Spring IOC容器刷新BeanFactory（XML配置方式）
Spring IOC容器刷新BeanFactory
前言
Spring IOC容器刷新BeanFactory是一个很复杂的过程，本文将基于XML配置的方式展开分析一下Spring IOC容器刷新BeanFactory的过程，如有误还请指出。
告诉子类刷新内部BeanFactory
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
// 上下文刷新前准备
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
// 告诉子类刷新内部BeanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
// 使用上下文前对bean工厂的一些准备工作
prepareBeanFactory(beanFactory);
// ...省略
}
告诉子类刷新内部BeanFactory
这里做了两件事：
- refreshBeanFactory();刷新bean工厂
- getBeanFactory();获取bean工厂
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
return getBeanFactory();
}
刷新bean工厂
刷新bean工厂主要做了以下几件事
- 如果有bean工厂先销毁和关闭bean工厂
- 创建bean工厂
- bean工厂定制
- 加载bean定义
@Override
protected final void refreshBeanFactory() throws BeansException {
// 1
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
// 2
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
// 3
customizeBeanFactory(beanFactory);
// 4
loadBeanDefinitions(beanFactory);
this.beanFactory = beanFactory;
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
展开看一下加载bean定义
- AbstractXmlApplicationContext重写的loadBeanDefinitions方法
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// 为beanFactory创建一个XmlBeanDefinitionReader
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// 资源加载环境
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
// bean定义阅读器
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// 允许子类提供阅读器的自定义初始化
initBeanDefinitionReader(beanDefinitionReader);
// 加载bean定义
loadBeanDefinitions(beanDefinitionReader);
}
/**
这里做了两件事
1.如果存在根据资源获取bean定义那就根据资源获取
2.如果存在根据配置路径获取bean定义就根据路径记载bean定义
*/
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
// 根据配置资源加载bean定义
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
// 根据配置路径加载bean定义
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}
- 加载bean定义
@Override
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int count = 0;
// 加载bean定义
for (String location : locations) {
count += loadBeanDefinitions(location);
}
// 返回加载bean资源次数
return count;
}
...省略
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
// 资源加载器
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot load bean definitions from location [" + location + "]: no ResourceLoader available");
}
// 资源加载器为资源模式的解析器根据资源加载bean定义
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
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 {
// 根据路径获取资源，并加载bean定义
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;
}
}
这里做了如下的几件事
- 根据配置资源加载bean定义
- 根据配置路径加载bean定义
- 这里我们看一下根据路径加载bean定义
通过XmlBeanDedinitionReader``loadBeanDefinitions方法根据配置路径加载bean定义
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.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());
}
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();
}
}
}
这里主要干了两件事：
- 从XML加载bean定义，这里加载XML的细节我们先不管了，这并非加载bean定义的核心
- 加载bean定义
doLoadBeanDefinitions，干事儿的都是do开头
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
// 加载XML中的bean定义，这里使用的是SAX
Document doc = doLoadDocument(inputSource, resource);
// 注册bean定义
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);
}
}
这里做了两件事：
- 加载XML中的bean定义，这里使用的是SAX
- 注册bean定义
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
// 注册bean定义
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
DefaultBeanDefinitionDocumentReader``registerBeanDefinitions注册bean定义
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
// 获取Element并注册bean定义
doRegisterBeanDefinitions(doc.getDocumentElement());
}
protected void doRegisterBeanDefinitions(Element root) {
// Any nested elements will cause recursion in this method. In
// order to propagate and preserve 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);
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;
}
}
}
preProcessXml(root);
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);
this.delegate = parent;
}
这里主要做了以下几件事：
- 获取Element并注册bean定义
- 解析bean定义前处理
- 解析bean定义
- 解析bean定义后处理
核心的方法parseBeanDefinitions：
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
// 判断是否默认命名空间还是自定义命名空间
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Spring默认标签
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
// 解析自定义元素节点
delegate.parseCustomElement(root);
}
}
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
parseDefaultElement解析默认Spring标签，分别是import,alias,bean,beans
- 以
bean标签为例，看一下如何处理的bean定义
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
// 对bean的属性和里面的子元素进行具体解析，并将属性设置到BeanDefinitionHolder中
// BeanDefinitionHolder是BeanDefinition的封装类，它包含了BeanDefinition
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// 将BeanDefinition注册到BeanFactory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.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
BeanDefinitionParserDelegate``parseBeanDefinitionElement方法解析并获取AbstractBeanDefinition对象
@Nullable
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
...省略
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
... 省略
}
@Nullable
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 {
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
parseMetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
parseConstructorArgElements(ele, bd);
parsePropertyElements(ele, bd);
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;
}
- 转到
BeanDefinitionReaderUtils.registerBeanDefinition代码
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
// DefaultListableBeanFactory registerBeanDefinition方法注册BeanDefinition
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
//
registry.registerAlias(beanName, alias);
}
}
}
DefaultListableBeanFactory``registerBeanDefinition方法注册BeanDefinition
@Override
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);
// 存在BeanDefinition更新beanDefinitionMap
if (existingDefinition != null) {
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 {
// 将beanName和对应的BeanDefinition放到IOC容器的map中
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
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
// 重新设置beanDefinition
resetBeanDefinition(beanName);
}
else if (isConfigurationFrozen()) {
clearByTypeCache();
}
}
总结
Spring IOC刷新BeanFactory刷新bean工厂是一个特别复杂的过程，主要是如果已经存在bean工厂就会先销毁并关闭bean工厂，然后重新创建bean工厂加载BeanDefinition，其加载BeanDefinition主要有根据配置的路径和配置资源两种方式进行加载，本文主要讲的是根据配置的路径进行加载。简单来说，根据路径加载BeanDefinition是通过解析XML文件根据文件的Element标签进行加载BeanDefinition，最后就是将BeanDefinition注册到bean工厂并且放到IOC容器的map中。