解析Spring源码（5）--this.documentLoader.loadDocument

承接上一篇。。。

    /**     * private DocumentLoader documentLoader = new DefaultDocumentLoader();     * 对象解析文件流     *      * Actually load the specified document using the configured DocumentLoader.     * @param inputSource the SAX InputSource to read from     * @param resource the resource descriptor for the XML file     * @return the DOM Document     * @throws Exception when thrown from the DocumentLoader     * @see #setDocumentLoader     * @see DocumentLoader#loadDocument     */    protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {        return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,                getValidationModeForResource(resource), isNamespaceAware());    }

这个调用，使用的参数很多！让我们一一进行分析。。。

• getEntityResolver()

    /**     *将 ResourceLoader resourceLoader 对象封装，返回     * Return the EntityResolver to use, building a default resolver     * if none specified.     */    protected EntityResolver getEntityResolver() {        if (this.entityResolver == null) {            // Determine default EntityResolver to use.创建reader对象时进行过初始化，获取到封装类加载器的对象            ResourceLoader resourceLoader = getResourceLoader();            if (resourceLoader != null) {                //又把resourceLoader封装了，赋值entityResolver                this.entityResolver = new ResourceEntityResolver(resourceLoader);            }            else {                this.entityResolver = new DelegatingEntityResolver(getBeanClassLoader());            }        }        return this.entityResolver;    }

上面同时也调用了很多方法，先不一一介绍以免混乱

• getValidationModeForResource(resource)

        /**     * 对xml文件的验证模式dtd,xsd判断选择     * Gets the validation mode for the specified {@link Resource}. If no explicit     * validation mode has been configured then the validation mode is     * {@link #detectValidationMode detected}.     * <p>Override this method if you would like full control over the validation     * mode, even when something other than {@link #VALIDATION_AUTO} was set.     */    protected int getValidationModeForResource(Resource resource) {        /**private int validationMode = VALIDATION_AUTO;         *public static final int VALIDATION_AUTO = 1;         *public static final int VALIDATION_AUTO = XmlValidationModeDetector.VALIDATION_AUTO;         */        int validationModeToUse = getValidationMode();//1        if (validationModeToUse != VALIDATION_AUTO) {            return validationModeToUse;        }        int detectedMode = detectValidationMode(resource);//3        if (detectedMode != VALIDATION_AUTO) {            return detectedMode;        }        // Hmm, we didn't get a clear indication... Let's assume XSD,        // since apparently no DTD declaration has been found up until        // detection stopped (before finding the document's root tag).        return VALIDATION_XSD;    }    /**     * Detects which kind of validation to perform on the XML file identified     * by the supplied {@link Resource}. If the file has a {@code DOCTYPE}     * definition then DTD validation is used otherwise XSD validation is assumed.     * <p>Override this method if you would like to customize resolution     * of the {@link #VALIDATION_AUTO} mode.     */    protected int detectValidationMode(Resource resource) {        if (resource.isOpen()) {            throw new BeanDefinitionStoreException(                    "Passed-in Resource [" + resource + "] contains an open stream: " +                    "cannot determine validation mode automatically. Either pass in a Resource " +                    "that is able to create fresh streams, or explicitly specify the validationMode " +                    "on your XmlBeanDefinitionReader instance.");        }        InputStream inputStream;        try {            inputStream = resource.getInputStream();//输入流        }        catch (IOException ex) {            throw new BeanDefinitionStoreException(                    "Unable to determine validation mode for [" + resource + "]: cannot open InputStream. " +                    "Did you attempt to load directly from a SAX InputSource without specifying the " +                    "validationMode on your XmlBeanDefinitionReader instance?", ex);        }        try {            //  private final XmlValidationModeDetector validationModeDetector = new XmlValidationModeDetector();            return this.validationModeDetector.detectValidationMode(inputStream);//3        }        catch (IOException ex) {            throw new BeanDefinitionStoreException("Unable to determine validation mode for [" +                    resource + "]: an error occurred whilst reading from the InputStream.", ex);        }    }

    /**     * 返回验证模式，此为3，xsd     * Detect the validation mode for the XML document in the supplied {@link InputStream}.     * Note that the supplied {@link InputStream} is closed by this method before returning.     * @param inputStream the InputStream to parse     * @throws IOException in case of I/O failure     * @see #VALIDATION_DTD     * @see #VALIDATION_XSD     */    public int detectValidationMode(InputStream inputStream) throws IOException {        // Peek into the file to look for DOCTYPE.        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));        try {            boolean isDtdValidated = false;            String content;            //读取xml文件            while ((content = reader.readLine()) != null) {                content = consumeCommentTokens(content);//不变                if (this.inComment || !StringUtils.hasText(content)) {//inComment==false,没读取到内容跳回循环                    continue;                }                if (hasDoctype(content)) {//是否包含Doctype                    isDtdValidated = true;                    break;                }                if (hasOpeningTag(content)) {                    // End of meaningful data...                    break;                }            }            return (isDtdValidated ? VALIDATION_DTD : VALIDATION_XSD);//返回3        }        catch (CharConversionException ex) {            // Choked on some character encoding...            // Leave the decision up to the caller.            return VALIDATION_AUTO;        }        finally {            reader.close();        }    }

• isNamespaceAware()

    private boolean namespaceAware = false;    public boolean isNamespaceAware() {        return this.namespaceAware;    }