top-10-reasons-to-use-spring-framework-1.jpg
我们上一篇文章最后调用到 `org.springframework.beans.factory.xml. XmlBeanDefinitionReader#doLoadDocument(…)

` 方法,该方法主要代码如下:

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protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
//getValidationModeForResource是数据验证模型
return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
getValidationModeForResource(resource), isNamespaceAware());
}

我们这篇文章主要以 #getValidationModeForResource(...) 方法作为切入,来分析一下验证模型的主要方法,关于spring中的数据验证、绑定等内容我们在后面文章一点点的来挖掘

1.getValidationModeForResource

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/**
* 禁止只用验证模型
* Indicates that the validation should be disabled.
*/
public static final int VALIDATION_NONE = XmlValidationModeDetector.VALIDATION_NONE;
/**
* 使用自动检测验证模型
* Indicates that the validation mode should be detected automatically.
*/
public static final int VALIDATION_AUTO = XmlValidationModeDetector.VALIDATION_AUTO;
/**
* 使用DTD验证模型
* Indicates that DTD validation should be used.
*/
public static final int VALIDATION_DTD = XmlValidationModeDetector.VALIDATION_DTD;
/**
* 使用XSD验证模型
* Indicates that XSD validation should be used.
*/
public static final int VALIDATION_XSD = XmlValidationModeDetector.VALIDATION_XSD;
/**
* 确定当前 resource资源需要的验证模型 默认自动模式
* 如果显式的配置了验证模型,则用配置的,如果没有则从Resource中来获取
* 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.
* <p>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) {
// <1> 获取指定的验证模式
int validationModeToUse = getValidationMode();
// <2> 如果有指定的模式 则直接返回,
if (validationModeToUse != VALIDATION_AUTO) {
return validationModeToUse;
}
//<3> 没有指定的 那么通resource中去获取
int detectedMode = detectValidationMode(resource);
if (detectedMode != VALIDATION_AUTO) {
return detectedMode;
}
// <4> 若以上都不满足则使用XSD模式
// 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;
}

对上述代码我们做简单分析

  • <1>处调用 #getValidationMode() 方法来获取指定的验证模式 ,这里的 validationMode 如果是外部手动设置的,那么就直接返回,
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/**
* Set the validation mode to use. Defaults to {@link #VALIDATION_AUTO}.
* <p>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;
}
/**
* Return the validation mode to use.
*/
public int getValidationMode() {
return this.validationMode;
}
  • <3>处调用 #detectValidationMode() 方法来自动获取验证模型,代码如下:
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/**
* 进行自动检测指定的XML用那种检测模型
* 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.
* <p>Override this method if you would like to customize resolution
* of the {@link #VALIDATION_AUTO} mode.
*/
protected int detectValidationMode(Resource resource) {
// <1> 资源是否打开
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 {
////<2> 调用XmlValidationModeDetector 中的真实实现 传入 inputStream
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);
}
}

2.detectValidationMode

上面 <3>处调用了 #detectValidationMode() 方法,这里 validationModeDetector 对象是类中的一个不可变成员变量 定义如下:

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private final XmlValidationModeDetector validationModeDetector = new XmlValidationModeDetector();

#detectValidationMode() 方法的具体实现如下:

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/**
* 通过指定的 inputStream 来检测 XML 中的验证模型
* 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 {
//<1> 通过 BufferedReader 读取inputStream
// Peek into the file to look for DOCTYPE.
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
try {
//<2> 是否是DTD验证模式 ,默认否
boolean isDtdValidated = false;
String content;
// <3> 逐行读取内容
while ((content = reader.readLine()) != null) {
content = consumeCommentTokens(content);
// <4> 如果是注释或者为空这跳过
if (this.inComment || !StringUtils.hasText(content)) {
continue;
}
// <5> 校验是否包含 DOCTYPE 若包含则为DTD模式
if (hasDoctype(content)) {
isDtdValidated = true;
break;
}
// <6> 校验是否是打开的标签, 如果一行有 < 并且后面跟着是字母,那么返回
if (hasOpeningTag(content)) {
// End of meaningful data...
break;
}
}
// 确定解析方式
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 {
//关闭流
reader.close();
}
}
  • 上述代码中<5>处校验是否包含了 DOCTYPE 字符,具体代码如下:
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/**
* The token in a XML document that declares the DTD to use for validation
* and thus that DTD validation is being used.
*/
private static final String DOCTYPE = "DOCTYPE";
/**
* 判断是否包含 DOCTYPE
* Does the content contain the DTD DOCTYPE declaration?
*/
private boolean hasDoctype(String content) {
return content.contains(DOCTYPE);
}
  • <6>处进行了标签的打开判断,代码如下:
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/**
* Does the supplied content contain an XML opening tag. If the parse state is currently
* in an XML comment then this method always returns false. It is expected that all comment
* tokens will have consumed for the supplied content before passing the remainder to this method.
*/
private boolean hasOpeningTag(String content) {
if (this.inComment) {
return false;
}
int openTagIndex = content.indexOf('<'); // 获取字符中 < 的索引
return (openTagIndex > -1 // 存在 <
&& (content.length() > openTagIndex + 1) // 并且后面还有内容
&&Character.isLetter(content.charAt(openTagIndex + 1)));//后面必须是字母
}
  • 如果抛出异常时 CharConversionException 则默认设置为自动 VALIDATION_AUTO

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