HADOOP-18575: followup: try to avoid repeatedly hitting exceptions when transformer factories do not support attributes (#5253)
Part of HADOOP-18469 and the hardening of XML/XSL parsers. Followup to the main HADOOP-18575 patch, to improve performance when working with xml/xsl engines which don't support the relevant attributes. Include this change when backporting. Contributed by PJ Fanning.
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@ -34,6 +34,7 @@
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import org.xml.sax.SAXException;
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import java.io.*;
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import java.util.concurrent.atomic.AtomicBoolean;
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/**
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* General xml utilities.
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@ -59,6 +60,11 @@ public class XMLUtils {
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public static final String VALIDATION =
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"http://xml.org/sax/features/validation";
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private static final AtomicBoolean CAN_SET_TRANSFORMER_ACCESS_EXTERNAL_DTD =
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new AtomicBoolean(true);
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private static final AtomicBoolean CAN_SET_TRANSFORMER_ACCESS_EXTERNAL_STYLESHEET =
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new AtomicBoolean(true);
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/**
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* Transform input xml given a stylesheet.
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*
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@ -143,8 +149,7 @@ public static TransformerFactory newSecureTransformerFactory()
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throws TransformerConfigurationException {
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TransformerFactory trfactory = TransformerFactory.newInstance();
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trfactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
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bestEffortSetAttribute(trfactory, XMLConstants.ACCESS_EXTERNAL_DTD, "");
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bestEffortSetAttribute(trfactory, XMLConstants.ACCESS_EXTERNAL_STYLESHEET, "");
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setOptionalSecureTransformerAttributes(trfactory);
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return trfactory;
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}
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@ -161,29 +166,45 @@ public static SAXTransformerFactory newSecureSAXTransformerFactory()
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throws TransformerConfigurationException {
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SAXTransformerFactory trfactory = (SAXTransformerFactory) SAXTransformerFactory.newInstance();
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trfactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
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bestEffortSetAttribute(trfactory, XMLConstants.ACCESS_EXTERNAL_DTD, "");
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bestEffortSetAttribute(trfactory, XMLConstants.ACCESS_EXTERNAL_STYLESHEET, "");
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setOptionalSecureTransformerAttributes(trfactory);
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return trfactory;
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}
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/**
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* These attributes are recommended for maximum security but some JAXP transformers do
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* not support them. If at any stage, we fail to set these attributes, then we won't try again
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* for subsequent transformers.
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*
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* @param transformerFactory to update
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*/
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private static void setOptionalSecureTransformerAttributes(
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TransformerFactory transformerFactory) {
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bestEffortSetAttribute(transformerFactory, CAN_SET_TRANSFORMER_ACCESS_EXTERNAL_DTD,
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XMLConstants.ACCESS_EXTERNAL_DTD, "");
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bestEffortSetAttribute(transformerFactory, CAN_SET_TRANSFORMER_ACCESS_EXTERNAL_STYLESHEET,
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XMLConstants.ACCESS_EXTERNAL_STYLESHEET, "");
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}
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/**
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* Set an attribute value on a {@link TransformerFactory}. If the TransformerFactory
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* does not support the attribute, the method just returns <code>false</code> and
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* logs the issue at debug level.
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*
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* @param transformerFactory to update
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* @param flag that indicates whether to do the update and the flag can be set to
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* <code>false</code> if an update fails
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* @param name of the attribute to set
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* @param value to set on the attribute
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* @return whether the attribute was successfully set
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*/
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static boolean bestEffortSetAttribute(TransformerFactory transformerFactory,
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String name, Object value) {
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try {
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transformerFactory.setAttribute(name, value);
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return true;
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} catch (Throwable t) {
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LOG.debug("Issue setting TransformerFactory attribute {}: {}", name, t.toString());
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static void bestEffortSetAttribute(TransformerFactory transformerFactory, AtomicBoolean flag,
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String name, Object value) {
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if (flag.get()) {
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try {
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transformerFactory.setAttribute(name, value);
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} catch (Throwable t) {
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flag.set(false);
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LOG.debug("Issue setting TransformerFactory attribute {}: {}", name, t.toString());
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}
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}
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return false;
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}
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}
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@ -20,6 +20,7 @@
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import java.io.InputStream;
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import java.io.StringReader;
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import java.io.StringWriter;
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import java.util.concurrent.atomic.AtomicBoolean;
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import javax.xml.XMLConstants;
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import javax.xml.parsers.DocumentBuilder;
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import javax.xml.parsers.SAXParser;
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@ -134,10 +135,16 @@ public void testExternalDtdWithSecureSAXTransformerFactory() throws Exception {
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@Test
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public void testBestEffortSetAttribute() throws Exception {
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TransformerFactory factory = TransformerFactory.newInstance();
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Assert.assertFalse("unexpected attribute results in return of false",
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XMLUtils.bestEffortSetAttribute(factory, "unsupportedAttribute false", "abc"));
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Assert.assertTrue("expected attribute results in return of false",
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XMLUtils.bestEffortSetAttribute(factory, XMLConstants.ACCESS_EXTERNAL_DTD, ""));
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AtomicBoolean flag1 = new AtomicBoolean(true);
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XMLUtils.bestEffortSetAttribute(factory, flag1, "unsupportedAttribute false", "abc");
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Assert.assertFalse("unexpected attribute results in return of false?", flag1.get());
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AtomicBoolean flag2 = new AtomicBoolean(true);
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XMLUtils.bestEffortSetAttribute(factory, flag2, XMLConstants.ACCESS_EXTERNAL_DTD, "");
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Assert.assertTrue("expected attribute results in return of true?", flag2.get());
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AtomicBoolean flag3 = new AtomicBoolean(false);
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XMLUtils.bestEffortSetAttribute(factory, flag3, XMLConstants.ACCESS_EXTERNAL_DTD, "");
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Assert.assertFalse("expected attribute results in return of false if input flag is false?",
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flag3.get());
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}
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private static InputStream getResourceStream(final String filename) {
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