我们先用xml加载的方式看下spring bean加载的整个过程。
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">
<!-- 使用设值注入方式装配Person实例 -->
<bean id="person" class="com.example.demo.beans.Person">
<property name="name" value="zhangsan"/>
<property name="age" value="20"/>
</bean>
</beans>
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:spring-beans.xml");
public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
通过指定的parent ApplicationContext(这里为空)创建一个ClassPathXmlApplicationContext,configLocations即为“classpath:spring-beans.xml”,refresh为true。setConfigLocations主要将configLocations赋值给AbstractRefreshableConfigApplicationContext,后面解析xml文件时会从这里来取文件路径。
refresh()方法是本篇Bean加载核心方法,先看下refresh内部的主要方法。
public void refresh() throws BeansException, IllegalStateException {
// private final Object startupShutdownMonitor = new Object();
// 创建了一个对象专门作为容器的刷新(refresh)和销毁(destroy)的同步锁
synchronized (this.startupShutdownMonitor) {
// refresh的前置准备,这里主要是为ApplicationContext的成员变量做默认的赋值操作
prepareRefresh();
// 创建BeanFactory,并解析xml配置文件定义bean,核心方法,后面做详细介绍
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// BeanFactory的前置准备
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();
}
}
}
一、BeanFactory的创建
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
return getBeanFactory();
}
@Override
protected final void refreshBeanFactory() throws BeansException {
// 通过同步锁Object beanFactoryMonitor = new Object()判断BeanFactory是否为null
if (hasBeanFactory()) {
// 如果BeanFactory当前不为null,先销毁和关闭BeanFactory
destroyBeans();
closeBeanFactory();
}
try {
// 创建一个DefaultListableBeanFactory,记住这个BeanFactory
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
// 给两个成员变量赋值
// allowBeanDefinitionOverriding=true 允许BeanDefinition重写
// allowCircularReferences=true 允许循环依赖
customizeBeanFactory(beanFactory);
// 加载和解析配置文件,创建BeanDefinition,重要方法
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// 创建XmlBeanDefinitionReader解析xml文件
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(this.getEnvironment());
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);
// 重要,加载BeanDefinition
loadBeanDefinitions(beanDefinitionReader);
}
解析xml这里用了一系列的loadBeanDefinitions重载方法,这里不一一看了,直接看最后解析的过程。
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 {
// EncodedResource加载了spring-beans.xml
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// 从inputStream中解析创建BeanDefinition,重要
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();
}
}
}
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
// 解析xml获取的Document
Document doc = doLoadDocument(inputSource, resource);
// 从Document中获取数据注册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);
}
}
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
// 注册BeanDefinitiion
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
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xml标签元素
parseDefaultElement(ele, delegate);
}
else {
// 解析自定义标签元素
delegate.parseCustomElement(ele);
}
}
}
}
else {
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)) {
// 这里我们主要看解析xml中Bean标签元素
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// 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));
}
}
这里主要分为三步:
- BeanDefinitionParserDelegate.parseBeanDefinitionElement(ele)
- BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
delegate.parseBeanDefinitionElement(ele)
BeanDefinitionParserDelegate中包含xml bean节点中的各个元素,主要用于xml中bean节点的解析,然后创建BeanDefinition。
@Nullable
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
// 获取id元素的值
String id = ele.getAttribute(ID_ATTRIBUTE);
// 获取name元素的值
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
// 处理别名
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()) {
// 如果id为空,但是有别名,beanName就为别名
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) {
// 判断beanName和别名是否已存在,如果存在就报错否则加入到usedNames集合用于其他beanName的唯一性判断
checkNameUniqueness(beanName, aliases, ele);
}
// 创建BeanDefinition
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);
// 通过BeanDefinition创建BeanDefinitionHolder
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}
return null;
}
在看上面这个方法中具体创建BeanDefinition的过程。
@Nullable
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, @Nullable BeanDefinition containingBean) {
// 根据BeanName创建了一个BeanEntry放到了LikedList中
this.parseState.push(new BeanEntry(beanName));
String className = null;
// 获取class元素的值
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BeanDefinition
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;
}
// parseState.push
public final class ParseState {
/**
* 内部有一个LinkedList,Entry的实现类有BeanEntry
* 对外的push/pop/peek都有内部的这个LinkedList实现。
*/
private final LinkedList<Entry> state;
}
// BeanEntry
public class BeanEntry implements ParseState.Entry {
private String beanDefinitionName;
}
// 使用BeanDefinitionReaderUtils创建BeanDefinition
public static AbstractBeanDefinition createBeanDefinition(
@Nullable String parentName, @Nullable String className, @Nullable ClassLoader classLoader) throws ClassNotFoundException {
GenericBeanDefinition bd = new GenericBeanDefinition();
bd.setParentName(parentName);
if (className != null) {
if (classLoader != null) {
bd.setBeanClass(ClassUtils.forName(className, classLoader));
}
else {
bd.setBeanClassName(className);
}
}
return bd;
}
// 解析xml bean中的其他元素
public AbstractBeanDefinition parseBeanDefinitionAttributes(Element ele, String beanName,
@Nullable BeanDefinition containingBean, AbstractBeanDefinition bd) {
if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
// 1.X版本设置单例Bean,告警
error("Old 1.x 'singleton' attribute in use - upgrade to 'scope' declaration", ele);
}
else if (ele.hasAttribute(SCOPE_ATTRIBUTE)) {
// 设置scope,有singleton(单例Bean)/prototype(原型Bean)/request/session,后两种web中使用
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());
}
if (ele.hasAttribute(ABSTRACT_ATTRIBUTE)) {
bd.setAbstract(TRUE_VALUE.equals(ele.getAttribute(ABSTRACT_ATTRIBUTE)));
}
// 是否懒加载
String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE);
if (isDefaultValue(lazyInit)) {
lazyInit = this.defaults.getLazyInit();
}
bd.setLazyInit(TRUE_VALUE.equals(lazyInit));
// 自动注入的方式,比如byName/byType
String autowire = ele.getAttribute(AUTOWIRE_ATTRIBUTE);
bd.setAutowireMode(getAutowireMode(autowire));
// 依赖bean depends-on元素设置的值
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 (isDefaultValue(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));
}
// primary元素
if (ele.hasAttribute(PRIMARY_ATTRIBUTE)) {
bd.setPrimary(TRUE_VALUE.equals(ele.getAttribute(PRIMARY_ATTRIBUTE)));
}
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);
}
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);
}
if (ele.hasAttribute(FACTORY_METHOD_ATTRIBUTE)) {
bd.setFactoryMethodName(ele.getAttribute(FACTORY_METHOD_ATTRIBUTE));
}
if (ele.hasAttribute(FACTORY_BEAN_ATTRIBUTE)) {
bd.setFactoryBeanName(ele.getAttribute(FACTORY_BEAN_ATTRIBUTE));
}
return bd;
}
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
将BeanDefinition注册到BeanDefinitionMap中。
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
String beanName = definitionHolder.getBeanName();
// 通过beanName注册BeanDefinition,其实就是注册到BeanDefinitionMap中
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);
}
}
}
@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);
}
}
// 判断BeanDefinitionMap中是否存在,如果存在就报错
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
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 {
// 如果BeanDefinitionMap中不存在,注册
// 判断bean是否开始创建,此时还没有开始创建,为false
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 {
// 注册到BeanDefinitionMap中
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}
至此,refresh方法中的obtainFreshBeanFactory()方法执行完成。
二、BeanFactory的前置准备,初始赋值
prepareBeanFactory(beanFactory);
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a bean.
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// Register early post-processor for detecting inner beans as ApplicationListeners.
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// Register default environment beans.
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
三、BeanFactory的后置处理
postProcessBeanFactory(beanFactory);
该方法默认没有实现,这里是留的扩展点,可以实现BeanFactoryPostProcessor去扩展。
四、执行BeanFactoryPostProcessor
invokeBeanFactoryPostProcessors(beanFactory);
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 执行ApplicationContext中的所有BeanFactoryProcessor
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
获取ApplicationContext中的BeanFactoryPostProcessor
public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
return this.beanFactoryPostProcessors;
}
五、注册BeanPostProcessor
registerBeanPostProcessors(beanFactory);
六、国际化
initMessageSource();
七、初始化事件监听多路广播器
initApplicationEventMulticaster();
八、onRefresh
这个方法是空的。解释是在特定的上下文中初始化特别的beans。可以看到其也是用于初始化的。
九、注册监听器
registerListeners();
十、实例化所有剩余的非懒加载单例 bean
finishBeanFactoryInitialization(beanFactory);
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
// 实例化所有非懒加载的单例bean
beanFactory.preInstantiateSingletons();
}
@Override
public void preInstantiateSingletons() throws BeansException {
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// 初始化所有非懒加载的单例bean
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
// 判断是否是FactoryBean
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
final FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
// 不是FactoryBean,注意这里走了获取Bean的过程
// 这里走getBean/doGetBean的过程,且里面走了getSingleton(beanName)的过程
// 这里不详细介绍,总而言之,这里创建了Bean
getBean(beanName);
}
}
}
for (String beanName : beanNames) {
// 重要,获取单例bean,这里使用了三级缓存
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
Object singletonInstance = getSingleton(beanName);这里是获取单例Bean,使用了三级缓存,解决Bean的循环依赖也是使用了三级缓存,循环依赖的问题后面再具体看,这里先看获取Bean。
DefaultSingletonBeanRegistry中有三个map分别对应三级缓存。
/** Cache of singleton objects: bean name to bean instance. 一级缓存 Bean初始化完成*/
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
/** Cache of early singleton objects: bean name to bean instance. 二级缓存 Bean未初始化完成*/
private final Map<String, Object> earlySingletonObjects = new HashMap<>(16);
/** Cache of singleton factories: bean name to ObjectFactory. 三级缓存 Bean还未初始化*/
private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);
再看获取单例Bean的逻辑
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
// 先从一级缓存中获取
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
// 如果一级缓存存没有,并且Bean是正在初始化的过程中(还未初始化完成)
synchronized (this.singletonObjects) {
// 再从二级缓存中获取
singletonObject = this.earlySingletonObjects.get(beanName);
if (singletonObject == null && allowEarlyReference) {
// 如果二级缓存中为空,allowEarlyReference这里为true
// 从三级缓存中获取,注意三级缓存中存放的是ObjectFactory,是创建bean的工厂
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
// 如果ObjectFactory不为null,创建对象,
// 这里getObject实际是执行的lambada表达式,lambada表达式是创建Bean的逻辑,后面可以再看
singletonObject = singletonFactory.getObject();
// 将创建的Bean放到二级缓存
this.earlySingletonObjects.put(beanName, singletonObject);
// 从三级缓存中删除,结合上面的put,可以看成是从三级缓存中升级到二级缓存
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;
}
十一、结束Refresh
finishRefresh();