概述
一、ClassPathXmlApplicationContext spring上下文,即容器,拥有注册器和bean工厂,调用refresh()方法,该方法最终调用loadBeanDefinitions(String location),然后将加载任务交由XmlBeanDefinitionReader;
二、XmlBeanDefinitionReader bean定义阅读器,拥有ClassPathXmlApplicationContext的bean注册器,使用DefaultBeanDefinitionDocumentReader解析xml文档,并将解析的标签交给BeanDefinitionParserDelegate解析。使用DefaultNamespaceHandlerResolver初始化命名空间处理器Map集合(映射规则在"META-INF/spring.handlers"中以键值对形式定义,各个处理器负责相应标签的解析,parse()方法)。
三、DefaultBeanDefinitionDocumentReader 文档阅读器,能解析xml文件,并将标签交由BeanDefinitionParserDelegate解析,执行doScan()等操作或生成beanDefinition并将beanDefinition注册到ClassPathXmlApplicationContext.beanFactory(因为这同时也是个注册器,作为参数一直在各个类中传递)
四、BeanDefinitionParserDelegate 若为自定义标签(除import、bean、alias、beans)根据标签的namespaceUri匹配NamespaceHandler,NamespaceHandler对标签执行parse()方法解析,若是bean标签则生成beanDefinition注册,否之执行其他操作。否则DefaultBeanDefinitionDocumentReader根据标签调用相应的方法。
- ApplicationContext applicationContext = new ClassPathXmlApplicationContext("application.xml");
- ClassPathXmlApplicationContext.refresh();
- ConfigurableListableBeanFactory beanFactory = AbstractApplicationContext.obtainFreshBeanFactory();
- AbstractApplicationContext.refreshBeanFactory();
- AbstractRefreshableApplicationContext.refreshBeanFactory();
protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
//创建容器的bean工厂
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
//解析并注册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);
}
}
- AbstractXmlApplicationContext.loadBeanDefinitions(beanFactory)
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
//XmlBeanDefinitionReader 此类加载DOM文档并将BeanDefinitionDocumentReader(实际为DefaultBeanDefinitionDocumentReader)应用于该文档。
//BeanDefinitionDocumentReader解析文档后使用给定的beanFactory(DefaultListableBeanFactory,实现BeanDefinitionRegistry接口)注册bean,
//即注册到beanFactory
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context‘s
// resource loading environment.
// environment为spring运行环境,包括一些运行参数等
beanDefinitionReader.setEnvironment(this.getEnvironment());
//ResourceLoader用来加载文件,如.class文件或其它系统文件,可根据路径获得资源抽象Resource和获得classLoader(用来搜索或加载类给jvm使用),
//classLoader可知道包括当前运行环境中的class和package;
//ClassPathXmlApplicationContext继承DefaultResourceLoader
beanDefinitionReader.setResourceLoader(this);
//ResourceEntityResolver 实现 EntityResolver,按照网上的资料,该类是用来查找.dtd约束文件或.schemas约束文件,
//即定义application.xml时引入的约束文件,起规范配置内容的作用
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);
//加载bean定义,实际解析并注册动作
loadBeanDefinitions(beanDefinitionReader);
}
- AbstractXmlApplicationContext.loadBeanDefinitions(beanDefinitionReader)
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
//获取配置文件名application.xml,在构造方法中设置的
String[] configLocations = getConfigLocations();
if (configLocations != null) {
//加载bean定义
reader.loadBeanDefinitions(configLocations);,
}
}
- AbstractBeanDefinitionReader.loadBeanDefinitions(configLocations)
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int count = 0;
for (String location : locations) {
//实际加载过程
count += loadBeanDefinitions(location);
}
return count;
}
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
return loadBeanDefinitions(location, null);
}
- AbstractBeanDefinitionReader.loadBeanDefinitions(location, null)
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
//上面设置的资源加载器
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot load bean definitions from location [" + location + "]: no ResourceLoader available");
}
//ApplicationContext接口实现ResourcePatternResolver接口
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
//返回application.xml抽象实例
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
//加载bean定义
int count = loadBeanDefinitions(resources);
if (actualResources != null) {
Collections.addAll(actualResources, resources);
}
if (logger.isTraceEnabled()) {
logger.trace("Loaded " + count + " bean definitions from location pattern [" + location + "]");
}
return count;
}
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 count = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isTraceEnabled()) {
logger.trace("Loaded " + count + " bean definitions from location [" + location + "]");
}
return count;
}
}
- AbstractBeanDefinitionReader.loadBeanDefinitions(resources);
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int count = 0;
for (Resource resource : resources) {
//加载bean定义
count += loadBeanDefinitions(resource);
}
return count;
}
- XmlBeanDefinitionReader.loadBeanDefinitions(resource)
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
//EncodedResource作用是以特定的encoding或Charset从资源中读取内容
return loadBeanDefinitions(new EncodedResource(resource));
}
- XmlBeanDefinitionReader.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);
}
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 (InputStream inputStream = encodedResource.getResource().getInputStream()) {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//继续
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
- XmlBeanDefinitionReader.doLoadBeanDefinitions(inputSource, encodedResource.getResource())
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
//返回一个文档对象,该对象包含所有application.xml中配置的信息
Document doc = doLoadDocument(inputSource, resource);
// 继续往下
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);
}
}
- XmlBeanDefinitionReader.registerBeanDefinitions(doc, resource)
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
//创建文档阅读器,由上面可知为DefaultBeanDefinitionDocumentReader
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
//获取注册前bean定义数目
int countBefore = getRegistry().getBeanDefinitionCount();
//解析注册bean定义
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
//返回在bean定义读取过程中传递的上下文,封装了所有相关的配置和状态。包括阅读器[有注册器(DefaultListableBeanFactory)]、
//资源(Resource-application.xml)、名称空间处理器解析器(NamespaceHandlerResolver)等
public XmlReaderContext createReaderContext(Resource resource) {
//NamespaceHandlerResolver-DefaultNamespaceHandlerResolver根据映射文件中包含的映射将名称空间URI解析为实现类。
//映射规则在"META-INF/spring.handlers"中以键值对形式定义
//http://www.springframework.org/schema/context -> org.springframework.context.config.ContextNamespaceHandler
//相应的处理器定义了特定的标签如何解析
return new XmlReaderContext(resource, this.problemReporter, this.eventListener,
this.sourceExtractor, this, getNamespaceHandlerResolver());
}
- DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(doc, createReaderContext(resource))
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
//将根标签<beans></beans>作为参数执行解析注册
doRegisterBeanDefinitions(doc.getDocumentElement());
}
- DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions(doc.getDocumentElement())
@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;
//创建一个用于解析的委托类
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;
}
}
}
//解析前处理
preProcessXml(root);
//解析注册
parseBeanDefinitions(root, this.delegate);
//解析后处理
postProcessXml(root);
this.delegate = parent;
}
- DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(root, this.delegate)
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)) {
//解析默认标签,import、bean、alias、beans
parseDefaultElement(ele, delegate);
}
else {
//其它标签
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
- DefaultBeanDefinitionDocumentReader.parseDefaultElement(ele, delegate) 解析默认标签
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
//<import></import>
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
//<alias></alias>
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
//<bean></bean>
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
//<beans></beans>
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
- BeanDefinitionParserDelegate.parseCustomElement(ele);解析自定义标签
public BeanDefinition parseCustomElement(Element ele, @Nullable BeanDefinition containingBd) {
//查找,名称空间路径(每个标签具有的属性,直接获取)
String namespaceUri = getNamespaceURI(ele);
if (namespaceUri == null) {
return null;
}
//通过路径匹配相应的处理器
NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
if (handler == null) {
error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
return null;
}
//调用处理器解析标签,执行相应的操作或生成bean定义,如 <context:component-scan base-package="com.jty.controller"/>,
//则执行doScan方法扫描标注解的类然后注册,源代码如下
//ClassPathBeanDefinitionScanner scanner = configureScanner(parserContext, element);
//Set<BeanDefinitionHolder> beanDefinitions = scanner.doScan(basePackages);
//registerComponents(parserContext.getReaderContext(), beanDefinitions, element);
return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}
- processBeanDefinition(ele, delegate); 解析bean标签
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//解析bean标签返回BeanDefinitionHolder,包含bean name、别名、BeanDefinition
//
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
//阅读器中的注册器将BeanDefinition注册到BeanDefinition Map,至此bean解析注册结束
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));
}
}
- BeanDefinitionParserDelegate.parseBeanDefinitionElement(ele)
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
//获取标签id作为name
String id = ele.getAttribute(ID_ATTRIBUTE);
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
//解析别名
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);
}
//获取bean标签中class属性创建、初始化beanDefinition返回
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;
}