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;
}