ClassPathResource res =new ClassPathResource(‘beans.xml‘);

public class FileSystemXmlApplicationContext extends AbstractXmlApplicationContext {    /**     * Create a new FileSystemXmlApplicationContext for bean-style configuration.     * @see #setConfigLocation     * @see #setConfigLocations     * @see #afterPropertiesSet()     */    public FileSystemXmlApplicationContext() {    }    /**     * Create a new FileSystemXmlApplicationContext for bean-style configuration.     * @param parent the parent context     * @see #setConfigLocation     * @see #setConfigLocations     * @see #afterPropertiesSet()     */    public FileSystemXmlApplicationContext(ApplicationContext parent) {        super(parent);    }    /**     * Create a new FileSystemXmlApplicationContext, loading the definitions     * from the given XML file and automatically refreshing the context.     * @param configLocation file path     * @throws BeansException if context creation failed     */    //这个构造函数的configLocation包含的是BeanDefinition所在的文件路径    public FileSystemXmlApplicationContext(String configLocation) throws BeansException {        this(new String[] {configLocation}, true, null);    }    /**     * Create a new FileSystemXmlApplicationContext, loading the definitions     * from the given XML files and automatically refreshing the context.     * @param configLocations array of file paths     * @throws BeansException if context creation failed     */    //这个构造函数的configLocation包含多个BeanDefinition的文件路径    public FileSystemXmlApplicationContext(String... configLocations) throws BeansException {        this(configLocations, true, null);    }    /**     * Create a new FileSystemXmlApplicationContext with the given parent,     * loading the definitions from the given XML files and automatically     * refreshing the context.     * @param configLocations array of file paths     * @param parent the parent context     * @throws BeansException if context creation failed     */    //这个构造函数的configLocation包含的多个BeanDefinition文件路径的同时，还允许指定自己的双亲IOC容器    public FileSystemXmlApplicationContext(String[] configLocations, ApplicationContext parent) throws BeansException {        this(configLocations, true, parent);    }    /**     * Create a new FileSystemXmlApplicationContext, loading the definitions     * from the given XML files.     * @param configLocations array of file paths     * @param refresh whether to automatically refresh the context,     * loading all bean definitions and creating all singletons.     * Alternatively, call refresh manually after further configuring the context.     * @throws BeansException if context creation failed     * @see #refresh()     */    public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh) throws BeansException {        this(configLocations, refresh, null);    }    /**     * Create a new FileSystemXmlApplicationContext with the given parent,     * loading the definitions from the given XML files.     * @param configLocations array of file paths     * @param refresh whether to automatically refresh the context,     * loading all bean definitions and creating all singletons.     * Alternatively, call refresh manually after further configuring the context.     * @param parent the parent context     * @throws BeansException if context creation failed     * @see #refresh()     */    //在对象的初始化过程中，调用refresh方法载入BeanDefinition，这个refresh方法启动了BeanDefinition的载入过程，待会看refresh详细分析    public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)            throws BeansException {        super(parent);        setConfigLocations(configLocations);        if (refresh) {            refresh();        }    }    /**     * Resolve resource paths as file system paths.     * <p>Note: Even if a given path starts with a slash, it will get     * interpreted as relative to the current VM working directory.     * This is consistent with the semantics in a Servlet container.     * @param path path to the resource     * @return Resource handle     * @see org.springframework.web.context.support.XmlWebApplicationContext#getResourceByPath     */    @Override    //这是应用于文件系统中的Resource的实现，通过构造一个FileSystemResource来得到一个文件在    //系统中定位的BeanDefinition    //这个getResourceByPath是在BeanDefinitionReader的loadBeanDefinition中被调用    //loadBeanDefinition采用模板模式，具体的定位实现是由各个子类来完成    protected Resource getResourceByPath(String path) {        if (path != null && path.startsWith("/")) {            path = path.substring(1);        }        return new FileSystemResource(path);    }}

    public void refresh() throws BeansException, IllegalStateException {        synchronized (this.startupShutdownMonitor) {            // Prepare this context for refreshing.            prepareRefresh();            // Tell the subclass to refresh the internal bean factory.            //子类中启动refreshBeanFactory的地方            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.                //设置beanFactory的后置处理                postProcessBeanFactory(beanFactory);                                // Invoke factory processors registered as beans in the context.                //调用beanFactory的后置处理器，这些后处理器在bean中向容器注册的                invokeBeanFactoryPostProcessors(beanFactory);                                // Register bean processors that intercept bean creation.                //注册bean的后处理器，在bean创建过程中调用                registerBeanPostProcessors(beanFactory);                // Initialize message source for this context.                //对上下文中的消息源进行初始化                initMessageSource();                // Initialize event multicaster for this context.                //初始化上下文中的事件机制                initApplicationEventMulticaster();                // Initialize other special beans in specific context subclasses.                //初始化其中的特殊bean                onRefresh();                // Check for listener beans and register them.                //检查监听bean并且将这些bean向容器注册                registerListeners();                // Instantiate all remaining (non-lazy-init) singletons.                //实例化所有non-lazy-init单件                finishBeanFactoryInitialization(beanFactory);                // Last step: publish corresponding event.                //发布容器事件，结束refresh过程                finishRefresh();            }            catch (BeansException ex) {                // Destroy already created singletons to avoid dangling resources.                //为防止bean资源占用，在异常处理中，销毁已经在前面过程中生成的单件bean                destroyBeans();                // Reset ‘active‘ flag.                //重置active标志                cancelRefresh(ex);                // Propagate exception to caller.                throw ex;            }        }    }

    protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {        refreshBeanFactory();        ConfigurableListableBeanFactory beanFactory = getBeanFactory();        if (logger.isDebugEnabled()) {            logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);        }        return beanFactory;    }

protected final void refreshBeanFactory() throws BeansException {        if (hasBeanFactory()) {            destroyBeans();            closeBeanFactory();        }        try {            //创建ioc容器,DefaultListableBeanFactory            DefaultListableBeanFactory beanFactory = createBeanFactory();            beanFactory.setSerializationId(getId());            customizeBeanFactory(beanFactory);            //启动对BeanDefinition的载入            loadBeanDefinitions(beanFactory);            synchronized (this.beanFactoryMonitor) {                this.beanFactory = beanFactory;            }        }        catch (IOException ex) {            throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);        }    }

//这就是在上下文中创建DefaultListableBeanFactory的地方，getInternalParentBeanFactory()的具体实现在    //AbstractApplicationContext，会根据已有的双亲IOC容器信息来完成DefaultListableBeanFactory的双亲IOC容器    protected DefaultListableBeanFactory createBeanFactory() {        return new DefaultListableBeanFactory(getInternalParentBeanFactory());    }    /**     *      *     protected BeanFactory getInternalParentBeanFactory() {              return (getParent() instanceof ConfigurableApplicationContext) ?                     ((ConfigurableApplicationContext) getParent()).getBeanFactory() : getParent();    }     */

/**     * Load bean definitions into the given bean factory, typically through     * delegating to one or more bean definition readers.     * @param beanFactory the bean factory to load bean definitions into     * @throws BeansException if parsing of the bean definitions failed     * @throws IOException if loading of bean definition files failed     * @see org.springframework.beans.factory.support.PropertiesBeanDefinitionReader     * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader     */    //这里是使用 BeanDefinitionReader载入Bean定义的地方，因为允许有多种载入方式，虽然用的最多的是XML定义的形式，    //这里通过一个抽象函数把具体的实现委托给子类完成    protected abstract void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)            throws BeansException, IOException;

    public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {        //取得ResourceLoader使用的是DefaultResourceLoader        ResourceLoader resourceLoader = getResourceLoader();        if (resourceLoader == null) {            throw new BeanDefinitionStoreException(                    "Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");        }        //对Resource路径解析，Resource集合可以是多个文件        if (resourceLoader instanceof ResourcePatternResolver) {            // Resource pattern matching available.            try {                //取得具体的Resource定位                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;        }    }

public Resource getResource(String location) {        Assert.notNull(location, "Location must not be null");        if (location.startsWith(CLASSPATH_URL_PREFIX)) { //     public static final String CLASSPATH_URL_PREFIX = "classpath:";            return new ClassPathResource(location.substring(CLASSPATH_URL_PREFIX.length()), getClassLoader());        }        else {            try {                // Try to parse the location as a URL...                //这里处理URL标识的Resource定位                URL url = new URL(location);                return new UrlResource(url);            }            catch (MalformedURLException ex) {                // No URL -> resolve as resource path.                //如果既不是classpath，也不是URL标识的Resource定位，则把getResource交给getResourceByPath，                //这个方法是一个protected方法，默认实现是得到一个ClassPathContextResource，这个方法会用子类实现                return getResourceByPath(location);            }        }    }

    protected Resource getResourceByPath(String path) {        return new ClassPathContextResource(path, getClassLoader());    }

    @Override    //这是应用于文件系统中的Resource的实现，通过构造一个FileSystemResource来得到一个文件在    //系统中定位的BeanDefinition    //这个getResourceByPath是在BeanDefinitionReader的loadBeanDefinition中被调用    //loadBeanDefinition采用模板模式，具体的定位实现是由各个子类来完成    protected Resource getResourceByPath(String path) {        if (path != null && path.startsWith("/")) {            path = path.substring(1);        }        return new FileSystemResource(path);    }