最后更新于：2018-08-26
Spring(一) IOC核心类
Spring(二) Resource定位与载入
Spring(三) BeanDefinition解析与注册
Spring(四) 自定义标签解析
Spring(五) 其他初始化步骤
Spring(六) bean的加载01
Spring(七) bean的加载02
Spring(八) SpringBean的生命周期
Spring(九) IOC时序图
Spring(十) AOP 01
Spring(十一) AOP 02
Spring(十二) spring事务
准备
spring版本：5.0.8.RELEASE，将源码切换git checkout v5.0.8.RELEASE
System.out.println("--------------【初始化容器】---------------");
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext1.xml");
System.out.println("-------------------【容器初始化成功】------------------");
Person p = (Person) applicationContext.getBean("jack"); // getPerson
System.out.println(p.getMoney().getAmount());
System.out.println("--------------------【销毁容器】----------------------");
((ClassPathXmlApplicationContext)applicationContext).registerShutdownHook();
源码跟踪
1 . 创建ClassPathXmlApplicationContext，调用构造函数
// 一直往上调用到父类AbstractApplicationContext构造方法，初始化属性，并为容器设置好bean资源加载器ResourceLoader
super(parent);
// 设置bean定义资源文件的定位路径
this.setConfigLocations(configLocations);
if(refresh) {
// 初始化入口
this.refresh();
}
ps.对于AnnotationConfigApplicationContext来说有点不同
public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
// 设置reader与scanner：AnnotatedBeanDefinitionReader、ClassPathBeanDefinitionScanner
// 创建AnnotatedBeanDefinitionReader时里面会调用registerAnnotationConfigProcessors，里面注册了多个Processor Definition
this();
// 注册传入的annotatedClasses：@Configuration
register(annotatedClasses);
// 一样，因为继承GenericApplicationContext而不是AbstractXmlApplicationContext，所以部分模板方法调用父类的实现不同
// beanDefinition的注册不在obtainFreshBeanFactory中进行，而是在invokeBeanFactoryPostProcessors中通过
// invokeBeanDefinitionRegistryPostProcessors方法里的ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry去查找注册
refresh();
}
2 . 调用父类AbstractApplicationContext的refresh方法，是比较核心的方法，Spring所有的初始化都在这个方法中完成
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
// a.准备工作：设置spring启动时间，是否结束/激活标识；初始化属性源(默认空方法，留给子类覆盖)；验证必要属性
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
// b.创建beanFactory，如果已有就销毁后创建，这里就是实现BeanFactory全部功能的地方，
// 过程是对BeanDefinition的装载: 根据xml为每个bean生成BeanDefinition并注册到生成的beanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
// 配置创建好的beanFactory的标准上下文配置
// 给beanFactory设置ClassLoader，设置SpEL表达式解析器，设置类型转化器[能将xml String类型转成相应对象]，
// 增加内置ApplicationContextAwareProcessor对象，忽略各种Aware对象，注册各种内置的对账对象[BeanFactory，ApplicationContext]等，
// 注册环境相关的一些系统属性等
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
// 模板方法，提供一个修改容器的beanFactory的入口，子类特殊的bean factory设置，默认为空实现
// 比如GenericWebApplicationContext容器会在BeanFactory中添加ServletContextAwareProcessor。
// 用于处理ServletContextAware类型的bean，初始化的时候调用setServletContext或者setServletConfig方法
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
// 从Spring容器中找出BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor接口的实现类，实例化并按照一定的规则顺序进行执行postProcessBeanFactory方法
// (在用AnnotationConfigApplicationContext时会register这个)比如ConfigurationClassPostProcessor(实现了PriorityOrdered接口)，会去BeanFactory中找出所有有@Configuration注解的bean，然后使用ConfigurationClassParser去解析这个类，解析完成之后把这些bean注册到BeanFactory中。需要注意的是这个时候注册进来的bean还没有实例化
// 其内部有个Map类型的configurationClasses属性用于保存解析的类，ConfigurationClass是一个对要解析的配置类的封装，内部存储了配置类的注解信息、被@Bean注解修饰的方法、@ImportResource注解修饰的信息、ImportBeanDefinitionRegistrar等都存储在这个封装类中(@Component、@ComponentScan、@Import、@ImportResource修饰的类)
// 比如PropertyPlaceholderConfigurer，用来解析${...}占位符
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
// 注册用于拦截bean创建过程的BeanPostProcessor
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
// 实例化，注册和设置国际化工具类MessageSource
initMessageSource();
// Initialize event multicaster for this context.
// 实例化，注册和设置事件广播类，用于发布事件(如果没有自己定义使用默认的SimpleApplicationEventMulticaster实现，此广播使用同步的通知方式)
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
// 模板方法，调用子类特殊的刷新逻辑，不同容器各自实现，默认为空方法
onRefresh();
// Check for listener beans and register them.
// 为事件传播器注册事件监听器，添加ApplicationListener实现类到上面设置的消息广播ApplicationEventMulticaster
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
// 完成容器的初始化，实例化BeanFactory中已经被注册但是没被实例化的所有单例(懒加载除外)
// 设置自定义的类型转化器ConversionService，设置自定义AOP相关的类LoadTimeWeaverAware，清除临时的ClassLoader，冻结配置
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
// 初始化容器的生命周期事件处理器，并发布容器的生命周期事件
// 初始化生命周期处理器LifecycleProcessor(默认使用DefaultLifecycleProcessor)并调用其onrefresh方法，找到SmartLifecycle接口的所有实现类并调用start方法
// 发布事件告知listener，如果设置了JMX相关属性，还会调用LiveBeansView的registerApplicationContext方法
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();
}
}
}
2-b-1 . 获取新的BeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = this.getBeanFactory();
if(this.logger.isDebugEnabled()) {
this.logger.debug("Bean factory for " + this.getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
2-b-2 . 执行AbstractRefreshableApplicationContext的refreshBeanFactory方法，获得新的BeanFactory
protected final void refreshBeanFactory() throws BeansException {
// 如果已有BeanFactory，则销毁beans，并且关闭BeanFactory
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
// 设置是否允许同名bean覆盖，设置是否允许循环引用
customizeBeanFactory(beanFactory);
// 加载BeanDefinitions
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
} catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
2-b-3 . 进入AbstractXmlApplicationContext加载BeanDefinitions
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// 创建一个XmlBeanDefinitionReader，将beanFactory作为BeanDefinitionRegistry记录
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// 配置资源加载环境
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// 初始化(可定义子类执行自定义初始化): 默认设置允许XML validation
initBeanDefinitionReader(beanDefinitionReader);
// 加载BeanDefinitions
loadBeanDefinitions(beanDefinitionReader);
}
2-b-4 . 获取Resource资源或者路径，使用XmlBeanDefinitionReader加载BeanDefinitions，实际调用父类AbstractBeanDefinitionReader的loadBeanDefinitions方法。
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
// 获取ResourceLoader: 这里是ClassPathXmlApplicationContext
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
}
// ApplicationContext是继承了ResourcePatternResolver
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
// AbstractApplicationContext(构造函数设置的).PathMatchingResourcePatternResolver.getResources
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
int loadCount = loadBeanDefinitions(resources);
if (actualResources != null) {
for (Resource resource : resources) {
actualResources.add(resource);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
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;
}
}
2-b-5 . 调用XmlBeanDefinitionReader的loadBeanDefinitions方法
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
// 将resource封装成EncodedResource
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());
}
// 来记录已经加载过的资源，解决资源文件重复引用的问题: ThreadLocal<Set<EncodedResource>>
Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
// 添加新资源到set，如果已经存在则抛出异常，处理循环加载exception
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
// 从encodedResource获取封装的resource对象，获取其中的inputStream(java.io.BufferedInputStream)
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
// org.xml.sax.InputSource，通过SAX读取
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// 真正进入核心逻辑
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
finally {
inputStream.close(); // 关闭输入流
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
2-b-6 . 将bean定义资源转换为Document对象，然后解析并注册BeanDefinitions
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
Document doc = doLoadDocument(inputSource, resource);
return registerBeanDefinitions(doc, resource);
}
catch ...
}
2-b-7 . 委托给DefaultDocumentLoader加载并校验
protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
// SAX解析XML，需要读取XML文档上的声明，EntityResolver可以提供获取声明的方法，可避免通过网络来寻找相应声明，这里SXD类型通过META-INF/spring.schemas文件找到systemid对应XSD文件加载
return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
// 验证模式的读取，有指定用指定，否则使用自动检测验证模式委托给XmlValidationModeDetector处理: DTD or XSD
getValidationModeForResource(resource), isNamespaceAware());
}
public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {
DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
if (logger.isDebugEnabled()) {
logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");
}
DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
return builder.parse(inputSource);
}
2-b-8 . 解析并注册BeanDefinitions，调用XmlBeanDefinitionReader.registerBeanDefinitions方法
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
// 使用DefaultBeanDefinitionDocumentReader
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
// 统计之前BeanDefinition的加载个数
// getRegistry() => ClassPathXmlApplicationContext，在2-b-3中放入的
int countBefore = getRegistry().getBeanDefinitionCount();
// 加载与注册BeanDefinitions
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
// 统计本次BeanDefinition的加载个数
return getRegistry().getBeanDefinitionCount() - countBefore;
}
2-b-9 . 提取root，将root作为参数继续BeanDefinitions注册
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
doRegisterBeanDefinitions(root);
}
2-b-10 . DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions真正开始解析了
protected void doRegisterBeanDefinitions(Element root) {
// Any nested(嵌套的) <beans> elements will cause recursion(递归) in this method.
// In order to propagate(传播) and preserve(保存) <beans> default-* attributes correctly,
// keep track of the current (parent) delegate(委托), which may be null.
// Create the new (child) delegate with a reference to the parent for fallback purposes(作用), then ultimately(最终) reset this.
// delegate back to its original (parent) reference.
// this behavior emulates a stack of delegates without actually necessitating(必要) one.
// BeanDefinitionParserDelegate中定义了Spring Bean定义在XML文件的各种元素
BeanDefinitionParserDelegate parent = this.delegate;
// 创建BeanDefinitionParserDelegate，用于完成真正的解析过程，负责解析xml element，生成beanDenition并放入到BeanDefinitionHolder当中
this.delegate = createDelegate(getReaderContext(), root, parent);
if (this.delegate.isDefaultNamespace(root)) {
// 处理profile属性: 先获取bean节点看是否定义了profile属性，如果定义了则需要到环境变量中寻找。这里断言environment不可能为空，因为profile可以同时指定多个，需要将其拆分。并解析每个profile是否符合环境变量中所定义的，不定义则不去解析
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;
}
}
}
// 空方法，又没有用final修饰，所以是面向继承而设计的，这里利用了模版方法模式
// 前处理，默认空实现，留给子类扩展
preProcessXml(root);
// 核心，解析并注册
parseBeanDefinitions(root, this.delegate);
// 后处理，默认空实现，留给子类扩展
postProcessXml(root);
this.delegate = parent; // reset this
}
2-b-11 . 根据父delegate创建一个BeanDefinitionParserDelegate对象
protected BeanDefinitionParserDelegate createDelegate(
XmlReaderContext readerContext, Element root, @Nullable BeanDefinitionParserDelegate parentDelegate) {
BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext);
delegate.initDefaults(root, parentDelegate);
return delegate;
}
public void initDefaults(Element root, @Nullable BeanDefinitionParserDelegate parent) {
populateDefaults(this.defaults, (parent != null ? parent.defaults : null), root);
this.readerContext.fireDefaultsRegistered(this.defaults);
}
// 进行标签属性值的设置
protected void populateDefaults(DocumentDefaultsDefinition defaults, @Nullable DocumentDefaultsDefinition parentDefaults, Element root) {
String lazyInit = root.getAttribute(DEFAULT_LAZY_INIT_ATTRIBUTE); // default-lazy-init
if (DEFAULT_VALUE.equals(lazyInit)) {
// Potentially inherited from outer <beans> sections, otherwise falling back to false.
lazyInit = (parentDefaults != null ? parentDefaults.getLazyInit() : FALSE_VALUE);
}
defaults.setLazyInit(lazyInit);
String merge = root.getAttribute(DEFAULT_MERGE_ATTRIBUTE); // default-merge
if (DEFAULT_VALUE.equals(merge)) {
// Potentially inherited from outer <beans> sections, otherwise falling back to false.
merge = (parentDefaults != null ? parentDefaults.getMerge() : FALSE_VALUE);
}
defaults.setMerge(merge);
String autowire = root.getAttribute(DEFAULT_AUTOWIRE_ATTRIBUTE); // default-autowire
if (DEFAULT_VALUE.equals(autowire)) {
// Potentially inherited from outer <beans> sections, otherwise falling back to 'no'.
autowire = (parentDefaults != null ? parentDefaults.getAutowire() : AUTOWIRE_NO_VALUE);
}
defaults.setAutowire(autowire);
if (root.hasAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE)) { // default-autowire-candidates
defaults.setAutowireCandidates(root.getAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE));
}
else if (parentDefaults != null) {
defaults.setAutowireCandidates(parentDefaults.getAutowireCandidates());
}
if (root.hasAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE)) { // default-init-method
defaults.setInitMethod(root.getAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE));
}
else if (parentDefaults != null) {
defaults.setInitMethod(parentDefaults.getInitMethod());
}
if (root.hasAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE)) { // default-destroy-method
defaults.setDestroyMethod(root.getAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE));
}
else if (parentDefaults != null) {
defaults.setDestroyMethod(parentDefaults.getDestroyMethod());
}
defaults.setSource(this.readerContext.extractSource(root));
}
public void fireDefaultsRegistered(DefaultsDefinition defaultsDefinition) {
this.eventListener.defaultsRegistered(defaultsDefinition);
}
2-b-12 . 进行XML的读取
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
// 对beans处理，默认的namespace
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)) {
// a.对默认的元素标签处理，如<bean/> <alias/> <import/>
parseDefaultElement(ele, delegate);
}
else {
// b.对自定义元素标签处理，<tx:annotation-driven/>
delegate.parseCustomElement(ele);
}
}
}
}
else {
// b.对自定义元素标签处理
delegate.parseCustomElement(root);
}
}