Spring的IOC源码以及流程分析
zhāngpéngjūn 2022-04-02
源码分析
Java
IOC的流程分析，深入理解具体的接口和类，内容包括ApplicationContext，BeanDefinitionReader，BeanFactory,BeanFactoryPostProcessor,FactoryBean,BeanPostProcessor,Environment等。
- 一 前言
- 二 反射基础
- 三 设计模式
- 四 IOC流程分析
- 五 核心类分析
- 5.0 ContextLoaderListener与它的父类ContextLoader
- 5.1 classPathXmlApplicationContext
- 5.2 AbstractApplicationContext
- 5.3 prepareRefresh()
- 5.4 核心方法之一 obtainFreshBeanFactory()
- 5.5 prepareBeanFactory()
- 5.6 postProcessBeanFactory()
- 5.7 核心方法之一 invokeBeanFactoryPostProcessors()
- 5.8 核心方法之一 registerBeanPostProcessors()
- 5.9 initMessageSource()
- 5.10 initApplicationEventMulticaster()
- 5.11 onRefresh()
- 5.12 registerListeners()
- 5.13 核心方法之一 finishBeanFactoryInitialization(beanFactory)
- 5.14 finishRefresh()
- 总结
- 参考
# 一 前言
本文章的主要内容：
（1）反射，反射是框架设计的灵魂，必须会的。
（2）设计模式，框架里面体现了很多设计模式，比如单例模式，观察者模式，工厂模式等
（3）IOC的流程分析，spring源码之所以难，是因为里面的接口和类真的很多，可以将其中的核心接口和类了解清楚流程，并深入看一下其中的内容。想全部的掌握spring源码很难，并且没有那么大的必要，它已经封装好了，封装就是为了让你使用的。所以，我们只要把它的核心源码弄清楚就可以了。
（4）深入理解具体的接口和类，内容包括ApplicationContext，BeanDefinitionReader，BeanFactory,BeanFactoryPostProcessor,FactoryBean,BeanPostProcessor,Environment等。
# 二 反射基础
反射基础的话我为大家找了一篇清晰易懂的文章，这不是本文章的重点，请参考：
# 三 设计模式
设计模式的话，重点看其中的单例，观察者，工厂即可，参考：
# 四 IOC流程分析
# 4.1 IOC流程图
百度找的马士兵教育的流程图，侵删。
# 4.2 IOC流程图讲解
（1）从XML，配置类，annotation中读取响应的配置信息。
（2）如果想要对配置的信息进行人为的修改，可以采用BeanFactoryProcessor
（3）然后创建对应的BeanFactory，如果这个时候扩展的话，就可以利用FactoryBean，它是用来扩展的。
（4）实例化之前还可以利用BeanPostProcessor进行扩展
（5）利用反射进行实例化的过程。
（6）如果想要在容器的不同阶段做不同的事情，可以利用观察者模式，也就是监听器进行处理。
（7）其中的Environment也是一个重要的类，获取一些环境的属性。
先在脑海中有这样一张大概的流程图，然后再去看相应的源码部分抠细节。
# 五 核心类分析
以下类的内容都是双击shift查找得到的源码，由于源码过长，我真粘贴其中重要的部分进行分析。
# 5.0 ContextLoaderListener与它的父类ContextLoader
容器构建启动入口
容器构建启动的入口有多种多样，这边以常用的 web.xml 配置的方式来说。
首先，我们会在 web.xml 中配置 ContextLoaderListener 监听器，当 Tomcat 启动时，会触发 ContextLoaderListener 的 contextInitialized 方法，从而开始 IoC 的构建流程。
另一个常用的参数是 contextConfigLocation，用于指定 Spring 配置文件的路径。
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="Java EE: XML Schemas for Java EE Deployment Descriptors"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="Java EE: XML Schemas for Java EE Deployment Descriptors
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<display-name>open-joonwhee-service WAR</display-name>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
classpath*:config/spring/appcontext-*.xml
</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</web-app>
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ContextLoaderListener 是 Spring 的入口
并且的它的父类ContextLoader存在这样一个方法，可以实现扩功能先简单知道一下
refresh（）方法是核心，并且在它之前也需要做一些准备
请参考：https://blog.csdn.net/v123411739/article/details/86555733
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {
List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> initializerClasses =
determineContextInitializerClasses(sc);
for (Class<ApplicationContextInitializer<ConfigurableApplicationContext>> initializerClass : initializerClasses) {
Class<?> initializerContextClass =
GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class);
if (initializerContextClass != null && !initializerContextClass.isInstance(wac)) {
throw new ApplicationContextException(String.format(
"Could not apply context initializer [%s] since its generic parameter [%s] " +
"is not assignable from the type of application context used by this " +
"context loader: [%s]", initializerClass.getName(), initializerContextClass.getName(),
wac.getClass().getName()));
}
this.contextInitializers.add(BeanUtils.instantiateClass(initializerClass));
}
AnnotationAwareOrderComparator.sort(this.contextInitializers);
for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : this.contextInitializers) {
initializer.initialize(wac);
}
}
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# 5.1 classPathXmlApplicationContext
从这个类的注释我提取出了这样两句话
taking the context definition files from the class path
loading the definitions from the given XML files
意思就是从class path下提取全局的配置文件，加载给定的XML文件，也就知道了这个类大概就是加载一些配置的。
然后发现其中有两个构造方法中有refresh方法，那么这个refresh方法是干什么的呢？其实这是一个非常重要的方法，它将整个IOC的过程进行了一个串联，最关键的部分。
# 5.2 AbstractApplicationContext
上面提到了refresh方法，右键这个方法，goto，实现方法，就会到达这个重要的类，这是一个核心类，将所有的IOC过程进行了一个串联，那下面我们就对这个类的refresh方法进行一个详细的分析，依照四中给的图。然后我们将对其中的每一个方法进行具体的源码分析，深入每个方法之中。
其中最重要的几个方法：
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
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invokeBeanFactoryPostProcessors(beanFactory);
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registerBeanPostProcessors(beanFactory);
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finishBeanFactoryInitialization(beanFactory);
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然后我们将在后面的小结依次讲解各个方法。
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
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();
}
}
}
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# 5.3 prepareRefresh()
这个方法还是比较简单的，也就是做了一个时间戳，日志，环境校验，初始化监听器容器，初始化ApplicationEvents容器
protected void prepareRefresh() {
// Switch to active.
//前面这些就是记录以下启动的时间
this.startupDate = System.currentTimeMillis();
this.closed.set(false);
this.active.set(true);
//进行一些日志的设置
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
}
// Initialize any placeholder property sources in the context environment.
//这是一个空的方法，目前spring没有对其做任何事
initPropertySources();
// Validate that all properties marked as required are resolvable:
// see ConfigurablePropertyResolver#setRequiredProperties
//验证配置文件的有效性
//Environment这个类主要用于当前环境的判断，判断有效性之类的
//getEnvironment这个方法的逻辑你可以试着点进去，发现就是
//有的话直接返回，没有的话就创建一个
getEnvironment().validateRequiredProperties();
// Store pre-refresh ApplicationListeners...
//在最开始的图中我们也提到了监听器，这里就是监听器
//准备的时候创建一个监听器的容器
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// Reset local application listeners to pre-refresh state.
this.applicationListeners.clear();
this.applicationListeners.addAll(this.earlyApplicationListeners);
}
// Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
//在multicaster设置之前发布的ApplicationEvents
this.earlyApplicationEvents = new LinkedHashSet<>();
}
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# 5.4 核心方法之一 obtainFreshBeanFactory()
这个地方方法走的比较多，解释我基本都会写在注释当中
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
//一共有两步
//关闭旧的beanFactory 创建新的beanFactory 并注册
refreshBeanFactory();
//返回创造的对象
之后我们将具体来看一下这两个方法
return getBeanFactory();
}
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右键， refreshBeanFactory()，goto，来到相应的方法，这个方法在
AbstractRefreshableApplicationContext类当中
protected final void refreshBeanFactory() throws BeansException {
//这一步很简单，如果有的话，就关闭之前的，重新创建
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
//这一步又要详细分析这四个方法了
//这个方法里面就一句话
//new DefaultListableBeanFactory(getInternalParentBeanFactory());
//也就是创建一个beanFactory这个类，初步形成
DefaultListableBeanFactory beanFactory = createBeanFactory();
//设置序列化ID
beanFactory.setSerializationId(getId());
//这个地方有点意思，需要讲一下，在下面看一下它的方法
//customize是定制的意思，所以英文对程序员真的很有用
customizeBeanFactory(beanFactory);
//这是创建的时候最核心的方法，一层一层深入看一下吧
loadBeanDefinitions(beanFactory);
//设置到这个类的属性当中，用于返回对象方法时的使用
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
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customizeBeanFactory方法，定义覆盖以及循环依赖的问题
protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
if (this.allowBeanDefinitionOverriding != null) {
//是否允许bean定义的覆盖
// BeanDefinition 的覆盖问题大家也许会碰到，
// 就是在配置文件中定义 bean 时使用了相同的 id 或 name
// ，默认情况下，allowBeanDefinitionOverriding 属性为 null，
// 如果在同一配置文件中重复了，会抛错，但是如果不是同一配置文件中，会发生覆盖。
beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
if (this.allowCircularReferences != null) {
//是否允许bean 间的循环依赖
// A 依赖 B，而 B 依赖 A。或 A 依赖 B，B 依赖 C，而 C 依赖 A
// 默认情况下，Spring 允许循环依赖，当然如果你在 A 的构造方法中依赖 B，在 B 的构造方法中依赖 A 是不行的。
beanFactory.setAllowCircularReferences(this.allowCircularReferences);
}
}
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核心方法：loadBeanDefinitions(beanFactory)，这里就和我们图中的beanDefinitionReader联系在一起了，有内味儿了
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
// 创建同一个XmlBeanDefinitionReader 见名知意 xml的BeanDefine读取器转换器 也就是将xml文件转化为BeanDefinition
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
// 设置当前环境
beanDefinitionReader.setEnvironment(this.getEnvironment());
//这里的setResourceLoader赋值 我们在refresh方法的时候就已经给this赋值
//且看
// super(parent);
// // 将配置文件路径设置给AbstractRefreshableConfigApplicationContext 的 configLocations的属性
// setConfigLocations(configLocations); //这个方法就将配置路径赋值了
// // 由上面的参数传进refresh为true 下面我们就进入refresh方法 spring初始化全程
// if (refresh) {
// refresh();
// }
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);
//下面方法是核心
loadBeanDefinitions(beanDefinitionReader);
}
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继续进入loadBeanDefinitions(beanDefinitionReader);方法
点进reader.loadBeanDefinitions(configLocations);方法
点进loadBeanDefinitions方法
点进doLoadBeanDefinitions方法，在spring中带do的都是干实事的
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
//这里我们将资源文件转化为Document对象
Document doc = doLoadDocument(inputSource, resource);
//开始注册对应的BeanDefinition 我们继续进去
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);
}
}
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直接进入DefaultBeanDefinitionDocumentReader 下面的doRegisterBeanDefinitions
protected void doRegisterBeanDefinitions(Element root) {
// Any nested <beans> elements will cause recursion in this method. In
// rder 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);
// 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);
// 解析xml 将xml元素转化为BeanDefinition
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);
this.delegate = parent;
}
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根据上面的解释我们直接进入parseBeanDefinitions(root, this.delegate);
再进入parseDefaultElement(ele, delegate)
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
//处理import标签
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
//处理alias标签
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
//处理bean标签
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// 处理beans标签
doRegisterBeanDefinitions(ele);
}
}
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进入processBeanDefinition(ele, delegate);我们只关心bean
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
// xml节点信息转化为BeanDefinitionHolder对象
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
//如果有自定义属性的话 进行相应的解析
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
// 这一步就是注册bean啦
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));
}
}
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进入registerBeanDefinition方法
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
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);
}
}
}
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再进入registry.registerBeanDefinition
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);
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 {
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)) {
resetBeanDefinition(beanName);
}
}
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然后我们看看这个DefaultListableBeanFactory的关系图
到此为止基本就创建完了，最后执行获取这个操作了。
public final ConfigurableListableBeanFactory getBeanFactory() {
//因为在刚才的refreshBeanFactory()方法中，我们已经将beanFactory这个类设置到this当中了
//所以在这个地方直接获取
synchronized (this.beanFactoryMonitor) {
if (this.beanFactory == null) {
throw new IllegalStateException("BeanFactory not initialized or already closed - " +
"call 'refresh' before accessing beans via the ApplicationContext");
}
return this.beanFactory;
}
}
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# 5.5 prepareBeanFactory()
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
//设置类加载器：存在则直接设置/不存在则新建一个默认类加载器
beanFactory.setBeanClassLoader(getClassLoader());
//设置EL表达式解析器（Bean初始化完成后填充属性时会用到）
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
//设置属性注册解析器PropertyEditor
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// 将当前的ApplicationContext对象交给ApplicationContextAwareProcessor类来处理，从而在Aware接口实现类中的注入applicationContext
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
//设置忽略自动装配的接口
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
//注册可以解析的自动装配
// 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);
//如果当前BeanFactory包含loadTimeWeaver Bean，说明存在类加载期织入AspectJ，则把当前BeanFactory交给类加载期BeanPostProcessor实现类LoadTimeWeaverAwareProcessor来处理，从而实现类加载期织入AspectJ的目的。
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()));
}
//注册当前容器环境environment组件Bean
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
//注册系统配置systemProperties组件Bean
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
//注册系统环境systemEnvironment组件Bean
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
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# 5.6 postProcessBeanFactory()
spring中并没有具体去实现postProcessBeanFactory方法，作用是在BeanFactory准备工作完成后做一些定制化的处理。
# 5.7 核心方法之一 invokeBeanFactoryPostProcessors()
Instantiate and invoke all registered BeanFactoryPostProcessor beans,respecting explicit order if given.
上面是对这个方法的描述，调用所有注册的BeanFactoryPostProcessor，并遵循显式顺序（如果给定的话）。
BeanFactoryPostProcessor 接口是 Spring 初始化 BeanFactory 时对外暴露的扩展点，Spring IoC 容器允许 BeanFactoryPostProcessor 在容器实例化任何 bean 之前读取 bean 的定义，并可以修改它。
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
//getBeanFactoryPostProcessors(): 拿到当前应用上下文beanFactoryPostProcessors变量中的值
//invokeBeanFactoryPostProcessors: 实例化并调用所有已注册的BeanFactoryPostProcessor
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
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这一段代码的核心在于获取和调用，下面进行详细的讲解 getBeanFactoryPostProcessors()，这个方法默认是没有的，返回null
public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
return this.beanFactoryPostProcessors;
}
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如何添加自定义 BeanFactoryPostProcessor 到 this.beanFactoryPostProcessors 变量中了？
新建一个 ApplicationContextInitializer 的实现类 SpringApplicationContextInitializer ，并在 initialize 方法中写我们的逻辑。
package com.joonwhee.open.demo.spring;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
/**
* @author joonwhee
* @date 2019/1/19
*/
public class SpringApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
FirstBeanDefinitionRegistryPostProcessor firstBeanDefinitionRegistryPostProcessor = new FirstBeanDefinitionRegistryPostProcessor();
// 将自定义的firstBeanDefinitionRegistryPostProcessor添加到应用上下文中
applicationContext.addBeanFactoryPostProcessor(firstBeanDefinitionRegistryPostProcessor);
// ...自定义操作
System.out.println("SpringApplicationContextInitializer#initialize");
}
}
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将 SpringApplicationContextInitializer 作为初始化参数 contextInitializerClasses 配置到 web.xml 中。
<context-param>
<param-name>contextInitializerClasses</param-name>
<param-value>
com.joonwhee.open.demo.spring.SpringApplicationContextInitializer
</param-value>
</context-param>
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invokeBeanFactoryPostProcessors方法
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<String>();
// 1.判断beanFactory是否为BeanDefinitionRegistry，beanFactory为DefaultListableBeanFactory,
// 而DefaultListableBeanFactory实现了BeanDefinitionRegistry接口，因此这边为true
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// 用于存放普通的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
// 用于存放BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
// 2.首先处理入参中的beanFactoryPostProcessors
// 遍历所有的beanFactoryPostProcessors, 将BeanDefinitionRegistryPostProcessor和普通BeanFactoryPostProcessor区分开
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
// 2.1 如果是BeanDefinitionRegistryPostProcessor
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// 2.1.1 直接执行BeanDefinitionRegistryPostProcessor接口的postProcessBeanDefinitionRegistry方法
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// 2.1.2 添加到registryProcessors(用于最后执行postProcessBeanFactory方法)
registryProcessors.add(registryProcessor);
} else {
// 2.2 否则，只是普通的BeanFactoryPostProcessor
// 2.2.1 添加到regularPostProcessors(用于最后执行postProcessBeanFactory方法)
regularPostProcessors.add(postProcessor);
}
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
// 用于保存本次要执行的BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 3.调用所有实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor实现类
// 3.1 找出所有实现BeanDefinitionRegistryPostProcessor接口的Bean的beanName
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
// 3.2 遍历postProcessorNames
for (String ppName : postProcessorNames) {
// 3.3 校验是否实现了PriorityOrdered接口
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 3.4 获取ppName对应的bean实例, 添加到currentRegistryProcessors中,
// beanFactory.getBean: 这边getBean方法会触发创建ppName对应的bean对象, 目前暂不深入解析
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
// 3.5 将要被执行的加入processedBeans，避免后续重复执行
processedBeans.add(ppName);
}
}
// 3.6 进行排序(根据是否实现PriorityOrdered、Ordered接口和order值来排序)
sortPostProcessors(currentRegistryProcessors, beanFactory);
// 3.7 添加到registryProcessors(用于最后执行postProcessBeanFactory方法)
registryProcessors.addAll(currentRegistryProcessors);
// 3.8 遍历currentRegistryProcessors, 执行postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// 3.9 执行完毕后, 清空currentRegistryProcessors
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// 4.调用所有实现了Ordered接口的BeanDefinitionRegistryPostProcessor实现类（过程跟上面的步骤3基本一样）
// 4.1 找出所有实现BeanDefinitionRegistryPostProcessor接口的类, 这边重复查找是因为执行完上面的BeanDefinitionRegistryPostProcessor,
// 可能会新增了其他的BeanDefinitionRegistryPostProcessor, 因此需要重新查找
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 校验是否实现了Ordered接口，并且还未执行过
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 4.2 遍历currentRegistryProcessors, 执行postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// 5.最后, 调用所有剩下的BeanDefinitionRegistryPostProcessors
boolean reiterate = true;
while (reiterate) {
reiterate = false;
// 5.1 找出所有实现BeanDefinitionRegistryPostProcessor接口的类
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 5.2 跳过已经执行过的
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
// 5.3 如果有BeanDefinitionRegistryPostProcessor被执行, 则有可能会产生新的BeanDefinitionRegistryPostProcessor,
// 因此这边将reiterate赋值为true, 代表需要再循环查找一次
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 5.4 遍历currentRegistryProcessors, 执行postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 6.调用所有BeanDefinitionRegistryPostProcessor的postProcessBeanFactory方法(BeanDefinitionRegistryPostProcessor继承自BeanFactoryPostProcessor)
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// 7.最后, 调用入参beanFactoryPostProcessors中的普通BeanFactoryPostProcessor的postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
} else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// 到这里 , 入参beanFactoryPostProcessors和容器中的所有BeanDefinitionRegistryPostProcessor已经全部处理完毕,
// 下面开始处理容器中的所有BeanFactoryPostProcessor
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// 8.找出所有实现BeanFactoryPostProcessor接口的类
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 用于存放实现了PriorityOrdered接口的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
// 用于存放实现了Ordered接口的BeanFactoryPostProcessor的beanName
List<String> orderedPostProcessorNames = new ArrayList<String>();
// 用于存放普通BeanFactoryPostProcessor的beanName
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
// 8.1 遍历postProcessorNames, 将BeanFactoryPostProcessor按实现PriorityOrdered、实现Ordered接口、普通三种区分开
for (String ppName : postProcessorNames) {
// 8.2 跳过已经执行过的
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
} else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 8.3 添加实现了PriorityOrdered接口的BeanFactoryPostProcessor
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
} else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
// 8.4 添加实现了Ordered接口的BeanFactoryPostProcessor的beanName
orderedPostProcessorNames.add(ppName);
} else {
// 8.5 添加剩下的普通BeanFactoryPostProcessor的beanName
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
// 9.调用所有实现PriorityOrdered接口的BeanFactoryPostProcessor
// 9.1 对priorityOrderedPostProcessors排序
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
// 9.2 遍历priorityOrderedPostProcessors, 执行postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
// 10.调用所有实现Ordered接口的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : orderedPostProcessorNames) {
// 10.1 获取postProcessorName对应的bean实例, 添加到orderedPostProcessors, 准备执行
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
// 10.2 对orderedPostProcessors排序
sortPostProcessors(orderedPostProcessors, beanFactory);
// 10.3 遍历orderedPostProcessors, 执行postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
// 11.调用所有剩下的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
// 11.1 获取postProcessorName对应的bean实例, 添加到nonOrderedPostProcessors, 准备执行
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
// 11.2 遍历nonOrderedPostProcessors, 执行postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
// 12.清除元数据缓存（mergedBeanDefinitions、allBeanNamesByType、singletonBeanNamesByType），
// 因为后处理器可能已经修改了原始元数据，例如， 替换值中的占位符...
beanFactory.clearMetadataCache();
}
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# 5.8 核心方法之一 registerBeanPostProcessors()
本方法会注册所有的 BeanPostProcessor，将所有实现了 BeanPostProcessor 接口的类加载到 BeanFactory 中。BeanPostProcessor 接口是 Spring 初始化 bean 时对外暴露的扩展点，Spring IoC 容器允许 BeanPostProcessor 在容器初始化 bean 的前后，添加自己的逻辑处理。
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 1.找出所有实现BeanPostProcessor接口的类
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
// BeanPostProcessor的目标计数
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
// 2.添加BeanPostProcessorChecker(主要用于记录信息)到beanFactory中
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 3.定义不同的变量用于区分: 实现PriorityOrdered接口的BeanPostProcessor、实现Ordered接口的BeanPostProcessor、普通BeanPostProcessor
// 3.1 priorityOrderedPostProcessors: 用于存放实现PriorityOrdered接口的BeanPostProcessor
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
// 3.2 internalPostProcessors: 用于存放Spring内部的BeanPostProcessor
List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
// 3.3 orderedPostProcessorNames: 用于存放实现Ordered接口的BeanPostProcessor的beanName
List<String> orderedPostProcessorNames = new ArrayList<String>();
// 3.4 nonOrderedPostProcessorNames: 用于存放普通BeanPostProcessor的beanName
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
// 4.遍历postProcessorNames, 将BeanPostProcessors按3.1 - 3.4定义的变量区分开
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 4.1 如果ppName对应的Bean实例实现了PriorityOrdered接口, 则拿到ppName对应的Bean实例并添加到priorityOrderedPostProcessors
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
// 4.2 如果ppName对应的Bean实例也实现了MergedBeanDefinitionPostProcessor接口,
// 则将ppName对应的Bean实例添加到internalPostProcessors
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
// 4.3 如果ppName对应的Bean实例没有实现PriorityOrdered接口, 但是实现了Ordered接口, 则将ppName添加到orderedPostProcessorNames
orderedPostProcessorNames.add(ppName);
}
else {
// 4.4 否则, 将ppName添加到nonOrderedPostProcessorNames
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
// 5.首先, 注册实现PriorityOrdered接口的BeanPostProcessors
// 5.1 对priorityOrderedPostProcessors进行排序
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
// 5.2 注册priorityOrderedPostProcessors
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
// 6.接下来, 注册实现Ordered接口的BeanPostProcessors
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : orderedPostProcessorNames) {
// 6.1 拿到ppName对应的BeanPostProcessor实例对象
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
// 6.2 将ppName对应的BeanPostProcessor实例对象添加到orderedPostProcessors, 准备执行注册
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
// 6.3 如果ppName对应的Bean实例也实现了MergedBeanDefinitionPostProcessor接口,
// 则将ppName对应的Bean实例添加到internalPostProcessors
internalPostProcessors.add(pp);
}
}
// 6.4 对orderedPostProcessors进行排序
sortPostProcessors(orderedPostProcessors, beanFactory);
// 6.5 注册orderedPostProcessors
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
// 7.注册所有常规的BeanPostProcessors（过程与6类似）
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
// 8.最后, 重新注册所有内部BeanPostProcessors（相当于内部的BeanPostProcessor会被移到处理器链的末尾）
// 8.1 对internalPostProcessors进行排序
sortPostProcessors(internalPostProcessors, beanFactory);
// 8.2注册internalPostProcessors
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
// 9.重新注册ApplicationListenerDetector（跟8类似，主要是为了移动到处理器链的末尾）
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
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使用：可以在bean的初始化前后添加自己想要的代码
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 1.找出所有实现BeanPostProcessor接口的类
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
// BeanPostProcessor的目标计数
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
// 2.添加BeanPostProcessorChecker(主要用于记录信息)到beanFactory中
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 3.定义不同的变量用于区分: 实现PriorityOrdered接口的BeanPostProcessor、实现Ordered接口的BeanPostProcessor、普通BeanPostProcessor
// 3.1 priorityOrderedPostProcessors: 用于存放实现PriorityOrdered接口的BeanPostProcessor
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
// 3.2 internalPostProcessors: 用于存放Spring内部的BeanPostProcessor
List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
// 3.3 orderedPostProcessorNames: 用于存放实现Ordered接口的BeanPostProcessor的beanName
List<String> orderedPostProcessorNames = new ArrayList<String>();
// 3.4 nonOrderedPostProcessorNames: 用于存放普通BeanPostProcessor的beanName
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
// 4.遍历postProcessorNames, 将BeanPostProcessors按3.1 - 3.4定义的变量区分开
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 4.1 如果ppName对应的Bean实例实现了PriorityOrdered接口, 则拿到ppName对应的Bean实例并添加到priorityOrderedPostProcessors
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
// 4.2 如果ppName对应的Bean实例也实现了MergedBeanDefinitionPostProcessor接口,
// 则将ppName对应的Bean实例添加到internalPostProcessors
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
// 4.3 如果ppName对应的Bean实例没有实现PriorityOrdered接口, 但是实现了Ordered接口, 则将ppName添加到orderedPostProcessorNames
orderedPostProcessorNames.add(ppName);
}
else {
// 4.4 否则, 将ppName添加到nonOrderedPostProcessorNames
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
// 5.首先, 注册实现PriorityOrdered接口的BeanPostProcessors
// 5.1 对priorityOrderedPostProcessors进行排序
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
// 5.2 注册priorityOrderedPostProcessors
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
// 6.接下来, 注册实现Ordered接口的BeanPostProcessors
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : orderedPostProcessorNames) {
// 6.1 拿到ppName对应的BeanPostProcessor实例对象
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
// 6.2 将ppName对应的BeanPostProcessor实例对象添加到orderedPostProcessors, 准备执行注册
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
// 6.3 如果ppName对应的Bean实例也实现了MergedBeanDefinitionPostProcessor接口,
// 则将ppName对应的Bean实例添加到internalPostProcessors
internalPostProcessors.add(pp);
}
}
// 6.4 对orderedPostProcessors进行排序
sortPostProcessors(orderedPostProcessors, beanFactory);
// 6.5 注册orderedPostProcessors
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
// 7.注册所有常规的BeanPostProcessors（过程与6类似）
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
// 8.最后, 重新注册所有内部BeanPostProcessors（相当于内部的BeanPostProcessor会被移到处理器链的末尾）
// 8.1 对internalPostProcessors进行排序
sortPostProcessors(internalPostProcessors, beanFactory);
// 8.2注册internalPostProcessors
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
// 9.重新注册ApplicationListenerDetector（跟8类似，主要是为了移动到处理器链的末尾）
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
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# 5.9 initMessageSource()
/**
* Initialize the MessageSource.
* Use parent's if none defined in this context.
*/
protected void initMessageSource() {
//获取Bean工厂，一般是DefaultListBeanFactory
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
//首先判断是否已有xml文件定义了id为messageSource的bean对象
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
//如果有，则从Bean工厂得到这个bean对象
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
// Make MessageSource aware of parent MessageSource.
//当父类Bean工厂不为空，并且这个bean对象是HierarchicalMessageSource类型
if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
//为HierarchicalMessageSource的实现类
HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
//设置父类MessageSource，此处设置内部的parent messageSource
if (hms.getParentMessageSource() == null) {
// Only set parent context as parent MessageSource if no parent MessageSource
// registered already.
hms.setParentMessageSource(getInternalParentMessageSource());
}
}
if (logger.isTraceEnabled()) {
logger.trace("Using MessageSource [" + this.messageSource + "]");
}
}
else {
// Use empty MessageSource to be able to accept getMessage calls.
//如果没有xml文件定义信息源对象，新建DelegatingMessageSource类作为messageSource的Bean
//因为DelegatingMessageSource类实现了HierarchicalMessageSource接口，而这个接口继承了MessageSource这个类
//因此实现了这个接口的类，都是MessageSource的子类，因此DelegatingMessageSource也是一个MessageSource
DelegatingMessageSource dms = new DelegatingMessageSource();
//给这个DelegatingMessageSource添加父类消息源
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
//将这个messageSource实例注册到Bean工厂中
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isTraceEnabled()) {
logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
}
}
}
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# 5.10 initApplicationEventMulticaster()
代码很简单，就是分两种情况进行初始化的过程
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isTraceEnabled()) {
logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
if (logger.isTraceEnabled()) {
logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
}
}
}
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# 5.11 onRefresh()
这个方法是空的没有进行实现，官网给的注释是
Initialize other special beans in specific context subclasses.
初始化一些其他的特殊的bean
# 5.12 registerListeners()
获取ApplicationContext初始化的listeners，然后添加到EventMulticaster，这个刚才初始化的
这里面的earlyApplicationEvents是在第一步的时候进行初始化的
在prepareRefresh方法中的
this.earlyApplicationEvents = new LinkedHashSet<>();
protected void registerListeners() {
// Register statically specified listeners first.
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let post-processors apply to them!
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// Publish early application events now that we finally have a multicaster...
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
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自定义监听器的实现
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;
@Component
public class MyRefreshedListener implements ApplicationListener<ContextRefreshedEvent> {
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
// 自己的逻辑处理
}
}
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# 5.13 核心方法之一 finishBeanFactoryInitialization(beanFactory)
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
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));
}
// Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
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();
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
}
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关键起作用的在最后一行beanFactory.preInstantiateSingletons();我们进入
这个时候发现又进入了我们的老朋友
DefaultListableBeanFactory这个重要的类
这里里面的关键代码在于通过名字获取bean，也就是getBean(beanName);方法
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) {
logger.trace("Pre-instantiating singletons in " + this);
}
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
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 {
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
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();
}
}
}
}
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我们进入getBean(beanName);方法
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
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发现仅仅是调用了dogetbean这个方法，但是我们在这里看到了do，在spring中do都是干实事的地方，那我们就要知道，创建bean的重点来了。
protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
//这部分是通过getSingleton(beanName)方法去singleton缓存中找bean实例，
//应该是拿不到的，因为我们是第一次初始化，缓存中肯定不存在。
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isTraceEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
//这段是根据当前的beanfactory获取父一级的beanfactory，然后逐级递归的查找我们需要的bean
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
//第三部分先判断并把需要创建的bean打上正在创建标记，
//也就是开头的if判断加markBeanAsCreated(beanName)方法
//（这样做的目的是在我创建这个bean之前就先打上创建标记，告诉其它来创建的线程，避免了重复创建，那么这个方法内部肯定是同步的）
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
return convertedBean;
}
catch (TypeMismatchException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
不知道小伙伴能否在这里体会到反射的思想呢
# 5.14 finishRefresh()
最后进行一些收尾工作
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
clearResourceCaches();
// Initialize lifecycle processor for this context.
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh();
// Publish the final event.
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
# 总结
# 源码分析中比较重要的类有
ApplicationContet（主要的容器，串联流程）
Environment（可以判断环境的有效性）
BeanPostProcessor（用于bean实例化前后的扩展）
BeanFactory（最顶层的一个接口）
FactoryBean（也是用来更好的扩展，他也就有三个方法）
BeanFactoryPostPorcessor（用来工厂后来的扩展）
BeanDefinitionReader（读取前面的一些信息）
classPathXmlApplicationContext（读取总的配置文件）
ContextLoaderListener与它的父类ContextLoader（spring的入口）
# 参考
1.https://blog.csdn.net/spring_live_in/article/details/101059038
2.https://blog.csdn.net/sinat_38259539/article/details/71799078?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-4&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-4
3.https://liteyu.blog.csdn.net/article/details/105754312
4.https://blog.csdn.net/v123411739/article/details/87741251