Spring 源码解析（二）加载配置文件2

接上一章，我们来具体分析下configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc)方法

 //org.springframework.web.context.ContextLoader.class
 1     protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
        if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
            // The application context id is still set to its original default value
            // -> assign a more useful id based on available information
            String idParam = sc.getInitParameter(CONTEXT_ID_PARAM);
            if (idParam != null) {
 7                 wac.setId(idParam);
            }
            else {
                // Generate default id...
                wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
                        ObjectUtils.getDisplayString(sc.getContextPath()));
            }
        }

16         wac.setServletContext(sc);
        String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
        if (configLocationParam != null) {
           wac.setConfigLocation(configLocationParam);
        }

        // The wac environment's #initPropertySources will be called in any case when the context
        // is refreshed; do it eagerly here to ensure servlet property sources are in place for
        // use in any post-processing or initialization that occurs below prior to #refresh
        ConfigurableEnvironment env = wac.getEnvironment();
        if (env instanceof ConfigurableWebEnvironment) {
            ((ConfigurableWebEnvironment) env).initPropertySources(sc, null);
        }

        customizeContext(sc, wac);
31         wac.refresh(); //刷新容器32     }

第16行，将servletContext设置到WebApplicationContext中，结合前面的分析，通过这里的设置servletContext和WebApplicationContext就可以互相方法了。

第17行，获取配置文件路径，如果在web.xml配置了contextConfigLocation参数，通过19行设置到WebApplicationContext。

第25-28行，创建环境对象。

第31行，刷新容器，spring初始化主要集中在这个方法，进入方法（org.springframework.context.support.AbstractApplicationContext）

 //org.springframework.context.support.AbstractApplicationContext
 1 @Override
    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) {
                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset 'active' flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }
        }
    }

第8行，创建beanFactory，根据spring配置文件初始化得到BeanDefinitions,进入方法(org.springframework.context.support.AbstractApplicationContext类中的方法)

 //org.springframework.context.support.AbstractApplicationContext 
 1     /**
     * Tell the subclass to refresh the internal bean factory.
     * @return the fresh BeanFactory instance
     * @see #refreshBeanFactory()
     * @see #getBeanFactory()
     */
    protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
        refreshBeanFactory();
        ConfigurableListableBeanFactory beanFactory = getBeanFactory();
        if (logger.isDebugEnabled()) {
            logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
        }
        return beanFactory;
    }

进入refreshBeanFactory()方法（org.springframework.context.support.AbstractRefreshableApplicationContext类中的方法）

 //org.springframework.context.support.AbstractRefreshableApplicationContext.class
 1     /**
     * This implementation performs an actual refresh of this context's underlying
     * bean factory, shutting down the previous bean factory (if any) and
     * initializing a fresh bean factory for the next phase of the context's lifecycle.
     */
    @Override
    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);
        }
    }

第13行，创建了DefaultListableBeanFactory，Spring的核心
第16行，加载配置文件，初始化DefaultListableBeanFactory

第18行，将DefaultListableBeanFactory设置到this.beanFactory(在AbstractRefreshableApplicationContext中定义的)

 进入loadBeanDefinitions(beanFatory)方法（org.springframework.web.context.support.XmlWebApplicationContext类中的方法）

 //org.springframework.web.context.support.XmlWebApplicationContext
 1     /**
     * Loads the bean definitions via an XmlBeanDefinitionReader.
     * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
     * @see #initBeanDefinitionReader
     * @see #loadBeanDefinitions
     */
    @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(getEnvironment());
        beanDefinitionReader.setResourceLoader(this);
        beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

        // Allow a subclass to provide custom initialization of the reader,
        // then proceed with actually loading the bean definitions.
        initBeanDefinitionReader(beanDefinitionReader);
        loadBeanDefinitions(beanDefinitionReader);
    }

这个方法主要工作就是定义并初始了XmlBeanDefinitionReader实例。

注意15行，是把this（XmlWebApplicationContext实例）设置到了XmlBeanDefinitionReader实例中，进入loadBeanDefinitions(beanDefinitionReader)方法

 //org.springframework.web.context.support.XmlWebApplicationContext
 1     /**
     * 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 java.io.IOException if the required XML document isn't found
     * @see #refreshBeanFactory
     * @see #getConfigLocations
     * @see #getResources
     * @see #getResourcePatternResolver
     */
    protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws IOException {
        String[] configLocations = getConfigLocations();
        if (configLocations != null) {
            for (String configLocation : configLocations) {
                reader.loadBeanDefinitions(configLocation);
            }
        }
    }

第14行，获取配置文件，可以看出获取了多个配置文件，这就解释了在web.xml中contextConfigLocation参数值可以配置多个xml文件。如果web.xml没有设置配置文件，则默认配置文件为：/WEB-INF/applicationContext.xml，这个通过跟踪getConfigLocations()不难发现，这个留给大家自行跟踪查看。

然后调用XmlBeanDefinitionReader实例，依次解析配置文件。

下一章我们就重分析XmlBeanDefinitionReader实例如何解析配置文件。

★★★友情提示★★★

XmlWebApplicationContext类继承结构：