spring源码解析-2

继续上一篇说的loadBeanDefinitions(EncodedResource encodedResource)方法，

    /**
	 * Load bean definitions from the specified XML file.
	 * @param encodedResource the resource descriptor for the XML file,
	 * allowing to specify an encoding to use for parsing the file
	 * @return the number of bean definitions found
	 * @throws BeanDefinitionStoreException in case of loading or parsing errors
	 */
	public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
		Assert.notNull(encodedResource, "EncodedResource must not be null");
		if (logger.isTraceEnabled()) {
			logger.trace("Loading XML bean definitions from " + encodedResource);
		}

		Set currentResources = this.resourcesCurrentlyBeingLoaded.get();
		if (currentResources == null) {
			currentResources = new HashSet<>(4);
			this.resourcesCurrentlyBeingLoaded.set(currentResources);
		}
		if (!currentResources.add(encodedResource)) {
			throw new BeanDefinitionStoreException(
					"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
		}
		try {
			InputStream inputStream = encodedResource.getResource().getInputStream();
			try {
				InputSource inputSource = new InputSource(inputStream);
				if (encodedResource.getEncoding() != null) {
					inputSource.setEncoding(encodedResource.getEncoding());
				}
				return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
			}
			finally {
				inputStream.close();
			}
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException(
					"IOException parsing XML document from " + encodedResource.getResource(), ex);
		}
		finally {
			currentResources.remove(encodedResource);
			if (currentResources.isEmpty()) {
				this.resourcesCurrentlyBeingLoaded.remove();
			}
		}
	}

获取inputSource，以及Resource对象，执行doLoadBeanDefinitions(inputSource, encodedResource.getResource());
继续往下看这方法:

    /**
	 * Actually load bean definitions from the specified XML file.
	 * @param inputSource the SAX InputSource to read from
	 * @param resource the resource descriptor for the XML file
	 * @return the number of bean definitions found
	 * @throws BeanDefinitionStoreException in case of loading or parsing errors
	 * @see #doLoadDocument
	 * @see #registerBeanDefinitions
	 */
	protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
			throws BeanDefinitionStoreException {

		try {
			Document doc = doLoadDocument(inputSource, resource);
			int count = registerBeanDefinitions(doc, resource);
			if (logger.isDebugEnabled()) {
				logger.debug("Loaded " + count + " bean definitions from " + resource);
			}
			return count;
		}
		catch (BeanDefinitionStoreException ex) {
			throw ex;
		}
		catch (SAXParseException ex) {
			throw new XmlBeanDefinitionStoreException(resource.getDescription(),
					"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
		}
		catch (SAXException ex) {
			throw new XmlBeanDefinitionStoreException(resource.getDescription(),
					"XML document from " + resource + " is invalid", ex);
		}
		catch (ParserConfigurationException ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"Parser configuration exception parsing XML from " + resource, ex);
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"IOException parsing XML document from " + resource, ex);
		}
		catch (Throwable ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"Unexpected exception parsing XML document from " + resource, ex);
		}
	}

2个方法的执行，doLoadDocument(inputSource, resource)，registerBeanDefinitions(doc, resource)，
先看下**doLoadDocument(inputSource, resource)**这方法:

    /**
	 * 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());
	}

这边大概的意思主要是xml文件的格式是否正确，需要个验证模式，XSD或者DTD，是xml文件的一部分，
看下xsd即xml schema语言的表现形式

xmlns=“http://www.springframework.org/schema/beans” 名称空间
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
xml schema文档的存储位置，一部分是uri，另外一部分是文件位置
继续往下走

    /*
	 * Return the EntityResolver to use, building a default resolver
	 * if none specified.
	 */
	protected EntityResolver getEntityResolver() {`在这里插入代码片`
		if (this.entityResolver == null) {
			// Determine default EntityResolver to use.
			ResourceLoader resourceLoader = getResourceLoader();
			if (resourceLoader != null) {
				this.entityResolver = new ResourceEntityResolver(resourceLoader);
			}
			else {
				this.entityResolver = new DelegatingEntityResolver(getBeanClassLoader());
			}
		}
		return this.entityResolver;
	}

下面是**new ResourceEntityResolver(resourceLoader)**的具体执行

    /**
 	 * Create a new DelegatingEntityResolver that delegates to
	 * a default {@link BeansDtdResolver} and a default {@link PluggableSchemaResolver}.
	 * 
Configures the {@link PluggableSchemaResolver} with the supplied
	 * {@link ClassLoader}.
	 * @param classLoader the ClassLoader to use for loading
	 * (can be {@code null}) to use the default ClassLoader)
	 */
	public DelegatingEntityResolver(@Nullable ClassLoader classLoader) {
		this.dtdResolver = new BeansDtdResolver();
		this.schemaResolver = new PluggableSchemaResolver(classLoader);
	}

其实就是生成2种文件格式的解析器

    ResourceLoader resourceLoader = getResourceLoader();

这边有必要说下getResourceLoader()这方法是在父类定义的，子类直接继承调用了，关于他的赋值，是在xmlFactory类初始化XmlBeanDefinitionReader的时候,spring框架里面很多地方用了这种方式，所以看源码的时候，要看仔细了，不然都不知道在哪set的值

	private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);

    /**
	 * Create new XmlBeanDefinitionReader for the given bean factory.
	 * @param registry the BeanFactory to load bean definitions into,
	 * in the form of a BeanDefinitionRegistry
	 */
	public XmlBeanDefinitionReader(BeanDefinitionRegistry registry) {
		super(registry);
	}

    /**
	 * Create a new AbstractBeanDefinitionReader for the given bean factory.
	 * 
If the passed-in bean factory does not only implement the BeanDefinitionRegistry
	 * interface but also the ResourceLoader interface, it will be used as default
	 * ResourceLoader as well. This will usually be the case for
	 * {@link org.springframework.context.ApplicationContext} implementations.
	 * 
If given a plain BeanDefinitionRegistry, the default ResourceLoader will be a
	 * {@link org.springframework.core.io.support.PathMatchingResourcePatternResolver}.
	 * 
If the passed-in bean factory also implements {@link EnvironmentCapable} its
	 * environment will be used by this reader.  Otherwise, the reader will initialize and
	 * use a {@link StandardEnvironment}. All ApplicationContext implementations are
	 * EnvironmentCapable, while normal BeanFactory implementations are not.
	 * @param registry the BeanFactory to load bean definitions into,
	 * in the form of a BeanDefinitionRegistry
	 * @see #setResourceLoader
	 * @see #setEnvironment
	 */
	protected AbstractBeanDefinitionReader(BeanDefinitionRegistry registry) {
		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
		this.registry = registry;

		// Determine ResourceLoader to use.
		if (this.registry instanceof ResourceLoader) {
			this.resourceLoader = (ResourceLoader) this.registry;
		}
		else {
			this.resourceLoader = new PathMatchingResourcePatternResolver();
		}

		// Inherit Environment if possible
		if (this.registry instanceof EnvironmentCapable) {
			this.environment = ((EnvironmentCapable) this.registry).getEnvironment();
		}
		else {
			this.environment = new StandardEnvironment();
		}
	}

继续看下getValidationModeForResource(resource)方法：

    /**
	 * Determine the validation mode for the specified {@link Resource}.
	 * If no explicit validation mode has been configured, then the validation
	 * mode gets {@link #detectValidationMode detected} from the given resource.
	 * 
Override this method if you would like full control over the validation
	 * mode, even when something other than {@link #VALIDATION_AUTO} was set.
	 * @see #detectValidationMode
	 */
	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;
	}

这方法是文件格式验证模式的获取，如果手动指定了验证模式，则使用指定的验证模式，否则使用自动检查的方式

   // VALIDATION_AUTO 为 1 
	private int validationMode = VALIDATION_AUTO;

XmlBeanDefinitionReader该类默认的验证模式是自动的，如果想自定义的话，就调用

    /**
	 * Set the validation mode to use. Defaults to {@link #VALIDATION_AUTO}.
	 * 
Note that this only activates or deactivates validation itself.
	 * If you are switching validation off for schema files, you might need to
	 * activate schema namespace support explicitly: see {@link #setNamespaceAware}.
	 */
	public void setValidationMode(int validationMode) {
		this.validationMode = validationMode;
	}

继续往下走，看下自动模式的执行:

    /**
	 * Detect 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.
	 * 
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();
		}
		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);
		}
	}

    /**
	 * 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;
			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();
		}
	}

    /**
	 * Does the content contain the DTD DOCTYPE declaration?
	 */
	private boolean hasDoctype(String content) {
		return content.contains(DOCTYPE);
	}

意思简单明了，是否包含DOCTYPE，包含的话就是DTD,否则是XSD，ok，今天就这样，下篇继续！