org.apache.poi.util.SAXHelper Maven / Gradle / Ivy
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contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
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http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
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See the License for the specific language governing permissions and
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package org.apache.poi.util;
import java.io.IOException;
import java.io.StringReader;
import java.lang.reflect.Method;
import javax.xml.XMLConstants;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
/**
* Provides handy methods for working with SAX parsers and readers
*/
public final class SAXHelper {
private static POILogger logger = POILogFactory.getLogger(SAXHelper.class);
private SAXHelper() {}
/**
* Creates a new SAX XMLReader, with sensible defaults
*/
public static synchronized XMLReader newXMLReader() throws SAXException, ParserConfigurationException {
XMLReader xmlReader = saxFactory.newSAXParser().getXMLReader();
xmlReader.setEntityResolver(IGNORING_ENTITY_RESOLVER);
trySetSAXFeature(xmlReader, XMLConstants.FEATURE_SECURE_PROCESSING, true);
trySetXercesSecurityManager(xmlReader);
return xmlReader;
}
static final EntityResolver IGNORING_ENTITY_RESOLVER = new EntityResolver() {
@Override
public InputSource resolveEntity(String publicId, String systemId)
throws SAXException, IOException {
return new InputSource(new StringReader(""));
}
};
private static final SAXParserFactory saxFactory;
static {
saxFactory = SAXParserFactory.newInstance();
saxFactory.setValidating(false);
saxFactory.setNamespaceAware(true);
}
private static void trySetSAXFeature(XMLReader xmlReader, String feature, boolean enabled) {
try {
xmlReader.setFeature(feature, enabled);
} catch (Exception e) {
logger.log(POILogger.WARN, "SAX Feature unsupported", feature, e);
} catch (AbstractMethodError ame) {
logger.log(POILogger.WARN, "Cannot set SAX feature because outdated XML parser in classpath", feature, ame);
}
}
private static void trySetXercesSecurityManager(XMLReader xmlReader) {
// Try built-in JVM one first, standalone if not
for (String securityManagerClassName : new String[] {
"com.sun.org.apache.xerces.internal.util.SecurityManager",
"org.apache.xerces.util.SecurityManager"
}) {
try {
Object mgr = Class.forName(securityManagerClassName).newInstance();
Method setLimit = mgr.getClass().getMethod("setEntityExpansionLimit", Integer.TYPE);
setLimit.invoke(mgr, 4096);
xmlReader.setProperty("http://apache.org/xml/properties/security-manager", mgr);
// Stop once one can be setup without error
return;
} catch (Exception e) {
logger.log(POILogger.WARN, "SAX Security Manager could not be setup", e);
}
}
}
}