先从源码来看 spring 的 IOC 都经历了哪些方法:
1.开始加载 xml 配置文件
ApplicationContext context = new ClassPathXmlApplicationContext("test.xml");
2.ApplicationContext 的构造方法
this(new String[] {configLocation}, true, null); public ClassPathXmlApplicationContext( String[] configLocations, boolean refresh, @Nullable ApplicationContext parent) throws BeansException { super(parent); setConfigLocations(configLocations); if (refresh) { refresh(); } }
3.父类构造方法
一直跳转到 AbstractApplicationContext 文件
public AbstractApplicationContext(@Nullable ApplicationContext parent) { this(); setParent(parent); }
其中 this()方法是创建一个新的 AbstractApplicationContext,并生成一个默认的资源模式解析器。因为 parent 为 null,所以 setParent 没有实质作用。
4.设置配置文件路径
返回 ClassPathXmlApplicationContext 查看 setConfigLocations 方法。此方法是将传入的资源路径保存下来。
public void setConfigLocations(@Nullable String... locations) { if (locations != null) { Assert.noNullElements(locations, "Config locations must not be null"); this.configLocations = new String[locations.length]; for (int i = 0; i < locations.length; i++) { this.configLocations[i] = resolvePath(locations[i]).trim(); } } else { this.configLocations = null; } }
5.refresh 方法
主要的 IOC 方法。主要看 spring 的 beanfactory 怎么生成的,以及保存了什么。
@Override public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // 准备此上下文以进行刷新。 prepareRefresh(); // 告诉子类刷新内部bean工厂。 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // 准备在这种情况下使用的Bean工厂。 prepareBeanFactory(beanFactory); try { // 允许在上下文子类中对bean工厂进行后处理。 postProcessBeanFactory(beanFactory); // 调用工厂处理器在上下文中注册为bean。 invokeBeanFactoryPostProcessors(beanFactory); // 注册bean处理器,拦截bean创建。 registerBeanPostProcessors(beanFactory); // Initialize message source for this context. initMessageSource(); // 初始化此上下文的消息源。 initApplicationEventMulticaster(); // 在特定上下文子类中初始化其他特殊bean。 onRefresh(); // Check for listener beans and register them. registerListeners(); // 检查侦听器bean并注册它们。 finishBeanFactoryInitialization(beanFactory); // 最后一步:发布相应的事件。 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(); } } }
6.obtainFreshBeanFactory 方法
在 refreshBeanFactory 生成 beanFactory,然后通过 getBeanFactory 获取
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { refreshBeanFactory(); ConfigurableListableBeanFactory beanFactory = getBeanFactory(); if (logger.isDebugEnabled()) { logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory); } return beanFactory; }
7.refreshBeanFactory 的实现方法
在 idea 中可以使用 ctrl+alt+b 的快捷键查看方法的实现方法。该方法在 AbstractRefreshableApplicationContext 中,
可以看到,方法中先销毁了之前的 beanFactory(如果有的话),然后生成了一个默认的 DefaultListableBeanFactory。然后将 beanFactory 保存,使得上一步的 getBeanFactory 可以获取。然后看 loadBeanDefinitions 方法。
protected final void refreshBeanFactory() throws BeansException { if (hasBeanFactory()) { destroyBeans(); closeBeanFactory(); } try { DefaultListableBeanFactory beanFactory = createBeanFactory(); beanFactory.setSerializationId(getId()); customizeBeanFactory(beanFactory); loadBeanDefinitions(beanFactory); synchronized (this.beanFactoryMonitor) { this.beanFactory = beanFactory; } } catch (IOException ex) { throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex); } }
8.loadBeanDefinitions 方法
这里有很多的 loadBeanDefinitions 在互相调用,这些 loadBeanDefinitions 的作用就是将最开始传入的资源文件路径加载,封装成 InputSource,方便后续解析文件。
//生成一个xml读取器 @Override protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException { // Create a new XmlBeanDefinitionReader for the given BeanFactory. XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory); // Configure the bean definition reader with this context's // resource loading environment. beanDefinitionReader.setEnvironment(this.getEnvironment()); //传入一个资源加载器,就是AbstractXmlApplicationContext 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); loadBeanDefinitions(beanDefinitionReader); } protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException { Resource[] configResources = getConfigResources(); if (configResources != null) { reader.loadBeanDefinitions(configResources); } //用reader读取最开始传入的资源文件路径 String[] configLocations = getConfigLocations(); if (configLocations != null) { reader.loadBeanDefinitions(configLocations); } } @Override public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException { Assert.notNull(locations, "Location array must not be null"); int counter = 0; for (String location : locations) { counter += loadBeanDefinitions(location); } return counter; } @Override public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException { return loadBeanDefinitions(location, null); } public int loadBeanDefinitions(String location, @Nullable Set actualResources) throws BeanDefinitionStoreException { ResourceLoader resourceLoader = getResourceLoader(); if (resourceLoader == null) { throw new BeanDefinitionStoreException( "Cannot import bean definitions from location [" + location + "]: no ResourceLoader available"); } //前面传入了一个资源加载器,可以通过继承树看出AbstractXmlApplicationContext是ResourcePatternResolver的子类 if (resourceLoader instanceof ResourcePatternResolver) { // Resource pattern matching available. try { //将资源文件的路径封装成Resource 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; } } @Override public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException { Assert.notNull(resources, "Resource array must not be null"); int counter = 0; for (Resource resource : resources) { counter += loadBeanDefinitions(resource); } return counter; } @Override public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException { return loadBeanDefinitions(new EncodedResource(resource)); } //封装资源文件和inputstream public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException { Assert.notNull(encodedResource, "EncodedResource must not be null"); if (logger.isInfoEnabled()) { logger.info("Loading XML bean definitions from " + encodedResource.getResource()); } Set 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 { InputStream inputStream = encodedResource.getResource().getInputStream(); try { InputSource inputSource = new InputSource(inputStream); if (encodedResource.getEncoding() != null) { inputSource.setEncoding(encodedResource.getEncoding()); } 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(); } } }
8.doLoadBeanDefinitions 方法
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException { try { //使用前面封装的资源文件和inputSource读取资源文件,并封装为Document对象 Document doc = doLoadDocument(inputSource, resource); return registerBeanDefinitions(doc, resource); } catch (BeanDefinitionStoreException ex) { throw ex; } catch (SAXParseException ex) { throw new XmlBeanDefinitionStoreException(resource.getDescription(), "Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex); } catch (SAXException ex) { throw new XmlBeanDefinitionStoreException(resource.getDescription(), "XML document from " + resource + " is invalid", ex); } catch (ParserConfigurationException ex) { throw new BeanDefinitionStoreException(resource.getDescription(), "Parser configuration exception parsing XML from " + resource, ex); } catch (IOException ex) { throw new BeanDefinitionStoreException(resource.getDescription(), "IOException parsing XML document from " + resource, ex); } catch (Throwable ex) { throw new BeanDefinitionStoreException(resource.getDescription(), "Unexpected exception parsing XML document from " + resource, ex); } }
9.registerBeanDefinitions 方法
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException { //创建一个BeanDefinition读取器 BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader(); int countBefore = getRegistry().getBeanDefinitionCount(); documentReader.registerBeanDefinitions(doc, createReaderContext(resource)); return getRegistry().getBeanDefinitionCount() - countBefore; } @Override public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) { this.readerContext = readerContext; logger.debug("Loading bean definitions"); Element root = doc.getDocumentElement(); doRegisterBeanDefinitions(root); }
10.doRegisterBeanDefinitions
protected void doRegisterBeanDefinitions(Element root) { // Any nested elements will cause recursion in this method. In // order to propagate and preserve default-* attributes correctly, // keep track of the current (parent) delegate, which may be null. Create // the new (child) delegate with a reference to the parent for fallback purposes, // then ultimately reset this.delegate back to its original (parent) reference. // this behavior emulates a stack of delegates without actually necessitating one. BeanDefinitionParserDelegate parent = this.delegate; this.delegate = createDelegate(getReaderContext(), root, parent); if (this.delegate.isDefaultNamespace(root)) { String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE); if (StringUtils.hasText(profileSpec)) { String[] specifiedProfiles = StringUtils.tokenizeToStringArray( profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS); if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) { if (logger.isInfoEnabled()) { logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec + "] not matching: " + getReaderContext().getResource()); } return; } } } preProcessXml(root); //开始解析Document中的Element信息 parseBeanDefinitions(root, this.delegate); postProcessXml(root); this.delegate = parent; }
11.parseBeanDefinitions
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)) { // 使用默认的命名空间解析element parseDefaultElement(ele, delegate); } else { delegate.parseCustomElement(ele); } } } } else { delegate.parseCustomElement(root); } }
12.parseDefaultElement
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) { //注册import标签信息 if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) { importBeanDefinitionResource(ele); } //注册alias标签信息 else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) { processAliasRegistration(ele); } //注册Bean标签信息 else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { processBeanDefinition(ele, delegate); } //解析beans标签信息 else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // recurse doRegisterBeanDefinitions(ele); } }
13.processBeanDefinition
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { //这里已经将配置文件的信息封装为BeanDefinitionHolder,该类保存了BeanDefinition,BeanName和BeanAlices 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)); } }
14.registerBeanDefinition
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); } } }
15.registerBeanDefinition
@Override public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { Assert.hasText(beanName, "Bean name must not be empty"); Assert.notNull(beanDefinition, "BeanDefinition must not be null"); if (beanDefinition instanceof AbstractBeanDefinition) { try { ((AbstractBeanDefinition) beanDefinition).validate(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", ex); } } BeanDefinition oldBeanDefinition; oldBeanDefinition = this.beanDefinitionMap.get(beanName); if (oldBeanDefinition != null) { if (!isAllowBeanDefinitionOverriding()) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName + "': There is already [" + oldBeanDefinition + "] bound."); } else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) { // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE if (this.logger.isWarnEnabled()) { this.logger.warn("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else if (!beanDefinition.equals(oldBeanDefinition)) { if (this.logger.isInfoEnabled()) { this.logger.info("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else { if (this.logger.isDebugEnabled()) { this.logger.debug("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } //将前面封装的BeanDefinitionHolder中的beanName和beanDefinition保存到一个ConcurrentHashMap中 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 updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1); updatedDefinitions.addAll(this.beanDefinitionNames); updatedDefinitions.add(beanName); this.beanDefinitionNames = updatedDefinitions; if (this.manualSingletonNames.contains(beanName)) { Set updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames); updatedSingletons.remove(beanName); this.manualSingletonNames = updatedSingletons; } } } else { // Still in startup registration phase this.beanDefinitionMap.put(beanName, beanDefinition); this.beanDefinitionNames.add(beanName); this.manualSingletonNames.remove(beanName); } this.frozenBeanDefinitionNames = null; } if (oldBeanDefinition != null || containsSingleton(beanName)) { resetBeanDefinition(beanName); } }
终于结束了,可以看到,最后将 beanDefinition 存放在了 beanDefinitionMap 中,而 beanDefinitionMap 就是一个 ConcurrentHashMap 集合。
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