Spring源码学习笔记之基于ClassPathXmlApplicationContext进行bean标签解析
bean 标签在spring的配置文件中, 是非常重要的一个标签, 即便现在boot项目比较流行, 但是还是有必要理解bean标签的解析流程,有助于我们进行
基于注解配置, 也知道各个标签的作用,以及是怎样被spring识别的, 以及配置的时候需要注意的点.
传统的spring项目,spring内部启动的方式是基于ClassPathXmlApplicationContext启动的:
@Test
public void test1() {
//传入spring的配置文件路径
ApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext("spring.xml");
System.out.println("");
}
// 调用有参构造,设置spring配置文件的位置
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
this(new String[] {configLocation}, true, null);
}
//进一步跟进
public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
// 此处parent 为null
super(parent);
//创建解析器，解析configLocations
setConfigLocations(configLocations);
// refresh = true
if (refresh) {
//刷新spring容器,bean标签的核心方法
refresh();
}
}
//进一步跟进refresh 方法
public Collection<ApplicationListener<?>> getApplicationListeners() {
return this.applicationListeners;
}
/*
* 该方法是spring容器初始化的核心方法。是spring容器初始化的核心流程，是一个典型的父类模板设计模式的运用
* 根据不同的上下文对象，会掉到不同的上下文对象子类方法中
*
* 核心上下文子类有：
* ClassPathXmlApplicationContext
* FileSystemXmlApplicationContext
* AnnotationConfigApplicationContext
* EmbeddedWebApplicationContext(springboot)
*
* 方法重要程度：
* 0：不重要，可以不看
* 1：一般重要，可看可不看
* 5：非常重要，一定要看
* */
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//为容器初始化做准备，重要程度：0
// Prepare this context for refreshing.
prepareRefresh();
/*
重要程度：5
1、创建BeanFactory对象
* 2、xml解析
* 传统标签解析：bean、import等
* 自定义标签解析 如：<context:component-scan base-package="com.xiangxue.jack"/>
* 自定义标签解析流程：
* a、根据当前解析标签的头信息找到对应的namespaceUri
* b、加载spring所以jar中的spring.handlers文件。并建立映射关系
* c、根据namespaceUri从映射关系中找到对应的实现了NamespaceHandler接口的类
* d、调用类的init方法，init方法是注册了各种自定义标签的解析类
* e、根据namespaceUri找到对应的解析类，然后调用paser方法完成标签解析
*
* 3、把解析出来的xml标签封装成BeanDefinition对象
* */
// Tell the subclass to refresh the internal bean factory.
//此处创建bean 工厂, 解析bean 标签以及处理 component-scan 标签的核心方法
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();
}
}
}
//进一步跟进创建bean工厂的方法obtainFreshBeanFactory,研究bean 标签的解析逻辑
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
//核心方法，必须读，重要程度：5
refreshBeanFactory();
return getBeanFactory();
}
//再一步跟进refreshBeanFactory 方法
跟到这里,我们发现分叉了, 有 多个实现类, 那么是跟哪一个呢?
这个是使我们看一下类的继承关系图
很明显这个时候我们再次跟进的时候需要看的跟的就是org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory ,我们再次跟踪
@Override
protected final void refreshBeanFactory() throws BeansException {
//如果BeanFactory不为空，则清除BeanFactory和里面的实例
// 由于我们的容器刚启动,所以这里自然也是false
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
//创建DefaultListableBeanFactory
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
//设置是否可以循环依赖 allowCircularReferences
//是否允许使用相同名称重新注册不同的bean实现.
customizeBeanFactory(beanFactory);
//解析xml，并把xml中的标签封装成BeanDefinition对象
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
// 进一步跟进spring容器加载beandefinition对象的过程
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
//创建xml的解析器，这里是一个委托模式
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(this.getEnvironment());
//这里传一个this进去，因为ApplicationContext是实现了ResourceLoader接口的
beanDefinitionReader.setResourceLoader(this);
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);
//主要看这个方法 重要程度 5
loadBeanDefinitions(beanDefinitionReader);
}
设置资源加载器设置了this 对象象,这是因为当前对象是.AbstractRefreshableApplicationContext,继承自DefaultResourceLoader,
而DefaultResourceLoader 实现了Resourloader 接口
接着上面的源码,进一步跟进核心方法loadBeanDefinitions :
//这里需要我们回忆一下我们最初的构造器,参数是设置到 configLocation 里面去了,所以这里设置核心关注点在从configLocations 中解析xml文件,解析bean标签
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
//获取需要加载的xml配置文件
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}
//进一步跟进loadBeanDefinitions(String args) 这个方法
@Override
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int count = 0;
//配置文件有多个，加载多个配置文件
for (String location : locations) {
//这里的数量是beandefination的数量
count += loadBeanDefinitions(location);
}
return count;
}
//再进一步跟进
@Override
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
return loadBeanDefinitions(location, null);
}
//在进一步跟进
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot load bean definitions from location [" + location + "]: no ResourceLoader available");
}
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
//把字符串类型的xml文件路径，形如：classpath*:user/**/*-context.xml,转换成Resource对象类型，其实就是用流
//的方式加载配置文件，然后封装成Resource对象，不重要，可以不看
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
//主要看这个方法 ** 重要程度 5
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;
}
}
// 再进一步跟踪loadBeanDefinitions 方法
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot load bean definitions from location [" + location + "]: no ResourceLoader available");
}
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
//把字符串类型的xml文件路径，形如：classpath*:user/**/*-context.xml,转换成Resource对象类型，其实就是用流
//的方式加载配置文件，然后封装成Resource对象，不重要，可以不看
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
//主要看这个方法 ** 重要程度 5
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;
}
}
// 进一步跟踪loadBeanDefinitions(resources) 方法
由于代码很深, 跟着跟着很有可能就跟丢了,这个时候debug 一下:
那么我们继续
// 进一步跟踪loadBeanDefinitions(resources) 方法
@Override
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int count = 0;
for (Resource resource : resources) {
//模板设计模式，调用到子类中的方法
count += loadBeanDefinitions(resource);
}
return count;
}
// 再 进一步跟踪
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
//EncodedResource带编码的对Resource对象的封装
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);
}
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 {
//获取Resource对象中的xml文件流对象
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
//InputSource是jdk中的sax xml文件解析对象
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//主要看这个方法 ** 重要程度 5
// 这里才是真正开始解析,封装beanDifination对象
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();
}
}
}
//进一步跟踪如下
// 加载xml,解析document,将其中的元素封装为beandefinition 并注册
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
//把inputSource 封装成Document文件对象，这是jdk的API
Document doc = doLoadDocument(inputSource, resource);
//主要看这个方法，根据解析出来的document对象，拿到里面的标签元素封装成BeanDefinition
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);
}
}
//进一步跟踪源代码
// 创建reader 读取document,并将其封装为 beandefination,以及并注册
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
//又来一记委托模式，BeanDefinitionDocumentReader委托这个类进行document的解析
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
//主要看这个方法，createReaderContext(resource) XmlReaderContext上下文，封装了XmlBeanDefinitionReader对象
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
其中部分调用方法简单做一下分析
//public XmlReaderContext createReaderContext(Resource resource) {
// return new XmlReaderContext(resource, this.problemReporter, this.eventListener,
//获取命名空间解析器,后续用来判断是否默认的名称空间, 针对不同的名称空间进行处理
// this.sourceExtractor, this, getNamespaceHandlerResolver());
//}
// 回到主流程进行进一步分析,以及跟踪
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
//主要看这个方法，把root节点传进去
doRegisterBeanDefinitions(doc.getDocumentElement());
}
// 此时传入的元素为根元素
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.
//创建BeanDefinitionParser 的委托类,并进行默认属性的的设置
// 如果bean的属性没有设置,则使用默认值得默认属性
BeanDefinitionParserDelegate parent = this.delegate;
this.delegate = createDelegate(getReaderContext(), root, parent);
//判断是否默认的命名空间的依据是否是beans开始的,开始的则是默认的命名空间 否则就不是
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;
}
}
}
// 前置处理
preProcessXml(root);
//主要看这个方法，标签具体解析过程
parseBeanDefinitions(root, this.delegate);
// 后置处理 模板设计模式 , springmvc 中的interceptor
postProcessXml(root);
this.delegate = parent;
}
<em id="__mceDel"> </em>
在这里我们需要留意一下创建解析方法,其中有做默认属性的处理
//开始解析元素, 根据命名空间是否默认命名空间,解析方式不一样
// 其中涉及到bean 解析的其实是两种都有设计到, bean 标签没带前缀,为默认命名空
// 开启注解的<context:component-scan= "basepacakge "> 非默认的命名空间
// 我们的bean 标签不属于自定义标签
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)) {
//默认标签解析
parseDefaultElement(ele, delegate);
}
else {
//自定义标签解析
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
//这里我们先跟踪bean 基于xml的bean 标签解析
// bean 标签属于默认标签
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
//import标签解析 重要程度 1 ，可看可不看
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
//alias标签解析 别名标签 重要程度 1 ，可看可不看
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
//bean标签，重要程度 5，必须看
// 如果是bean 标签,则进步解析为beanDefinition 对象
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
//解析bean 标签并封装成beandefinitionHolder 对象
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//重点看这个方法，重要程度 5 ，解析document，封装成BeanDefinition
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
//该方法功能不重要，设计模式重点看一下，装饰者设计模式，加上SPI设计思想
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
//完成document到BeanDefinition对象转换后，对BeanDefinition对象进行缓存注册
// Register the final decorated instance.
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));
}
}
//进一步跟踪
@Nullable
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
return parseBeanDefinitionElement(ele, null);
}
//进一步跟踪
@Nullable
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;
// 当bean 为空, 并且 别名不为空的情况下, 取第一个别名作为bean的别名
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");
}
}
//检查beanName是否重复
if (containingBean == null) {
checkNameUniqueness(beanName, aliases, ele);
}
// 核心方法.解析元素封装为beandefinition对象
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 {
// 如果即没有name 属性也没有id 属性,此时bean没有名称
// 这里生成beanName
// xml 方式的beanName 为 全限定命名#数字 如果 com.test.Student#0
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;
}
//进一步跟踪封装成为beanDefinition对象的全过程
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, @Nullable BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
// 获取class 属性
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
// 获取parent 属性
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
try {
//创建GenericBeanDefinition对象
// 这里的beandefinition 对象是GenericBeanDefinition
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
//解析bean标签的属性，并把解析出来的属性设置到BeanDefinition对象中
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
//解析bean中的meta标签
parseMetaElements(ele, bd);
//解析bean中的lookup-method标签 重要程度：2，可看可不看
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
//解析bean中的replaced-method标签 重要程度：2，可看可不看
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
//解析bean中的constructor-arg标签 重要程度：2，可看可不看
parseConstructorArgElements(ele, bd);
//解析bean中的property标签 重要程度：2，可看可不看
parsePropertyElements(ele, bd);
//可以不看，用不到
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;
}
// 属性解析的逻辑
public AbstractBeanDefinition parseBeanDefinitionAttributes(Element ele, String beanName,
@Nullable BeanDefinition containingBean, AbstractBeanDefinition bd) {
if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
error("Old 1.x 'singleton' attribute in use - upgrade to 'scope' declaration", ele);
}
// 解析scope 属性
else if (ele.hasAttribute(SCOPE_ATTRIBUTE)) {
bd.setScope(ele.getAttribute(SCOPE_ATTRIBUTE));
}
else if (containingBean != null) {
// Take default from containing bean in case of an inner bean definition.
bd.setScope(containingBean.getScope());
}
// 解析abstract 属性
if (ele.hasAttribute(ABSTRACT_ATTRIBUTE)) {
bd.setAbstract(TRUE_VALUE.equals(ele.getAttribute(ABSTRACT_ATTRIBUTE)));
}
// 从解析委托类中获取默认属性值lazy_init
String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE);
if (DEFAULT_VALUE.equals(lazyInit)) {
lazyInit = this.defaults.getLazyInit();
}
bd.setLazyInit(TRUE_VALUE.equals(lazyInit));
String autowire = ele.getAttribute(AUTOWIRE_ATTRIBUTE);
bd.setAutowireMode(getAutowireMode(autowire));
// depends-on 属性
if (ele.hasAttribute(DEPENDS_ON_ATTRIBUTE)) {
String dependsOn = ele.getAttribute(DEPENDS_ON_ATTRIBUTE);
bd.setDependsOn(StringUtils.tokenizeToStringArray(dependsOn, MULTI_VALUE_ATTRIBUTE_DELIMITERS));
}
String autowireCandidate = ele.getAttribute(AUTOWIRE_CANDIDATE_ATTRIBUTE);
if ("".equals(autowireCandidate) || DEFAULT_VALUE.equals(autowireCandidate)) {
String candidatePattern = this.defaults.getAutowireCandidates();
if (candidatePattern != null) {
String[] patterns = StringUtils.commaDelimitedListToStringArray(candidatePattern);
bd.setAutowireCandidate(PatternMatchUtils.simpleMatch(patterns, beanName));
}
}
else {
bd.setAutowireCandidate(TRUE_VALUE.equals(autowireCandidate));
}
//这个primary 属性
if (ele.hasAttribute(PRIMARY_ATTRIBUTE)) {
bd.setPrimary(TRUE_VALUE.equals(ele.getAttribute(PRIMARY_ATTRIBUTE)));
}
// init-method 属性
if (ele.hasAttribute(INIT_METHOD_ATTRIBUTE)) {
String initMethodName = ele.getAttribute(INIT_METHOD_ATTRIBUTE);
bd.setInitMethodName(initMethodName);
}
else if (this.defaults.getInitMethod() != null) {
bd.setInitMethodName(this.defaults.getInitMethod());
bd.setEnforceInitMethod(false);
}
//destory-method
if (ele.hasAttribute(DESTROY_METHOD_ATTRIBUTE)) {
String destroyMethodName = ele.getAttribute(DESTROY_METHOD_ATTRIBUTE);
bd.setDestroyMethodName(destroyMethodName);
}
else if (this.defaults.getDestroyMethod() != null) {
bd.setDestroyMethodName(this.defaults.getDestroyMethod());
bd.setEnforceDestroyMethod(false);
}
//factory-method
if (ele.hasAttribute(FACTORY_METHOD_ATTRIBUTE)) {
bd.setFactoryMethodName(ele.getAttribute(FACTORY_METHOD_ATTRIBUTE));
}
//factory-bean 属性
if (ele.hasAttribute(FACTORY_BEAN_ATTRIBUTE)) {
bd.setFactoryBeanName(ele.getAttribute(FACTORY_BEAN_ATTRIBUTE));
}
return bd;
}
//到此,spring 解析bean 标签基本完后,我们在回过去看bean标签解析完成后,做了什么处理
//beandefinition 解析完成后,注册到bean 注册中心中去,后续实例化的时候再去取用
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
//完成BeanDefinition的注册，重点看，重要程度 5
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
//建立别名和 id的映射，这样就可以根据别名获取到id
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
// 注册beandefinitionholder 到bean 注册中心中
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
//完成BeanDefinition的注册，重点看，重要程度 5
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
//建立别名和 id的映射，这样就可以根据别名获取到id
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
至此,bean 标签的解析流程基本结束, 如果用流程图表示整个过程的话,整个过程的整体流程如图所示:
后续会继续完善开启注解扫描部分的讲解.即<context:component-scan="basepackage"> 标签的解析流程.
正文到此结束
- 本文标签： final message springboot 缓存 tab description 空间 DOM 参数 Listeners id Qualifier 源码 tar 设计模式 Document SpringMVC ACE Collection synchronized classpath 代码 parse list strace IO equals root https API 解析 value http cache ArrayList 自定义标签 web struct IDE HTML XML core bean 注册中心 tag spring ip UI App Collections entity Property token HashSet db 配置 CTO src BeanDefinition bug stream node cat CEO 实例
- 版权声明： 本文为互联网转载文章，出处已在文章中说明(部分除外)。如果侵权，请联系本站长删除，谢谢。
- 本文海报： 生成海报一 生成海报二
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文章和留言都翻到11页了 没有OOM
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朋友，翻页到11页，及以后，会出现OOM，无法访问
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搞个gitee的项目
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版本号是多少，你可以下载哪个代码仓库，jdk选1.8 直接跑就行
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