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Common, generally useful utilities
package org.fcrepo.utilities.xml;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringReader;
import java.io.StringWriter;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.fcrepo.utilities.XmlTransformUtility;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
/**
* Helpers for doing DOM parsing and manipulations.
*
* Ported from the State and University Library project sbutils.
*/
public class DOM {
private static final Logger log = LoggerFactory.getLogger(DOM.class);
public static final String XML_HEADER =
"";
private static final XPathSelectorImpl selector =
new XPathSelectorImpl(null, 50);
/**
* Extracts all textual and CDATA content from the given node and its
* children.
*
* @param node the node to get the content from.
* @return the textual content of node.
*/
public static String getElementNodeValue(Node node) {
StringWriter sw = new StringWriter(2000);
if (node.getNodeType() == Node.ELEMENT_NODE) {
NodeList all = node.getChildNodes();
for (int i = 0; i < all.getLength(); i++) {
if (all.item(i).getNodeType() == Node.TEXT_NODE ||
all.item(i).getNodeType() == Node.CDATA_SECTION_NODE) {
// TODO: Check if we exceed the limit for getNodeValue
sw.append(all.item(i).getNodeValue());
}
}
}
return sw.toString();
}
/* **************************************** */
/**
* Parses an XML document from a String to a DOM.
*
* @param xmlString a String containing an XML document.
* @param namespaceAware if {@code true} the parsed DOM will reflect any
* XML namespaces declared in the document
* @return The document in a DOM or {@code null} on errors.
*/
public static Document stringToDOM(String xmlString,
boolean namespaceAware) {
try {
InputSource in = new InputSource();
in.setCharacterStream(new StringReader(xmlString));
DocumentBuilderFactory dbFact = DocumentBuilderFactory.newInstance();
dbFact.setNamespaceAware(namespaceAware);
return dbFact.newDocumentBuilder().parse(in);
} catch (IOException e) {
log.warn("I/O error when parsing XML :" + e.getMessage() + "\n"
+ xmlString, e);
} catch (SAXException e) {
log.warn("Parse error when parsing XML :" + e.getMessage() + "\n"
+ xmlString, e);
} catch (ParserConfigurationException e) {
log.warn("Parser configuration error when parsing XML :"
+ e.getMessage() + "\n"
+ xmlString, e);
}
return null;
}
/**
* Parses an XML document from a String disregarding namespaces
*
* @param xmlString a String containing an XML document.
* @return The document in a DOM or {@code null} on errors.
*/
public static Document stringToDOM(String xmlString) {
return stringToDOM(xmlString, false);
}
/**
* Parses a XML document from a stream to a DOM or return
* {@code null} on error.
*
* @param xmlStream a stream containing an XML document.
* @param namespaceAware if {@code true} the constructed DOM will reflect
* the namespaces declared in the XML document
* @return The document in a DOM or {@code null} in case of errors
*/
public static Document streamToDOM(InputStream xmlStream,
boolean namespaceAware) {
try {
DocumentBuilderFactory dbFact = DocumentBuilderFactory.newInstance();
dbFact.setNamespaceAware(namespaceAware);
return dbFact.newDocumentBuilder().parse(xmlStream);
} catch (IOException e) {
log.warn("I/O error when parsing stream :" + e.getMessage(), e);
} catch (SAXException e) {
log.warn("Parse error when parsing stream :" + e.getMessage(), e);
} catch (ParserConfigurationException e) {
log.warn("Parser configuration error when parsing XML stream: "
+ e.getMessage(), e);
}
return null;
}
/**
* Parses a XML document from a stream to a DOM disregarding namespaces.
* Returns {@code null} on error.
*
* @param xmlStream a stream containing an XML document.
* @return The document in a DOM or {@code null} in case of errors
*/
public static Document streamToDOM(InputStream xmlStream) {
return streamToDOM(xmlStream, false);
}
/**
* Convert the given DOM to an UTF-8 XML String.
*
* @param dom the Document to convert.
* @return the dom as an XML String.
* @throws TransformerException if the dom could not be converted.
*/
public static String domToString(Node dom) throws Exception {
return domToString(dom, false);
}
/**
* Convert the given DOM to an UTF-8 XML String.
*
* @param dom the Document to convert.
* @param withXmlDeclaration if trye, an XML-declaration is prepended.
* @return the dom as an XML String.
* @throws TransformerException if the dom could not be converted.
*/
// TODO: Consider optimizing this with ThreadLocal Transformers
public static String domToString(Node dom, boolean withXmlDeclaration)
throws Exception {
Transformer t = XmlTransformUtility.getTransformer();
t.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
if (withXmlDeclaration) {
t.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
} else {
t.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
}
t.setOutputProperty(OutputKeys.METHOD, "xml");
/* Transformer */
StringWriter sw = new StringWriter();
t.transform(new DOMSource(dom), new StreamResult(sw));
return sw.toString();
}
/**
* Create a new {@link XPathSelector} instance with a given namespace
* mapping. The arguments are parsed as
* {@code prefix1, uri1, prefix2, uri2, ...}.
*
* If you want to apply XPath expressions without namespaces use the static
* {@code select*} methods directly on the {@code DOM} class.
*
* Note that if you want to apply XPath selections on a DOM constructed from
* either {@link DOM#streamToDOM(InputStream, boolean)} or
* {@link DOM#stringToDOM(String, boolean)} you must pass
* {@code namespaceAware=true} as the boolean argument. Namespaced
* selections will fail on a DOM constructed without namespaces.
*
* @param nsContext prefix, uri pairs
* @return a newly allocated {@link XPathSelector}
* @throws IllegalArgumentException if an uneven number of arguments are
* passed
*/
public static XPathSelector createXPathSelector(String... nsContext) {
return new XPathSelectorImpl(
new DefaultNamespaceContext(null, nsContext), 50);
}
/**
* Extract an integer value from {@code node} or return {@code defaultValue}
* if it is not found.
*
* @param node the node with the wanted attribute.
* @param xpath the XPath to extract.
* @param defaultValue the default value.
* @return the value of the path, if existing, else
* defaultValue
*/
public static Integer selectInteger(Node node, String xpath, Integer defaultValue) {
return selector.selectInteger(node, xpath, defaultValue);
}
/**
* Extract an integer value from {@code node} or return {@code null} if it
* is not found
*
* @param node the node with the wanted attribute.
* @param xpath the XPath to extract.
* @return the value of the path or {@code null}
*/
public static Integer selectInteger(Node node, String xpath) {
return selector.selectInteger(node, xpath);
}
/**
* Extract a double precision floating point value from {@code node} or
* return {@code defaultValue} if it is not found
*
* @param node the node with the wanted attribute.
* @param xpath the XPath to extract.
* @param defaultValue the default value.
* @return the value of the path, if existing, else
* defaultValue
*/
public static Double selectDouble(Node node,
String xpath, Double defaultValue) {
return selector.selectDouble(node, xpath, defaultValue);
}
/**
* Extract a double precision floating point value from {@code node} or
* return {@code null} if it is not found
*
* @param node the node with the wanted attribute.
* @param xpath the XPath to extract.
* @return the value of the path or {@code null}
*/
public static Double selectDouble(Node node, String xpath) {
return selector.selectDouble(node, xpath);
}
/**
* Extract a boolean value from {@code node} or return {@code defaultValue}
* if there is no boolean value at {@code xpath}
*
* @param node the node with the wanted attribute.
* @param xpath the path to extract.
* @param defaultValue the default value.
* @return the value of the path, if existing, else
* {@code defaultValue}
*/
public static Boolean selectBoolean(Node node,
String xpath, Boolean defaultValue) {
return selector.selectBoolean(node, xpath, defaultValue);
}
/**
* Extract a boolean value from {@code node} or return {@code false}
* if there is no boolean value at {@code xpath}
*
* @param node the node with the wanted attribute.
* @param xpath the path to extract.
* @return the value of the path, if existing, else
* {@code false}
*/
public static Boolean selectBoolean(Node node, String xpath) {
return selector.selectBoolean(node, xpath);
}
/**
* Extract the given value from the node as a String or if the value cannot
* be extracted, {@code defaultValue} is returned.
*
* Example: To get the value of the attribute "foo" in the node, specify
* "@foo" as the path.
*
* Note: This method does not handle namespaces explicitely.
*
* @param node the node with the wanted attribute
* @param xpath the XPath to extract.
* @param defaultValue the default value
* @return the value of the path, if existing, else
* {@code defaultValue}
*/
public static String selectString(Node node, String xpath, String defaultValue) {
return selector.selectString(node, xpath, defaultValue);
}
/**
* Extract the given value from the node as a String or if the value cannot
* be extracted, the empty string is returned
*
* Example: To get the value of the attribute "foo" in the node, specify
* "@foo" as the path.
*
* Note: This method does not handle namespaces explicitely.
*
* @param node the node with the wanted attribute
* @param xpath the XPath to extract
* @return the value of the path, if existing, else
* the empty string
*/
public static String selectString(Node node, String xpath) {
return selector.selectString(node, xpath);
}
/**
* Select the {@link NodeList} with the given XPath.
*
* Note: This is a convenience method that logs exceptions instead of
* throwing them.
*
* @param node the root document.
* @param xpath the xpath for the Node list.
* @return the NodeList requested or an empty NodeList if unattainable
*/
public static NodeList selectNodeList(Node node, String xpath) {
return selector.selectNodeList(node, xpath);
}
/**
* Select the Node with the given XPath.
*
* Note: This is a convenience method that logs exceptions instead of
* throwing them.
*
* @param dom the root document.
* @param xpath the xpath for the node.
* @return the Node or null if unattainable.
*/
public static Node selectNode(Node dom, String xpath) {
return selector.selectNode(dom, xpath);
}
/**
* Package private method to clear the expression cache
* - used for unit testing
*/
static void clearXPathCache() {
selector.clearCache();
}
}