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關于在DOM4J在讀取XML文件時，解釋DTD的問題[轉自javaeye]

近日在使用 DOM4J 的時候，遇到一個問題，現在有兩個解決方法，先記下來，以便日后使用。

問題：對一個 XML 文件進行讀寫操作，但是發現當文件存在的時候，使用DOM4J讀進來的時候，生成的 Document 對象會根據 DTD 里的定義，追加了一些 default 屬性（實際不需要）。而且在讀取的時間被延長。

有一個 XML 文件如下：

xml 代碼

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
....
</beans>

使用 DOM4J 的讀取文件的一般性寫法：

java 代碼

SAXReader reader = new SAXReader(false);
document = reader.read(file);
root = document.getRootElement();

對象 document 里的節點會被自動追加 DTD 里的定義的 default 屬性，只有新增加的節點不受影響，如下。而且，如果文件的操作時間被延長。

xml 代碼

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans default-lazy-init="false" default-autowire="no" default-dependency-check="none">
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase" lazy-init="default" autowire="default" dependency-check="default"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase" lazy-init="default" autowire="default" dependency-check="default"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase" lazy-init="default" autowire="default" dependency-check="default"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase" lazy-init="default" autowire="default" dependency-check="default"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase" lazy-init="default" autowire="default" dependency-check="default"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase" lazy-init="default" autowire="default" dependency-check="default"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase" lazy-init="default" autowire="default" dependency-check="default"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase"/>
<bean id="OperateXmlByDom4jTestCase" class="test.OperateXmlByDom4jTestCase"/>
</beans>

為了不讓生成我們不需要的 default 屬性和縮短文件的操作時間，我們可以調用 SAXReader.setFeature 方法來改變 DOM4J 的行為，片斷代碼如下：

java 代碼

// http://apache.org/xml/features/nonvalidating/load-external-dtd"
saxReader.setFeature(
Constants.XERCES_FEATURE_PREFIX + Constants.LOAD_EXTERNAL_DTD_FEATURE,
false);

關于更多的 Feature 請參考 com.sun.org.apache.xerces.internal.impl.Constants

以下為片斷代碼：

java 代碼

// xerces features
/** Xerces features prefix ("http://apache.org/xml/features/"). */
public static final String XERCES_FEATURE_PREFIX = "http://apache.org/xml/features/";
/** Schema validation feature ("validation/schema"). */
public static final String SCHEMA_VALIDATION_FEATURE = "validation/schema";
/** Expose schema normalized values */
public static final String SCHEMA_NORMALIZED_VALUE = "validation/schema/normalized-value";
/** Send schema default value via characters() */
public static final String SCHEMA_ELEMENT_DEFAULT = "validation/schema/element-default";
/** Schema full constraint checking ("validation/schema-full-checking"). */
public static final String SCHEMA_FULL_CHECKING = "validation/schema-full-checking";
/** Augment Post-Schema-Validation-Infoset */
public static final String SCHEMA_AUGMENT_PSVI = "validation/schema/augment-psvi";
/** Dynamic validation feature ("validation/dynamic"). */
public static final String DYNAMIC_VALIDATION_FEATURE = "validation/dynamic";
/** Warn on duplicate attribute declaration feature ("validation/warn-on-duplicate-attdef"). */
public static final String WARN_ON_DUPLICATE_ATTDEF_FEATURE = "validation/warn-on-duplicate-attdef";
/** Warn on undeclared element feature ("validation/warn-on-undeclared-elemdef"). */
public static final String WARN_ON_UNDECLARED_ELEMDEF_FEATURE = "validation/warn-on-undeclared-elemdef";
/** Warn on duplicate entity declaration feature ("warn-on-duplicate-entitydef"). */
public static final String WARN_ON_DUPLICATE_ENTITYDEF_FEATURE = "warn-on-duplicate-entitydef";
/** Allow Java encoding names feature ("allow-java-encodings"). */
public static final String ALLOW_JAVA_ENCODINGS_FEATURE = "allow-java-encodings";
/** Disallow DOCTYPE declaration feature ("disallow-doctype-decl"). */
public static final String DISALLOW_DOCTYPE_DECL_FEATURE = "disallow-doctype-decl";
/** Continue after fatal error feature ("continue-after-fatal-error"). */
public static final String CONTINUE_AFTER_FATAL_ERROR_FEATURE = "continue-after-fatal-error";
/** Load dtd grammar when nonvalidating feature ("nonvalidating/load-dtd-grammar"). */
public static final String LOAD_DTD_GRAMMAR_FEATURE = "nonvalidating/load-dtd-grammar";
/** Load external dtd when nonvalidating feature ("nonvalidating/load-external-dtd"). */
public static final String LOAD_EXTERNAL_DTD_FEATURE = "nonvalidating/load-external-dtd";
/** Defer node expansion feature ("dom/defer-node-expansion"). */
public static final String DEFER_NODE_EXPANSION_FEATURE = "dom/defer-node-expansion";
/** Create entity reference nodes feature ("dom/create-entity-ref-nodes"). */
public static final String CREATE_ENTITY_REF_NODES_FEATURE = "dom/create-entity-ref-nodes";
/** Include ignorable whitespace feature ("dom/include-ignorable-whitespace"). */
public static final String INCLUDE_IGNORABLE_WHITESPACE = "dom/include-ignorable-whitespace";
/** Default attribute values feature ("validation/default-attribute-values"). */
public static final String DEFAULT_ATTRIBUTE_VALUES_FEATURE = "validation/default-attribute-values";
/** Validate content models feature ("validation/validate-content-models"). */
public static final String VALIDATE_CONTENT_MODELS_FEATURE = "validation/validate-content-models";
/** Validate datatypes feature ("validation/validate-datatypes"). */
public static final String VALIDATE_DATATYPES_FEATURE = "validation/validate-datatypes";
/** Notify character references feature (scanner/notify-char-refs"). */
public static final String NOTIFY_CHAR_REFS_FEATURE = "scanner/notify-char-refs";
/** Notify built-in (&, etc.) references feature (scanner/notify-builtin-refs"). */
public static final String NOTIFY_BUILTIN_REFS_FEATURE = "scanner/notify-builtin-refs";
/** Standard URI conformant feature ("standard-uri-conformant"). */
public static final String STANDARD_URI_CONFORMANT_FEATURE = "standard-uri-conformant";
/** Internal performance related feature:
* false - the parser settings (features/properties) have not changed between 2 parses
* true - the parser settings have changed between 2 parses
* NOTE: this feature should only be set by the parser configuration.
*/
public static final String PARSER_SETTINGS = "internal/parser-settings";
/** Feature to make XML Processor XInclude Aware */
public static final String XINCLUDE_AWARE = "xinclude-aware";
/** Ignore xsi:schemaLocation and xsi:noNamespaceSchemaLocation. */
public static final String IGNORE_SCHEMA_LOCATION_HINTS = "validation/schema/ignore-schema-location-hints";
/**
* When true, the schema processor will change characters events
* to ignorableWhitespaces events, when characters are expected to
* only contain ignorable whitespaces.
*/
public static final String CHANGE_IGNORABLE_CHARACTERS_INTO_IGNORABLE_WHITESPACES =
"validation/change-ignorable-characters-into-ignorable-whitespaces";

除通過上面的 SAXReader.setFeature 文件之外，我們還可以通過自己的 EntityResolver 來解決這個問題。

PS：這個方法是從凝香小筑的BLOG里的一編主題是：Do not resolve DTD files when dom4j read xml file 的文章里看到的。地址：http://blog.csdn.net/lessoft/archive/2007/06/20/1659579.aspx

代碼片斷如下：

java 代碼

saxReader.setEntityResolver(new EntityResolver() {
String emptyDtd = "";
ByteArrayInputStream bytels = new ByteArrayInputStream(emptyDtd.getBytes());
public InputSource resolveEntity(String publicId, String systemId)
throws SAXException, IOException {
return new InputSource(bytels);
}
});

完整的代碼如下：

java 代碼

package test;
import java.io.BufferedWriter;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import junit.framework.TestCase;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import org.dom4j.tree.DefaultDocumentType;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import com.sun.org.apache.xerces.internal.impl.Constants;
/**
* A test case class for read and writer a xml file by Dom4j.
* @author X.F.Yang [2007/07/03]
* @version 1.0
*/
public class OperateXmlByDom4jTestCase extends TestCase {
/**
* Default way to read and writer a xml file by Dom4j.
* @throws Exception
*/
public void testWriteXml() throws Exception {
XmlFileOperation operation = new XmlFileOperation();
operation.writer(new SAXReaderWrapper() {
public void operation(SAXReader saxReader) throws Exception {
// Nothing to do.
}
});
}
/**
* Do not resolve DTD files when dom4j read xml file via the set feature.
* @throws Exception
*/
public void testWriteXmlSetFeature() throws Exception {
XmlFileOperation operation = new XmlFileOperation();
operation.writer(new SAXReaderWrapper() {
public void operation(SAXReader saxReader) throws Exception {
// http://apache.org/xml/features/nonvalidating/load-external-dtd"
saxReader.setFeature(
Constants.XERCES_FEATURE_PREFIX + Constants.LOAD_EXTERNAL_DTD_FEATURE,
false);
}
});
}
/**
* Do not resolve DTD files when dom4j read xml file via implement {@link EntityResolver}.
* @throws Exception
*/
public void testWriteXmlEntityResolver() throws Exception {
XmlFileOperation operation = new XmlFileOperation();
operation.writer(new SAXReaderWrapper() {
public void operation(SAXReader saxReader) throws Exception {
saxReader.setEntityResolver(new EntityResolver() {
String emptyDtd = "";
ByteArrayInputStream bytels = new ByteArrayInputStream(emptyDtd.getBytes());
public InputSource resolveEntity(String publicId,
String systemId) throws SAXException, IOException {
return new InputSource(bytels);
}
});
}
});
}
/** */
protected interface SAXReaderWrapper {
/** operation {@link SAXReader} */
void operation(SAXReader saxReader) throws Exception;
}
/**
* when the target file was existed, read and append the new element.
* else, create a new xml file and add the new element.
*/
protected class XmlFileOperation {
/** target file */
private File file;
public XmlFileOperation() {
// target file
file = new File("d:""spring.xml");
}
/**
* Write xml file
* @param wrapper
* @throws Exception
* @see {@link SAXReaderWrapper}
*/
public void writer(SAXReaderWrapper wrapper) throws Exception {
try {
Document document = null;
Element root = null;
// read the xml file if target file was existed
if (file.exists()) {
SAXReader reader = new SAXReader(false);
wrapper.operation(reader);
document = reader.read(file);
root = document.getRootElement();
// if the target file was not existed, create a new one
} else {
document = DocumentHelper.createDocument();
document.setDocType(new DefaultDocumentType("beans",
"-//SPRING//DTD BEAN//EN",
"http://www.springframework.org/dtd/spring-beans.dtd"));
root = document.addElement("beans");
}
// create the element under the root element
root.addElement("bean")
.addAttribute("id", "OperateXmlByDom4jTestCase")
.addAttribute("class", "test.OperateXmlByDom4jTestCase");
// writer the document
writer(document);
} catch (Exception e) {
e.printStackTrace();
throw e;
}
}
protected void writer(Document document) throws Exception {
XMLWriter xmlWriter = null;
try {
final OutputFormat format = OutputFormat.createPrettyPrint();
xmlWriter = new XMLWriter(new BufferedWriter(new FileWriter(file)), format);
xmlWriter.write(document);
} finally {
if (null != xmlWriter) {
xmlWriter.flush();
xmlWriter.close();
}
}
}
}
}

posted on 2008-07-22 10:03 蘆葦閱讀(2312) 評論(0) 編輯收藏所屬分類: Spring 、XML

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