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/*******************************************************************************
* Copyright (c) 2006, 2008 IBM Corporation and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.internal.transforms.xslt;
import java.io.*;
import java.lang.ref.SoftReference;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import javax.xml.transform.*;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.stream.StreamResult;
import org.eclipse.equinox.internal.transforms.Pipe;
import org.eclipse.osgi.framework.log.FrameworkLog;
import org.eclipse.osgi.framework.log.FrameworkLogEntry;
import org.osgi.framework.FrameworkEvent;
import org.osgi.util.tracker.ServiceTracker;
import org.xml.sax.*;
import org.xml.sax.helpers.XMLReaderFactory;
/**
* Implements the XSLT stream transformer.
* This class is capable of taking a source stream and an URL and applying the contents of the URL as a XSLT transform to the contents of the stream.
*/
public class XSLTStreamTransformer {
/**
* Subclass of Pipe that is able to apply XSLT Transformers to the original input stream.
* All handling of XML is done with validation and entity resolution disabled to improve performance and prevent undesired network access.
*/
class XSLTPipe extends Pipe {
private Transformer transformer;
public XSLTPipe(InputStream original, Transformer transformer) throws IOException {
super(original);
this.transformer = transformer;
}
@Override
protected void pipeInput(InputStream original, OutputStream result) throws IOException {
try {
InputSource streamSource = new InputSource(original);
XMLReader reader = XMLReaderFactory.createXMLReader();
if (resolver != null)
reader.setEntityResolver(resolver);
else
reader.setFeature("http://xml.org/sax/features/validation", //$NON-NLS-1$
false);
SAXSource saxSource = new SAXSource(reader, streamSource);
transformer.transform(saxSource, new StreamResult(result));
} catch (TransformerException e) {
log(FrameworkEvent.ERROR, "Could not perform transform.", e); //$NON-NLS-1$
throw new IOException(e.getMessage());
} catch (SAXException e) {
log(FrameworkEvent.ERROR, "Problem parsing transform.", e); //$NON-NLS-1$
throw new IOException(e.getMessage());
}
}
}
/**
* The dummy entity resolver which returns empty content for all external entity requests.
*/
protected EntityResolver resolver = new EntityResolver() {
@Override
public InputSource resolveEntity(String publicId, String systemId) {
// don't validate external entities - too expensive
return new InputSource(new StringReader("")); //$NON-NLS-1$
}
};
/**
* Tracks the logging service.
*/
private ServiceTracker<FrameworkLog, FrameworkLog> logTracker;
/**
* A map containing compiled XSLT transformations.
* These transforms are held by soft references so that we don't bloat memory for this purpose.
* After startup these transforms are of little use.
*/
private static final Map<URL, SoftReference<Templates>> templateMap = new HashMap<>();
/**
* Create a new instance of this transformer.
*
* @param logTracker the log service
*/
public XSLTStreamTransformer(ServiceTracker<FrameworkLog, FrameworkLog> logTracker) {
this.logTracker = logTracker;
}
/**
* Implements the StreamTransformer.getInput(InputStream, URL) method.
* @param inputStream the original stream
* @param transformerUrl the transformer URL. This should be an URL pointing to an XSLT transform.
* @return the transformed input stream
* @throws IOException thrown if there is an issue reading from the original stream or applying the transform.
*/
public InputStream getInputStream(InputStream inputStream, URL transformerUrl) throws IOException {
Templates template = getTemplate(transformerUrl);
if (template != null) {
Transformer transformer = null;
try {
transformer = template.newTransformer();
XSLTPipe pipe = new XSLTPipe(inputStream, transformer);
return pipe.getPipedInputStream();
} catch (TransformerConfigurationException e) {
log(FrameworkEvent.ERROR, "Could not perform transform.", e); //$NON-NLS-1$
}
}
return null;
}
/**
* Get a cached template for the provided XSLT template URL.
* If the cached entry for this URL does not exist it will be created.
* @param transformerURL the XSLT template URL.
* @return the template
*/
private synchronized Templates getTemplate(URL transformerURL) {
Templates templates = null;
SoftReference<Templates> templatesRef = templateMap.get(transformerURL);
if (templatesRef != null) {
templates = templatesRef.get();
}
if (templates != null)
return templates;
try {
InputStream xsltStream = transformerURL.openStream();
TransformerFactory tFactory = null;
try {
tFactory = TransformerFactory.newInstance();
InputSource inputSource = new InputSource(xsltStream);
XMLReader reader = XMLReaderFactory.createXMLReader();
if (resolver != null)
reader.setEntityResolver(resolver);
else
reader.setFeature("http://xml.org/sax/features/validation", //$NON-NLS-1$
false);
SAXSource xsltSource = new SAXSource(reader, inputSource);
try {
templatesRef = new SoftReference<>(templates = tFactory.newTemplates(xsltSource));
templateMap.put(transformerURL, templatesRef);
} catch (Exception e) {
// can't create the template. May be an IO
// exception from the source or perhaps a badly
// formed XSLT. We shouldn't fail in this case.
log(FrameworkEvent.WARNING, "Could not create transform template: " //$NON-NLS-1$
+ transformerURL.toString(), e);
}
} catch (TransformerFactoryConfigurationError e) {
// we can proceed without a factory
log(FrameworkEvent.WARNING, "Could not create transformer factory. No transforms will be invoked.", //$NON-NLS-1$
e);
} catch (SAXException e) {
// we can proceed without a reader
log(FrameworkEvent.WARNING, "Could not create XML reader. No transforms will be invoked.", //$NON-NLS-1$
e);
}
} catch (IOException e) {
log(FrameworkEvent.WARNING, "General IO Exception creating templates.", e); //$NON-NLS-1$
}
return templates;
}
void log(int severity, String msg, Throwable t) {
FrameworkLog log = logTracker.getService();
if (log == null) {
if (msg != null)
System.err.println(msg);
if (t != null)
t.printStackTrace();
return;
}
FrameworkLogEntry entry = new FrameworkLogEntry("org.eclipse.equinox.transforms.xslt", severity, 0, msg, 0, t, //$NON-NLS-1$
null);
log.log(entry);
}
}
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