擷取XMlL的驗證模式

XML驗證模式有2種：DTD（Document Type Definition）和XSD（XML Schemas Definition）。

驗證模式的讀取：

protected int getValidationModeForResource(Resource resource) {
		int validationModeToUse = getValidationMode();
		if (validationModeToUse != VALIDATION_AUTO) {
			return validationModeToUse;
		}
		int detectedMode = detectValidationMode(resource);
		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;
	}
           

如果設定了驗證模式則使用驗證模式，否則使用自動檢測的方式。而自動檢測驗證模式的功能是在函數detectValidationMode方法中實作的，在detectValidationMode函數中又将自動檢測驗證模式的工作委托給了專門處理類XmlValidationModeDetector類。

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();
		}
		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 {
			return this.validationModeDetector.detectValidationMode(inputStream);
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException("Unable to determine validation mode for [" +
					resource + "]: an error occurred whilst reading from the InputStream.", ex);
		}
	}
           

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;
			while ((content = reader.readLine()) != null) {
				content = consumeCommentTokens(content);
				if (this.inComment || !StringUtils.hasText(content)) {
					continue;
				}
				if (hasDoctype(content)) {
					isDtdValidated = true;
					break;
				}
				if (hasOpeningTag(content)) {
					// End of meaningful data...
					break;
				}
			}
			return (isDtdValidated ? VALIDATION_DTD : VALIDATION_XSD);
		}
		catch (CharConversionException ex) {
			// Choked on some character encoding...
			// Leave the decision up to the caller.
			return VALIDATION_AUTO;
		}
		finally {
			reader.close();
		}
	}
           

private boolean hasDoctype(String content) {
		return (content.indexOf(DOCTYPE) > -1);
	}
           

spring用來檢測驗證模式的辦法就是判斷是否包含DOCTYPE，如果包含就是DTD，否則就是XSD。