初探spring applicationContext在web容器中加载过程

首先从WEB.XML入手 ==>web.xml <context-param> <param-name>webAppRootKey</param-name> <param-value>task.root</param-value> </context-param> <!-- 定义SPRING配置文件 --> <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/taskContext*.xml</param-value> </context-param> <context-param> <param-name>log4jConfigLocation</param-name> <param-value>/WEB-INF/log4j.properties</param-value> </context-param> <!-- 定义LOG4J监听器 --> <listener> <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class> </listener> <!-- 定义SPRING监听器 --> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> 进入contextLoaderListener看看到底加载时做了甚么 ==>org.springframework.web.context.ContextLoaderListener public class ContextLoaderListener implements ServletContextListener { private ContextLoader contextLoader; /** * Initialize the root web application context. */ //当WEB上下文初始化时,系统会调用此方法 public void contextInitialized(ServletContextEvent event) { this.contextLoader = createContextLoader(); //监听到WEB上下文初始化的时候执行SPRING上下文contextLoader的初始化工作 this.contextLoader.initWebApplicationContext(event.getServletContext()); } /** * Create the ContextLoader to use. Can be overridden in subclasses. * @return the new ContextLoader */ protected ContextLoader createContextLoader() { return new ContextLoader(); } /** * Return the ContextLoader used by this listener. */ public ContextLoader getContextLoader() { return contextLoader; } /** * Close the root web application context. */ public void contextDestroyed(ServletContextEvent event) { if (this.contextLoader != null) { this.contextLoader.closeWebApplicationContext(event.getServletContext()); } } } 看一下是怎么来初始化webapplicationContext的 ==>contextLoader.initWebApplicationContext public WebApplicationContext initWebApplicationContext(ServletContext servletContext) throws IllegalStateException, BeansException { if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) { throw new IllegalStateException( "Cannot initialize context because there is already a root application context present - " + "check whether you have multiple ContextLoader* definitions in your web.xml!"); } long startTime = System.currentTimeMillis(); if (logger.isInfoEnabled()) { logger.info("Root WebApplicationContext: initialization started"); } servletContext.log("Loading Spring root WebApplicationContext"); try { // Determine parent for root web application context, if any. ApplicationContext parent = loadParentContext(servletContext); // Store context in local instance variable, to guarantee that // it is available on ServletContext shutdown. //创建web上下文 this.context = createWebApplicationContext(servletContext, parent); servletContext.setAttribute( WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context); if (logger.isInfoEnabled()) { logger.info("Using context class [" + this.context.getClass().getName() + "] for root WebApplicationContext"); } if (logger.isDebugEnabled()) { logger.debug("Published root WebApplicationContext [" + this.context + "] as ServletContext attribute with name [" + WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]"); } if (logger.isInfoEnabled()) { long elapsedTime = System.currentTimeMillis() - startTime; logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms"); } return this.context; } catch (RuntimeException ex) { logger.error("Context initialization failed", ex); servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex); throw ex; } catch (Error err) { logger.error("Context initialization failed", err); servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err); throw err; } } ==>contextLoader.createWebApplicationContext(servletContext, parent); protected WebApplicationContext createWebApplicationContext( ServletContext servletContext, ApplicationContext parent) throws BeansException { //根据servletContext来决定要实例化的WebApplicationContext Class contextClass = determineContextClass(servletContext); if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) { throw new ApplicationContextException("Custom context class [" + contextClass.getName() + "] is not of type ConfigurableWebApplicationContext"); } ConfigurableWebApplicationContext wac = (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass); wac.setParent(parent); wac.setServletContext(servletContext); //得到WEB.XML中设置的SPRING配置文件位置 String configLocation = servletContext.getInitParameter(CONFIG_LOCATION_PARAM); if (configLocation != null) { //把配置文件分段后设置到WebApplicationContext的ConfigLocations中 wac.setConfigLocations(StringUtils.tokenizeToStringArray(configLocation, ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS)); } //刷新WebApplicationContext wac.refresh(); return wac; } ==>contextLoader.determineContextClass(servletContext); protected Class determineContextClass(ServletContext servletContext) throws ApplicationContextException { //获得需要实例化的CONTEXT类名,在web.xml中有设置,如果没有设置,那么为空 String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM); if (contextClassName != null) { try { return ClassUtils.forName(contextClassName); } catch (ClassNotFoundException ex) { throw new ApplicationContextException( "Failed to load custom context class [" + contextClassName + "]", ex); } } //如果在spring web.xml中没有设置context类位置,那么取得默认context else { //取得defaultStrategies配置文件中的WebApplicationContext属性 contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName()); try { return ClassUtils.forName(contextClassName); } catch (ClassNotFoundException ex) { throw new ApplicationContextException( "Failed to load default context class [" + contextClassName + "]", ex); } } } SPRING上下文默认的策略是甚么呢? ==>contextLoader.defaultStrategies private static final Properties defaultStrategies; static { // Load default strategy implementations from properties file. // This is currently strictly internal and not meant to be customized // by application developers. try { //设置classpath为contextLoader同级目录 ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class); //加载该目录下的所有properties文件 defaultStrategies = PropertiesLoaderUtils.loadProperties(resource); } catch (IOException ex) { throw new IllegalStateException("Could not load 'ContextLoader.properties': " + ex.getMessage()); } } 找到同级目录下的配置文件 ==>ContextLoader.properties # Default WebApplicationContext implementation class for ContextLoader. Used as fallback when no explicit context implementation has been specified as context-param. Not meant to be customized by application developers. #默认的WebApplicationContext为org.springframework.web.context.support.XmlWebApplicationContext org.springframework.web.context.WebApplicationContext=org.springframework.web.context.support.XmlWebApplicationContext ==>org.springframework.web.context.support.XmlWebApplicationContext public class XmlWebApplicationContext extends AbstractRefreshableWebApplicationContext { /** Default config location for the root context */ //配置了默认的spring配置文件 public static final String DEFAULT_CONFIG_LOCATION = "/WEB-INF/applicationContext.xml"; //配置文件默认BUILD路径 public static final String DEFAULT_CONFIG_LOCATION_PREFIX = "/WEB-INF/"; //配置文件默认后缀名 public static final String DEFAULT_CONFIG_LOCATION_SUFFIX = ".xml"; /** * Loads the bean definitions via an XmlBeanDefinitionReader. * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader * @see #initBeanDefinitionReader * @see #loadBeanDefinitions */ //获得bean配置 protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws IOException { //从BEAN工厂获得一个XmlBeanDefinitionReader 来读取SPRING配置文件 XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory); //设置beanDefinitionReader服务于当前CONTEXT // resource loading environment. 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); //读取配置文件 loadBeanDefinitions(beanDefinitionReader); } /** * Initialize the bean definition reader used for loading the bean * definitions of this context. Default implementation is empty. * <p>Can be overridden in subclasses, e.g. for turning off XML validation * or using a different XmlBeanDefinitionParser implementation. * @param beanDefinitionReader the bean definition reader used by this context * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader#setValidationMode * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader#setDocumentReaderClass */ protected void initBeanDefinitionReader(XmlBeanDefinitionReader beanDefinitionReader) { } /** * Load the bean definitions with the given XmlBeanDefinitionReader. * <p>The lifecycle of the bean factory is handled by the refreshBeanFactory method; * therefore this method is just supposed to load and/or register bean definitions. * <p>Delegates to a ResourcePatternResolver for resolving location patterns * into Resource instances. * @throws org.springframework.beans.BeansException in case of bean registration errors * @throws java.io.IOException if the required XML document isn't found * @see #refreshBeanFactory * @see #getConfigLocations * @see #getResources * @see #getResourcePatternResolver */ //读取配置文件 protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException { String[] configLocations = getConfigLocations(); if (configLocations != null) { for (int i = 0; i < configLocations.length; i++) { reader.loadBeanDefinitions(configLocations[i]); } } } /** * The default location for the root context is "/WEB-INF/applicationContext.xml", * and "/WEB-INF/test-servlet.xml" for a context with the namespace "test-servlet" * (like for a DispatcherServlet instance with the servlet-name "test"). */ //获得默认的ConfigLocations protected String[] getDefaultConfigLocations() { if (getNamespace() != null) { return new String[] {DEFAULT_CONFIG_LOCATION_PREFIX + getNamespace() + DEFAULT_CONFIG_LOCATION_SUFFIX}; } else { return new String[] {DEFAULT_CONFIG_LOCATION}; } } ==>AbstractBeanDefinitionReader.loadBeanDefinitions() public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException { ResourceLoader resourceLoader = getResourceLoader(); if (resourceLoader == null) { throw new BeanDefinitionStoreException( "Cannot import bean definitions from location [" + location + "]: no ResourceLoader available"); } if (resourceLoader instanceof ResourcePatternResolver) { // Resource pattern matching available. try { //根据配置文件读取相应配置 Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location); int loadCount = loadBeanDefinitions(resources); 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 (logger.isDebugEnabled()) { logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]"); } return loadCount; } } 这个是其中一个ResourceLoader的实现 ==>PathMatchingResourcePatternResolver.getResources(String locationPattern); public Resource[] getResources(String locationPattern) throws IOException { Assert.notNull(locationPattern, "Location pattern must not be null"); if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) { // a class path resource (multiple resources for same name possible) if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) { // a class path resource pattern return findPathMatchingResources(locationPattern); } else { // all class path resources with the given name return findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length())); } } else { // Only look for a pattern after a prefix here // (to not get fooled by a pattern symbol in a strange prefix). int prefixEnd = locationPattern.indexOf(":") + 1; if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) { // a file pattern return findPathMatchingResources(locationPattern); } else { // a single resource with the given name return new Resource[] {getResourceLoader().getResource(locationPattern)}; } } } ==>PathMatchingResourcePatternResolver.findPathMatchingResources(String locationPattern); protected Resource[] findPathMatchingResources(String locationPattern) throws IOException { String rootDirPath = determineRootDir(locationPattern); String subPattern = locationPattern.substring(rootDirPath.length()); Resource[] rootDirResources = getResources(rootDirPath); //collectionFactory初始化一个set容量为16 Set result = CollectionFactory.createLinkedSetIfPossible(16); for (int i = 0; i < rootDirResources.length; i++) { Resource rootDirResource = rootDirResources[i]; if (isJarResource(rootDirResource)) { result.addAll(doFindPathMatchingJarResources(rootDirResource, subPattern)); } else { result.addAll(doFindPathMatchingFileResources(rootDirResource, subPattern)); } } if (logger.isDebugEnabled()) { logger.debug("Resolved location pattern [" + locationPattern + "] to resources " + result); } return (Resource[]) result.toArray(new Resource[result.size()]); } 前面说到有一个刷新WebApplicationContext的操作,但是XmlWebApplicationContext 并没有实现refresh方法,而方法的实现写在 AbstractRefreshableWebApplicationContext 中 ==>AbstractRefreshableWebApplicationContext.refresh(); public void refresh() throws BeansException { if (ObjectUtils.isEmpty(getConfigLocations())) { //设置configLocations为默认的getDefaultConfigLocations() setConfigLocations(getDefaultConfigLocations()); } super.refresh(); } ==>AbstractApplicationContext.refresh(); public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { this.startupTime = System.currentTimeMillis(); synchronized (this.activeMonitor) { this.active = true; } // Tell subclass to refresh the internal bean factory. refreshBeanFactory(); ConfigurableListableBeanFactory beanFactory = getBeanFactory(); // Tell the internal bean factory to use the context's class loader. beanFactory.setBeanClassLoader(getClassLoader()); // Populate the bean factory with context-specific resource editors. beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this)); // Configure the bean factory with context semantics. beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this)); beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class); beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class); beanFactory.ignoreDependencyInterface(MessageSourceAware.class); beanFactory.ignoreDependencyInterface(ApplicationContextAware.class); // Allows post-processing of the bean factory in context subclasses. postProcessBeanFactory(beanFactory); // Invoke factory processors registered with the context instance. for (Iterator it = getBeanFactoryPostProcessors().iterator(); it.hasNext();) { BeanFactoryPostProcessor factoryProcessor = (BeanFactoryPostProcessor) it.next(); factoryProcessor.postProcessBeanFactory(beanFactory); } if (logger.isInfoEnabled()) { if (getBeanDefinitionCount() == 0) { logger.info("No beans defined in application context [" + getDisplayName() + "]"); } else { logger.info(getBeanDefinitionCount() + " beans defined in application context [" + getDisplayName() + "]"); } } try { // Invoke factory processors registered as beans in the context. invokeBeanFactoryPostProcessors(); // Register bean processors that intercept bean creation. registerBeanPostProcessors(); // 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 singletons this late to allow them to access the message source. beanFactory.preInstantiateSingletons(); // Last step: publish corresponding event. publishEvent(new ContextRefreshedEvent(this)); } catch (BeansException ex) { // Destroy already created singletons to avoid dangling resources. beanFactory.destroySingletons(); throw ex; } } }