我們上一篇文章最后呼叫到 `org.springframework.beans.factory.xml. XmlBeanDefinitionReader#doLoadDocument(...)
` 方法，該方法主要代碼如下：
protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
//getValidationModeForResource是資料驗證模型
return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
getValidationModeForResource(resource), isNamespaceAware());
}
我們這篇文章主要以 #getValidationModeForResource(...) 方法作為切入，來分析一下驗證模型的主要方法，關于spring中的資料驗證、系結等內容我們在后面文章一點點的來挖掘
1.getValidationModeForResource
/**
* 禁止只用驗證模型
* Indicates that the validation should be disabled.
*/
public static final int VALIDATION_NONE = XmlValidationModeDetector.VALIDATION_NONE;
/**
* 使用自動檢測驗證模型
* Indicates that the validation mode should be detected automatically.
*/
public static final int VALIDATION_AUTO = XmlValidationModeDetector.VALIDATION_AUTO;
/**
* 使用DTD驗證模型
* Indicates that DTD validation should be used.
*/
public static final int VALIDATION_DTD = XmlValidationModeDetector.VALIDATION_DTD;
/**
* 使用XSD驗證模型
* Indicates that XSD validation should be used.
*/
public static final int VALIDATION_XSD = XmlValidationModeDetector.VALIDATION_XSD;
/**
* 確定當前 resource資源需要的驗證模型 默認自動模式
* 如果顯式的配置了驗證模型，則用配置的，如果沒有則從Resource中來獲取
* 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> 獲取指定的驗證模式
int validationModeToUse = getValidationMode();
// <2> 如果有指定的模式 則直接回傳，
if (validationModeToUse != VALIDATION_AUTO) {
return validationModeToUse;
}
//<3> 沒有指定的 那么通resource中去獲取
int detectedMode = detectValidationMode(resource);
if (detectedMode != VALIDATION_AUTO) {
return detectedMode;
}
// <4> 若以上都不滿足則使用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;
}
對上述代碼我們做簡單分析
- <1>處呼叫
#getValidationMode()方法來獲取指定的驗證模式 ，這里的validationMode如果是外部手動設定的，那么就直接回傳，
/**
* 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>處呼叫
#detectValidationMode()方法來自動獲取驗證模型，代碼如下：
/**
* 進行自動檢測指定的XML用那種檢測模型
* 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> 資源是否打開
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> 呼叫XmlValidationModeDetector 中的真實實作 傳入 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>處呼叫了 #detectValidationMode() 方法，這里 validationModeDetector 物件是類中的一個不可變成員變數 定義如下：
private final XmlValidationModeDetector validationModeDetector = new XmlValidationModeDetector();
#detectValidationMode() 方法的具體實作如下：
/**
* 通過指定的 inputStream 來檢測 XML 中的驗證模型
* 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> 通過 BufferedReader 讀取inputStream
// Peek into the file to look for DOCTYPE.
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
try {
//<2> 是否是DTD驗證模式 ，默認否
boolean isDtdValidated = false;
String content;
// <3> 逐行讀取內容
while ((content = reader.readLine()) != null) {
content = consumeCommentTokens(content);
// <4> 如果是注釋或者為空這跳過
if (this.inComment || !StringUtils.hasText(content)) {
continue;
}
// <5> 校驗是否包含 DOCTYPE 若包含則為DTD模式
if (hasDoctype(content)) {
isDtdValidated = true;
break;
}
// <6> 校驗是否是打開的標簽， 如果一行有 < 并且后面跟著是字母，那么回傳
if (hasOpeningTag(content)) {
// End of meaningful data...
break;
}
}
// 確定決議方式
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 {
//關閉流
reader.close();
}
}
- 上述代碼中<5>處校驗是否包含了
DOCTYPE字符，具體代碼如下：
/**
* 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";
/**
* 判斷是否包含 DOCTYPE
* Does the content contain the DTD DOCTYPE declaration?
*/
private boolean hasDoctype(String content) {
return content.contains(DOCTYPE);
}
- <6>處進行了標簽的打開判斷，代碼如下：
/**
* 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('<'); // 獲取字符中 < 的索引
return (openTagIndex > -1 // 存在 <
&& (content.length() > openTagIndex + 1) // 并且后面還有內容
&&Character.isLetter(content.charAt(openTagIndex + 1)));//后面必須是字母
}
- 如果拋出例外時
CharConversionException則默認設定為自動VALIDATION_AUTO
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