.TestDao">
<mybean:user username=” aaa ”>
* </bean>
* */
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
//注册解析的BeanDefinition,实现在DefaultListableBeanFactory中
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
//通知监听器解析和注册完成
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
解析xml将返回BeanDefinitionHolder
//解析xml配置信息,将其加载到BeanDefinitionHolder
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
String id = ele.getAttribute(ID_ATTRIBUTE);
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
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);
}
//解析xml
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.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;
}
//解析元素
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, @Nullable BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
try {
//创建一个BeanDefinition
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
//解析BeanDefinition的属性
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
//添加描述
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
//解析meta子元素
parseMetaElements(ele, bd);
//解析lookup-method子元素
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
//解析repalced-method子元素
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
//解析Constructor-Arg子元素 初始化
parseConstructorArgElements(ele, bd);
//解析子元素property 对属性初始化
parsePropertyElements(ele, bd);
//解析子元素qualifier
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;
}
对bean中自定义的属性进行装饰
public BeanDefinitionHolder decorateBeanDefinitionIfRequired(
Element ele, BeanDefinitionHolder originalDef, @Nullable BeanDefinition containingBd) {
BeanDefinitionHolder finalDefinition = originalDef;
// Decorate based on custom attributes first.
NamedNodeMap attributes = ele.getAttributes();
for (int i = 0; i < attributes.getLength(); i++) {
Node node = attributes.item(i);
finalDefinition = decorateIfRequired(node, finalDefinition, containingBd);
}
// Decorate based on custom nested elements.
NodeList children = ele.getChildNodes();
for (int i = 0; i < children.getLength(); i++) {
Node node = children.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {
finalDefinition = decorateIfRequired(node, finalDefinition, containingBd);
}
}
return finalDefinition;
}
注册bean
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
//通过beanName作为唯一来进行注册
String beanName = definitionHolder.getBeanName();
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
//通过别名来进行注册
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
注册bean是在DefaultListableBeanFactory
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 existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
//如果bean已经注册了,不允许被覆盖,那么抛出异常
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 {
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;
removeManualSingletonName(beanName);
}
}
else {
// Still in startup registration phase
//注册bean
this.beanDefinitionMap.put(beanName, beanDefinition);
//记录bean
this.beanDefinitionNames.add(beanName);
//更新单例工厂集合
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
//重置所有bean对应的缓存
resetBeanDefinition(beanName);
}
else if (isConfigurationFrozen()) {
clearByTypeCache();
}
}
通知监听器解析和注册完成
//这个是一个空实现,可以由开发人员来进行实现
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
自定义解析
public BeanDefinition parseCustomElement(Element ele, @Nullable BeanDefinition containingBd) {
String namespaceUri = getNamespaceURI(ele);
if (namespaceUri == null) {
return null;
}
//根据用户自定义uri来获取handler
NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
if (handler == null) {
error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
return null;
}
return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}
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