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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.
/*
* #%L
* SciJava Common shared library for SciJava software.
* %%
* Copyright (C) 2009 - 2017 Board of Regents of the University of
* Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
* Institute of Molecular Cell Biology and Genetics, University of
* Konstanz, and KNIME GmbH.
* %%
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
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*/
package org.scijava.util;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;
import java.io.StringWriter;
import java.net.URL;
import java.util.ArrayList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
/**
* Helper class for working with XML documents.
*
* @author Curtis Rueden
*/
public class XML {
/** Path to the XML document (e.g., a file or URL). */
private final String path;
/** The parsed XML DOM. */
private final Document doc;
/** XPath evaluation mechanism. */
private final XPath xpath;
private final boolean debug =
"debug".equals(System.getProperty("scijava.log.level"));
/** Parses XML from the given file. */
public XML(final File file) throws ParserConfigurationException,
SAXException, IOException
{
this(file.getAbsolutePath(), loadXML(file));
}
/** Parses XML from the given URL. */
public XML(final URL url) throws ParserConfigurationException,
SAXException, IOException
{
this(url.getPath(), loadXML(url));
}
/** Parses XML from the given input stream. */
public XML(final InputStream in) throws ParserConfigurationException,
SAXException, IOException
{
this(null, loadXML(in));
}
/** Parses XML from the given string. */
public XML(final String s) throws ParserConfigurationException,
SAXException, IOException
{
this(null, loadXML(s));
}
/** Creates an XML object for an existing document. */
public XML(final Document doc) {
this(null, doc);
}
/** Creates an XML object for an existing document. */
public XML(final String path, final Document doc) {
this.path = path;
this.doc = doc;
// Protect against class skew: some projects find it funny to ship outdated
// xalan, causing problems due to incompatible xalan/xerces combinations.
//
// We work around that by letting the XPathFactory try with the current
// context class loader, and fall back onto its parent until it succeeds
// (because the XPathFactory will ask the context class loader to find the
// configured services, including the
// com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl).
if (debug) {
System.err.println(Types.location(XPathFactory.class));
}
XPath xp = null;
final Thread thread = Thread.currentThread();
final ClassLoader contextClassLoader = thread.getContextClassLoader();
try {
ClassLoader loader = contextClassLoader;
while (true) {
try {
xp = XPathFactory.newInstance().newXPath();
try {
// make sure that the current xalan/xerces pair can evaluate
// expressions (i.e. *not* throw NoSuchMethodErrors).
xp.evaluate("//dummy", doc);
} catch (Throwable t) {
if (debug) {
System.err.println("There was a problem with " + xp.getClass() +
" in " + Types.location(xp.getClass()) + ":");
t.printStackTrace();
}
throw new Error(t);
}
break;
}
catch (Error e) {
if (debug) e.printStackTrace();
loader = loader.getParent();
if (loader == null) throw e;
thread.setContextClassLoader(loader);
}
}
xpath = xp;
}
finally {
thread.setContextClassLoader(contextClassLoader);
}
}
// -- XML methods --
/** Gets the path to the XML document, or null if none. */
public String getPath() {
return path;
}
/** Gets the XML's DOM representation. */
public Document getDocument() {
return doc;
}
/** Obtains the CDATA identified by the given XPath expression. */
public String cdata(final String expression) {
final NodeList nodes = xpath(expression);
if (nodes == null || nodes.getLength() == 0) return null;
return cdata(nodes.item(0));
}
/** Obtains the elements identified by the given XPath expression. */
public ArrayList elements(final String expression) {
return elements(xpath(expression));
}
/** Obtains the nodes identified by the given XPath expression. */
public NodeList xpath(final String expression) {
final Object result;
try {
result = xpath.evaluate(expression, doc, XPathConstants.NODESET);
}
catch (final XPathExpressionException e) {
return null;
}
return (NodeList) result;
}
// -- Object methods --
@Override
public String toString() {
try {
return dumpXML(doc);
}
catch (final TransformerException exc) {
// NB: Return the exception stack trace as the string.
// Although this is a bad idea, I find it somehow hilarious.
final ByteArrayOutputStream out = new ByteArrayOutputStream();
exc.printStackTrace(new PrintStream(out));
return out.toString();
}
}
// -- Utility methods --
/** Gets the CData beneath the given node. */
public static String cdata(final Node item) {
final NodeList children = item.getChildNodes();
if (children == null || children.getLength() == 0) return null;
for (int i = 0; i < children.getLength(); i++) {
final Node child = children.item(i);
if (child.getNodeType() != Node.TEXT_NODE) continue;
return child.getNodeValue();
}
return null;
}
/** Gets the CData beneath the given element's specified child. */
public static String cdata(final Element el, final String child) {
NodeList children = el.getElementsByTagName(child);
if (children == null || children.getLength() == 0) return null;
return cdata(children.item(0));
}
/** Gets the element nodes from the given node list. */
public static ArrayList elements(final NodeList nodes) {
final ArrayList elements = new ArrayList<>();
if (nodes != null) {
for (int i=0; i
elements(final Element el, final String child)
{
return elements(el.getElementsByTagName(child));
}
// -- Helper methods --
/** Loads an XML document from the given file. */
private static Document loadXML(final File file)
throws ParserConfigurationException, SAXException, IOException
{
return createBuilder().parse(file.getAbsolutePath());
}
/** Loads an XML document from the given URL. */
private static Document loadXML(final URL url)
throws ParserConfigurationException, SAXException, IOException
{
final InputStream in = url.openStream();
final Document document = loadXML(in);
in.close();
return document;
}
/** Loads an XML document from the given input stream. */
protected static Document loadXML(final InputStream in)
throws ParserConfigurationException, SAXException, IOException
{
return createBuilder().parse(in);
}
/** Loads an XML document from the given input stream. */
protected static Document loadXML(final String s)
throws ParserConfigurationException, SAXException, IOException
{
return createBuilder().parse(new ByteArrayInputStream(s.getBytes()));
}
/** Creates an XML document builder. */
private static DocumentBuilder createBuilder()
throws ParserConfigurationException
{
return DocumentBuilderFactory.newInstance().newDocumentBuilder();
}
/** Converts the given DOM to a string. */
private static String dumpXML(final Document doc)
throws TransformerException
{
final Source source = new DOMSource(doc);
final StringWriter stringWriter = new StringWriter();
final Result result = new StreamResult(stringWriter);
final TransformerFactory factory = TransformerFactory.newInstance();
final Transformer transformer = factory.newTransformer();
transformer.transform(source, result);
return stringWriter.getBuffer().toString();
}
}