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/*-
* ============LICENSE_START=======================================================
* Copyright (C) 2016-2018 Ericsson. All rights reserved.
* Modifications Copyright (C) 2020 Nordix Foundation.
* ================================================================================
* 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.
*
* SPDX-License-Identifier: Apache-2.0
* ============LICENSE_END=========================================================
*/
package org.onap.policy.apex.core.infrastructure.xml;
import java.io.InputStream;
import javax.xml.XMLConstants;
import javax.xml.namespace.QName;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.slf4j.ext.XLogger;
import org.slf4j.ext.XLoggerFactory;
import org.w3c.dom.Document;
/**
* A generic class for applying the XPATH queries on XML files.
*
* @author Sajeevan Achuthan (sajeevan.achuthan@ericsson.com)
*/
public class XPathReader {
// Logger for this class
private static final XLogger LOGGER = XLoggerFactory.getXLogger(XPathReader.class);
private String xmlFileName = null;
private InputStream xmlStream = null;
private Document xmlDocument;
private XPath xpath;
/**
* Construct Reader for the file passed in.
*
* @param xmlFileName the xml file name
*/
public XPathReader(final String xmlFileName) {
this.xmlFileName = xmlFileName;
init();
}
/**
* Construct Reader for the stream passed in.
*
* @param xmlStream a stream of XML
*/
public XPathReader(final InputStream xmlStream) {
this.xmlStream = xmlStream;
init();
}
/**
* Initialise the x-path reader.
*/
private void init() {
try {
LOGGER.info("Initializing XPath reader");
DocumentBuilderFactory df = DocumentBuilderFactory.newInstance();
df.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
df.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, "");
df.setAttribute(XMLConstants.ACCESS_EXTERNAL_SCHEMA, "");
// Check if this is operating on a file
if (xmlFileName != null) {
xmlDocument = df.newDocumentBuilder().parse(xmlFileName);
} else if (xmlStream != null) {
// Check if this is operating on a stream
xmlDocument = df.newDocumentBuilder().parse(xmlStream);
} else {
// We have an error
LOGGER.error("XPath reader not initialized with either a file or a stream");
return;
}
xpath = XPathFactory.newInstance().newXPath();
LOGGER.info("Initialized XPath reader");
} catch (final Exception ex) {
LOGGER.error("Error parsing XML file/stream from XPath reading, reason :\n" + ex.getMessage(), ex);
}
}
/**
* Read items from the file using xpath.
*
* @param expression x-path expression
* @param returnType XML node Set
* @return last node collected
*/
public Object read(final String expression, final QName returnType) {
try {
final XPathExpression xPathExpression = xpath.compile(expression);
return xPathExpression.evaluate(xmlDocument, returnType);
} catch (final XPathExpressionException ex) {
LOGGER.error("Failed to read XML file for XPath processing, reason:\n" + ex.getMessage(), ex);
return null;
}
}
}
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