先来看看代码，还是先从FileSystemXmlApplicationContext的构造方法入手，前面俩个方法均已讲解过，最后讲解refresh()方法。
public FileSystemXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
来看看refresh方法的代码，后面顺着往下讲好了。
public abstract class AbstractApplicationContext extends DefaultResourceLoader
implements ConfigurableApplicationContext {
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
//刷新前的前置准备，更改容器的激活还有关闭状态，另外初始化需要加载的文本。
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
//新建Bean工厂，同时对bean进行注册
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
//bean工厂使用之前的准备工作
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
//bean工厂的后置处理，由子类去实现。这里并没有任何子类去实现
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
//bean工厂的后置处理
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
//注册bean的后置处理器
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
//初始化容器的EventMulticaster，可以处理事件以及监听器的对应关系
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
//提供给子类去实现的一个方法
onRefresh();
// Check for listener beans and register them.
//注册监听器
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
//完成bean工厂的初始化
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
//完成刷新
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();
}
}
}
}
prepareRefresh();主要是做刷新前的一些前置准备
obtainFreshBeanFactory();创建bean工厂，并且对bean实例进行注册, 随后将工厂实例返回。
还有后续的一些方法，后面再讲解，优先讲解怎么对bean实例进行注册，所以针对obtainFreshBeanFactory()方法。下面看看其方法的代码
/**
* Tell the subclass to refresh the internal bean factory.
* @return the fresh BeanFactory instance
* @see #refreshBeanFactory()
* @see #getBeanFactory()
*/
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
从代码得知，首先是刷新BeanFactory,其次再获得beanFactory()
那么先看看refreshBeanFactory()方法是如何执行的。
public abstract class AbstractRefreshableApplicationContext extends AbstractApplicationContext {
/**
* This implementation performs an actual refresh of this context's underlying
* bean factory, shutting down the previous bean factory (if any) and
* initializing a fresh bean factory for the next phase of the context's lifecycle.
*/
@Override
protected final void refreshBeanFactory() throws BeansException {
//判断工厂存不存在，存在则进行摧毁，一开始肯定是不存在的，因此往下走
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
//创建bean工厂
DefaultListableBeanFactory beanFactory = createBeanFactory();
//设置序列化id,避免重复创建
beanFactory.setSerializationId(getId());
//定义bean工厂
customizeBeanFactory(beanFactory);
//读取BeanDefinition，并且注测到beanFactory中去
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
//将bean工厂注入到成员变量中去，后续获取beanFac直接从成员变量获取即可
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
}
从refreshBeanFactory()中的代码中看出，loadBeanDefinitions(beanFactory)才是将bean注册到BeanFac的关键。下面看看loadBeanDefinitions(beanFactory)方法的实现。
public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext {
/**
* Loads the bean definitions via an XmlBeanDefinitionReader.
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
* @see #initBeanDefinitionReader
* @see #loadBeanDefinitions
*/
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
//创建beanDefinitionReader，同时将beanDefinitionReader与beanFactory建立起关系
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
beanDefinitionReader.setEnvironment(this.getEnvironment());
//beanDefinitionReader跟资源加载器建立关系，this实例本身就是ResourceLoader的子类，所以直接作为成品变量，建立起关系
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
//初始化
initBeanDefinitionReader(beanDefinitionReader);
//加载BeanDefinitions
loadBeanDefinitions(beanDefinitionReader);
}
}
从AbstractXmlApplicationContext的loadBeanDefinitions方法中可以看出，首先会创建一个XmlBeanDefinitionReader同时与beanFactory建立关系，其次XmlBeanDefinitionReader再与resourceLoader建立关系(容器本身便是资源加载器，同时也保存了路径)，最后通过XmlBeanDefinitionReader去加载BeanDefinitions即可，那么XmlBeanDefinitionReader要做的事情，便是根据路径，利用资源加载器去加载，最后将resource转化成BeanDefinition，并且注册到beanFactory。那么下面看看loadBeanDefinitions(beanDefinitionReader)是怎么加载的
public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext {
/**
* Load the bean definitions with the given XmlBeanDefinitionReader.
* <p>The lifecycle of the bean factory is handled by the {@link #refreshBeanFactory}
* method; hence this method is just supposed to load and/or register bean definitions.
* @param reader the XmlBeanDefinitionReader to use
* @throws BeansException in case of bean registration errors
* @throws IOException if the required XML document isn't found
* @see #refreshBeanFactory
* @see #getConfigLocations
* @see #getResources
* @see #getResourcePatternResolver
*/
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
//该方法是由子类去实现的，可以自己注入一些resource让容器去加载,因为没有实现该接口方法，所以的话，当然就没有资源，最后只能通过路径去获取资源
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
//获取父类AbstractRefreshableConfigApplicationContext保存的路径变量，其实说白了就是经过处理的路径值，就是我们构造方法传进去的路径值
String[] configLocations = getConfigLocations();
if (configLocations != null) {
//reader根据路径去加载beanDefinitions
reader.loadBeanDefinitions(configLocations);
}
}
}
根据上述代码，最后果然是根据路径来加载BeanDefinition，那么再往深一层走
public abstract class AbstractBeanDefinitionReader implements EnvironmentCapable, BeanDefinitionReader {
@Override
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int counter = 0;
for (String location : locations) {
//这个方法是关键，获取到了注册到beanFac的bean数量,再往下走
counter += loadBeanDefinitions(location);
}
return counter;
}
}
@Override
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
//再往下走
return loadBeanDefinitions(location, null);
}
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
//获取资源加载器，也就是容器本身
ResourceLoader resourceLoader = getResourceLoader();
//因为已经注入到成员变量了，所以肯定是不可能为空的
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
}
//进行类型判断，FileSystemXmlApplicationContext恰好是ResourcePatternResolver的子类，因此只需要关注该分支代码即可。
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
//根据路径获取资源
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
//将资源转化成BeanDefinition并且加载到BeanFac
int loadCount = loadBeanDefinitions(resources);
...剩下到逻辑与核心逻辑无关
return loadCount;
}
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 loadCount = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
}
}
根据上述代码，最核心的有俩个方法，就是根据路径获取Resource，最后根据Resource来转化成BeanDefinitions并且注册到BeanFactory.
image.png
那么怎么将Resource来转化成BeanDefinitions并且注册到BeanFactory呢
public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
//将resource转成EncodedResource,定义了资源的编码格式，直接看该方法内部实现
return loadBeanDefinitions(new EncodedResource(resource));
}
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
//避免线程重复加载资源，同时将资源存储到线程变量中去
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
//通过资源获取到对应的字节流，因为之前有路径了，后面当然是要读取spring的xml配置文件
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
//包装成inputSource，设置编码格式
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//do才是真正开始做事情，开始加载
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();
}
}
}
/**
* 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 {
//读取文件，并且将内容转化成document，这里方式有好多...里面内容复杂，就跳过
Document doc = doLoadDocument(inputSource, resource);
//注册BeanDefinitions
return registerBeanDefinitions(doc, resource);
}
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);
}
}
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
//获取注册前的数量,XmlBeanDefinitionReader之前已经跟beanFac建立了关系，因此可以知道beanFac中注册的BeanDefinition的数量
int countBefore = getRegistry().getBeanDefinitionCount();
//注册方法--核心
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
//注册后的数量-注册前的数量便是注册的bean的数量
return getRegistry().getBeanDefinitionCount() - countBefore;
}
}
从上述代码走读下来，发现很长一大串，但是核心思想最后就是根据resource去加载xml配置文件，最后生成doc，当然最后要根据doc生成成beanDefinition，那么怎么生成这就是documentReader去实现的了。documentReader.registerBeanDefinitions(doc, createReaderContext(resource))便实现了这个逻辑。接下里往下走
public class DefaultBeanDefinitionDocumentReader implements BeanDefinitionDocumentReader {
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
//获取根元素，并且进行注册
doRegisterBeanDefinitions(root);
}
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);
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);
if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
if (logger.isInfoEnabled()) {
logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec +
"] not matching: " + getReaderContext().getResource());
}
return;
}
}
}
preProcessXml(root);
//开始根据rootElement来解析，这里可能需要看看xml解析的相关知识
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);
this.delegate = parent;
}
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
if (delegate.isDefaultNamespace(root)) {
//获取子元素，进行遍历
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;
//判断元素的名称空间是否为默认的名称空间，这里显然不会是
if (delegate.isDefaultNamespace(ele)) {
parseDefaultElement(ele, delegate);
}
else {
//由于测试的配置文件中,本人只配置了扫描 <context:component-scan base-package="com.gee"></context:component-scan>，debug的时候该元素的属性[annotation-config="true", base-package="com.gee", use-default-filters="true"]，随后往下走,若是直接在xml中配置了bean标签，则路径则完全不一样。执行的是parseDefaultElement(ele, delegate)
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
//那么先简单看看xml中配置的bean标签是如何注册的
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)) {
//标签类型为bean标签，直接将元素
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//bean标签中由于已经指定了名字跟class所以直接包装成BeanDefinitionHolder即可,注册的方法都是通用的，使用注解跟xml进行注入并无区别，所以BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry())这个方法后面再看
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
//直接将BeanDefinitionHolder注册到BeanFac中去即可
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));
}
}
}
从上述代码来看，便是获取到root元素之后，获取子元素，进行解析，核心便是 delegate.parseCustomElement(ele)，那么看看这个方法如何实现。
public class BeanDefinitionParserDelegate {
@Nullable
public BeanDefinition parseCustomElement(Element ele) {
return parseCustomElement(ele, null);
}
@Nullable
public BeanDefinition parseCustomElement(Element ele, @Nullable BeanDefinition containingBd) {
//名称空间http://www.springframework.org/schema/context
String namespaceUri = getNamespaceURI(ele);
if (namespaceUri == null) {
return null;
}
//根据名称空间获取名称空间处理器，XmlReaderContext已经存储了各个名称空间对应的处理器，所以只要知道哪个名称空间，便知道用哪个处理器去处理，像一种策略模式。
NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
if (handler == null) {
error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
return null;
}
//处理器去解析该元素
return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}
}
从上述代码可以得知，spring是根据元素的名称空间来决定用哪个名称空间处理解析器去解析的，那么<context:component-scan base-package="com.gee"></context:component-scan>标签如何解析呢。接下来往下走
public abstract class NamespaceHandlerSupport implements NamespaceHandler {
@Override
@Nullable
public BeanDefinition parse(Element element, ParserContext parserContext) {
//找到元素的beanDefinitionParser，其实现也是跟找名称空间处理器的逻辑类似，像一种策略模式，根据标签的名字找到对应的解析器。
BeanDefinitionParser parser = findParserForElement(element, parserContext);
//最后元素解析器进行解析
return (parser != null ? parser.parse(element, parserContext) : null);
}
@Nullable
private BeanDefinitionParser findParserForElement(Element element, ParserContext parserContext) {
String localName = parserContext.getDelegate().getLocalName(element);
//this.parsers中的key-vlaue
//property-override=org.springframework.context.config.PropertyOverrideBeanDefinitionParser@50a638b5
//annotation-config=org.springframework.context.annotation.AnnotationConfigBeanDefinitionParser@1817d444
//mbean-server=org.springframework.context.config.MBeanServerBeanDefinitionParser@6ca8564a
//component-scan=org.springframework.context.annotation.ComponentScanBeanDefinitionParser@636be97c----我们这里用到的当然是这个解析器了。。。还有其他就不一一列举了。
BeanDefinitionParser parser = this.parsers.get(localName);
if (parser == null) {
parserContext.getReaderContext().fatal(
"Cannot locate BeanDefinitionParser for element [" + localName + "]", element);
}
return parser;
}
}
从上述代码看出，说白了最后是由ComponentScanBeanDefinitionParser来解析元素。
因此直接往下走。看看是怎么解析的
public class ComponentScanBeanDefinitionParser implements BeanDefinitionParser {
@Override
@Nullable
public BeanDefinition parse(Element element, ParserContext parserContext) {
//获取标签中的包的路径,base-package=com.gee
String basePackage = element.getAttribute(BASE_PACKAGE_ATTRIBUTE);
basePackage = parserContext.getReaderContext().getEnvironment().resolvePlaceholders(basePackage);
String[] basePackages = StringUtils.tokenizeToStringArray(basePackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
// 找到扫描器--扫描器里面的内容其实是根据类有没有@component的直接来决定该类是不是需要由spring管理
ClassPathBeanDefinitionScanner scanner = configureScanner(parserContext, element);
// 扫描器找到包下需要注册的Bean，并且注册
Set<BeanDefinitionHolder> beanDefinitions = scanner.doScan(basePackages);
registerComponents(parserContext.getReaderContext(), beanDefinitions, element);
return null;
}
}
public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider {
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
//根据包名找到候选者组件，被我们用spring组件注解标记的，往下走直接看实现，看看如何生成BeanDefinition
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
//将definitionHolder注册到容器中,scanner的registry是从readContext中获取的
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
//这个方法是如何实现的，后面再讲好了。先直接看registerBeanDefinition方法
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
}
else {
return scanCandidateComponents(basePackage);
}
}
protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {
//直接看工具类的方法，直接往下走
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);
}
}
public class BeanDefinitionReaderUtils {
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
//到bean工厂注册，以beanName-BeanDefinition的key-value方式，看看其内部实现
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
//如果有别名，则注册别名
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
}
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
@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 oldBeanDefinition;
oldBeanDefinition = this.beanDefinitionMap.get(beanName);
//判断该bean是否已经注册过
if (oldBeanDefinition != null) {
//若已经注册过，且不允许覆盖，则直接抛异常
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + oldBeanDefinition + "] bound.");
}
else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (this.logger.isWarnEnabled()) {
this.logger.warn("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
oldBeanDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(oldBeanDefinition)) {
if (this.logger.isInfoEnabled()) {
this.logger.info("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + oldBeanDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + oldBeanDefinition +
"] with [" + beanDefinition + "]");
}
}
//r如果注册过，且不是同一个对象则直接覆盖
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
//此时注册都还没有注册，因此当然不可能正在创建中，走另外一个分支代码
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 {
//最后加入到注册列表中去
this.beanDefinitionMap.put(beanName, beanDefinition);
//保存已经注册的bean名称集合中去
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (oldBeanDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}
}
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