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SDK for Microsoft Azure Storage Clients
/**
* Copyright Microsoft Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.microsoft.azure.storage.table;
import java.io.InputStream;
import java.io.Reader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import com.microsoft.azure.storage.Constants;
/**
* RESERVED FOR INTERNAL USE. An internal helper class used to parse objects from responses.
*/
final class DeserializationHelper {
// see use below for more explanation
private final static String ENTITY_EXPANSION_EXCEPTION_MESSAGE = "(.|\n)*Message: JAXP00010001: The parser has encountered more than \"\\d+\" entity expansions in this document; this is the limit imposed by the JDK\\.";
private static XMLInputFactory xmlif;
static {
setupXMLInputFactory();
}
/**
* Sets this class's XMLInputFactory instance to a new factory instance and sets the appropriate
* properties on it. This is not synchronized so multiple threads executing this will cause multiple factories to be
* created, but this is okay as it does not matter for the reader which factory creates it as they are functionally
* identical.
*/
public static void setupXMLInputFactory() {
final XMLInputFactory xmlif = XMLInputFactory.newInstance();
xmlif.setProperty(XMLInputFactory.IS_REPLACING_ENTITY_REFERENCES, Boolean.TRUE);
xmlif.setProperty(XMLInputFactory.IS_SUPPORTING_EXTERNAL_ENTITIES, Boolean.FALSE);
// set the IS_COALESCING property to true , if application desires to
// get whole text data as one event.
xmlif.setProperty(XMLInputFactory.IS_COALESCING, Boolean.TRUE);
DeserializationHelper.xmlif = xmlif;
}
/**
* Tests whether the provided exception is an entity expansion exception.
*
* Some versions of Java cause an exception to be incorrectly thrown when more XMLStreamReaders have been
* created by a single factory than the entity expansion limit property (default 64000). The default form of this
* exception is: "ParseError at [row,col]:[1,1]\n
* Message: JAXP00010001: The parser has encountered more than
* \"64000\" entity expansions in this document; this is the limit imposed by the JDK."
*
* @param e
* the XMLStreamException to test
* @return
* true if entity expansion exception, false otherwise
*/
public static boolean isEntityExpansionLimitException(XMLStreamException e) {
return e.getMessage() != null && e.getMessage().matches(ENTITY_EXPANSION_EXCEPTION_MESSAGE);
}
/**
* Creates an XML stream reader from the specified input stream.
*
* Some versions of Java cause an exception to be incorrectly thrown when more XMLStreamReaders have been
* created by a single factory than the entity expansion limit property (default 64000). This model catches
* that exception, creates a new factory with the appropriate settings, and then retries the reader creation.
*
* @param reader
* An InputStreamReader object that represents the input reader to use as the source.
*
* @return A java.xml.stream.XMLStreamReader object that represents the XML stream reader created from
* the specified input stream.
*
* @throws XMLStreamException
* If the XML stream reader could not be created.
* @see https://bugs.openjdk.java.net/browse/JDK-8028111
*/
public static XMLStreamReader createXMLStreamReaderFromReader(final Reader reader) throws XMLStreamException {
while (true) {
try {
return xmlif.createXMLStreamReader(reader);
}
catch (XMLStreamException e) {
if (isEntityExpansionLimitException(e)) {
setupXMLInputFactory();
}
else {
throw e;
}
}
}
}
/**
* Creates an XML stream reader from the specified input stream.
*
* Some versions of Java cause an exception to be incorrectly thrown when more XMLStreamReaders have been
* created by a single factory than the entity expansion limit property (default 64000). This model catches
* that exception, creates a new factory with the appropriate settings, and then retries the reader creation.
*
* @param streamRef
* An InputStream object that represents the input stream to use as the source.
*
* @return A java.xml.stream.XMLStreamReader object that represents the XML stream reader created from
* the specified input stream.
*
* @throws XMLStreamException
* If the XML stream reader could not be created.
*
* @see https://bugs.openjdk.java.net/browse/JDK-8028111
*/
public static XMLStreamReader createXMLStreamReaderFromStream(final InputStream streamRef)
throws XMLStreamException {
while (true) {
try {
return xmlif.createXMLStreamReader(streamRef, Constants.UTF8_CHARSET);
}
catch (XMLStreamException e) {
if (isEntityExpansionLimitException(e)) {
setupXMLInputFactory();
}
else {
throw e;
}
}
}
}
/**
* Reads character data for the specified XML element from an XML stream reader. This method will read start events,
* characters, and end events from a stream.
*
* @param xmlr
* An XMLStreamReader object that represents the source XML stream reader.
*
* @param elementName
* A String that represents XML element name.
*
* @return A String that represents the character data for the specified element.
*
* @throws XMLStreamException
* If an XML stream failure occurs.
*/
public static String readElementFromXMLReader(final XMLStreamReader xmlr, final String elementName)
throws XMLStreamException {
return readElementFromXMLReader(xmlr, elementName, true);
}
/**
* Reads character data for the specified XML element from an XML stream reader. This method will read start events,
* characters, and end events from a stream.
*
* @param xmlr
* An XMLStreamReader object that represents the source XML stream reader.
*
* @param elementName
* A String that represents XML element name.
* @param returnNullOnEmpty
* If true, returns null when a empty string is read, otherwise EmptyString ("") is returned.
*
* @return A String that represents the character data for the specified element.
*
* @throws XMLStreamException
* If an XML stream failure occurs.
*/
public static String readElementFromXMLReader(final XMLStreamReader xmlr, final String elementName,
boolean returnNullOnEmpty) throws XMLStreamException {
xmlr.require(XMLStreamConstants.START_ELEMENT, null, elementName);
int eventType = xmlr.next();
final StringBuilder retVal = new StringBuilder();
if (eventType == XMLStreamConstants.CHARACTERS) {
// This do while is in case the XMLStreamReader does not have
// the IS_COALESCING property set
// to true which may result in text being read in multiple events
// If we ensure all xmlreaders have this property we can optimize
// the StringBuilder and while loop
// away
do {
retVal.append(xmlr.getText());
eventType = xmlr.next();
} while (eventType == XMLStreamConstants.CHARACTERS);
}
xmlr.require(XMLStreamConstants.END_ELEMENT, null, elementName);
if (retVal.length() == 0) {
return returnNullOnEmpty ? null : Constants.EMPTY_STRING;
}
else {
return retVal.toString();
}
}
/**
* Private Default Ctor
*/
private DeserializationHelper() {
// No op
}
}
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